Timolol-Brimonidin-Dorzolamide (timolol maleate/brimonidine tartrate/dorzolamide HCl/PF)

Dosage and concentration of dorzolamide hydrochloride are expressed in terms of dorzolamide.

For the treatment of open-angle glaucoma or ocular hypertension in adults and pediatric patients, the usual dosage of dorzolamide is 1 drop of a 2% ophthalmic solution in the affected eye(s) 3 times daily.

If the target intraocular pressure (IOP) is not achieved, alternative or additional ocular hypotensive agents may be required. (See Uses: Ocular Hypertension and Glaucoma.) When dorzolamide is used in fixed combination with timolol for the treatment of open-angle glaucoma or ocular hypertension in adults and pediatric patients 2 years of age or older, the usual dosage is 1 drop of an ophthalmic solution containing dorzolamide 2% and timolol 0.5% in the affected eye(s) twice daily. Because of the potential for additive systemic effects, combined use of topical dorzolamide and an oral carbonic anhydrase inhibitor (e.g., acetazolamide, dichlorphenamide, methazolamide) is not recommended by the manufacturer.

Topical dorzolamide has not been evaluated in patients with severe renal impairment (i.e., creatinine clearance less than 30 mL/minute). Because dorzolamide and N-desethyldorzolamide are eliminated principally via renal excretion, the manufacturer states that topical ocular use of the drug in patients with severe renal impairment is not recommended.

Topical dorzolamide has not been evaluated in patients with hepatic impairment, and the manufacturer states that the drug should be used with caution in such patients.

Brimonidine tartrate is applied topically to the eye as an ophthalmic solution. Brimonidine tartrate also is commercially available in fixed combination with brinzolamide (as an ophthalmic suspension) and in fixed combination with timolol (as an ophthalmic solution) for topical application to the eye.

Although topical brimonidine has been administered twice daily as an ocular hypotensive agent in certain clinical studies, reductions in intraocular pressure (IOP) induced by the drug appear to diminish 8 hours following administration. Therefore, the manufacturers recommend administering brimonidine tartrate 0.1, 0.15, or 0.2% ophthalmic solution 3 times daily at intervals of approximately 8 hours. The fixed-combination ophthalmic suspension containing brinzolamide and brimonidine tartrate also is administered 3 times daily. However, when used in fixed combination with timolol, brimonidine is administered twice daily at intervals of approximately 12 hours. For self-medication for temporary relief of ocular redness, brimonidine tartrate 0.025% may be administered up to 4 times daily.

The fixed-combination ophthalmic suspension containing brinzolamide and brimonidine tartrate should be shaken well prior to use.

Care should be taken to avoid contamination of the dispensing container. (See Bacterial Keratitis under Cautions: Warnings/Precautions.)

Some brimonidine ophthalmic preparations contain benzalkonium chloride, which may be absorbed by soft contact lenses. Contact lenses should be removed prior to administration of each dose of these preparations, but may be reinserted 15 minutes after the dose. The manufacturer of brimonidine tartrate 0.025% ophthalmic solution states that contact lenses may be reinserted 10 minutes after the dose.

If the patient is receiving more than one topical ophthalmic preparation, the preparations should be administered at least 5 minutes apart.

Timolol or timolol maleate is applied topically to the eye as an ophthalmic solution. Timolol maleate also is applied topically to the eye as a gel-forming ophthalmic solution. Timolol maleate also is commercially available in fixed combination with dorzolamide hydrochloride or brimonidine tartrate (as ophthalmic solutions) for topical application to the eye. Care should be taken to avoid contamination of the solution container.

Some timolol ophthalmic solutions contain benzalkonium chloride, which may be absorbed by soft contact lenses. Contact lenses should be removed prior to administration of each dose of these solutions, but may be reinserted 15 minutes after the dose.

Preservative-free ophthalmic solutions containing timolol alone or in fixed combination with dorzolamide should be administered topically to one or both eyes immediately after the single-use container is opened; since sterility cannot be maintained after the individual unit is opened, any remaining contents should be discarded immediately after administration.

If the patient is receiving more than one ophthalmic preparation, the preparations should be administered at least 5 minutes apart, although some manufacturers recommend an interval of at least 10 minutes. Containers of timolol maleate ophthalmic gel-forming solution should be inverted and shaken once just prior to administration of each dose. Patients receiving ophthalmic gel-forming solutions of the drug who also are receiving other ophthalmic preparations should be instructed that other topical preparations be administered at least 10 minutes before a dose of the gel-forming solution.

Dorzolamide hydrochloride is applied topically to the eye as an ophthalmic solution. Dorzolamide hydrochloride also is commercially available in fixed combination with timolol maleate for topical application to the eye as an ophthalmic solution.

Care should be taken to avoid contamination of the solution container. (See Cautions: Precautions and Contraindications.)

Dorzolamide ophthalmic solution and some formulations of dorzolamide and timolol ophthalmic solution contain benzalkonium chloride, which may be absorbed by soft contact lenses. Contact lenses should be removed prior to topical application of each dose of these preparations, but may be reinserted 15 minutes after the dose.

Preservative-free dorzolamide and timolol ophthalmic solution in single-use containers should be administered topically to one or both eyes immediately after the container is opened; since sterility cannot be maintained after the individual unit is opened, any remaining contents should be discarded immediately after administration.

If the patient is receiving more than one ophthalmic preparation, the preparations should be administered at least 5 minutes apart.

No dosing information is available for this tab.

No dosing information is available for this tab.

No formal drug interaction studies have been performed.

There are no contraindication interactions for this drug.

Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

Agents That Affect Catecholamines/Iobenguane I 123

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Many compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells.(1)

CLINICAL EFFECTS: Compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with imaging completed with iobenguane.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discuss the use of agents that affect catecholamines. Discontinue drugs that reduce catecholamine uptake or deplete catecholamine stores prior to imaging with iobenguane. Before imaging with iobenguane, discontinue agents that affect catecholamines for at least 5 biological half-lives, as clinically tolerated.(1)

DISCUSSION: Many agents may reduce catecholamine uptake or deplete catecholamine stores.(1) Examples include: - CNS stimulants or amphetamines (e.g. cocaine, methylphenidate, dextroamphetamine) - norepinephrine and dopamine reuptake inhibitors (e.g. phentermine) - norepinephrine and serotonin reuptake inhibitors (e.g. tramadol) - monoamine oxidase inhibitors (e.g. phenelzine, linezolid) - central monoamine depleting drugs (e.g. reserpine) - non-select beta adrenergic blocking drugs (e.g. labetalol) - alpha agonists or alpha/beta agonists (e.g. pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline) - tricyclic antidepressants or norepinephrine reuptake inhibitors (e.g. amitriptyline, bupropion, duloxetine, mirtazapine, venlafaxine) - botanicals that may inhibit reuptake of norepinephrine, serotonin or dopamine (e.g. ephedra, ma huang, St. John's Wort, yohimbine)

Agents That Affect Catecholamines/Iobenguane I 131

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Many compounds that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells.(1)

CLINICAL EFFECTS: Compounds that reduce catecholamine uptake or that deplete catecholamine stores may impact the dosimetry calculations or effectiveness of iobenguane.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Discuss the use of agents that affect catecholamines. Discontinue drugs that reduce catecholamine uptake or deplete catecholamine stores for at least 5 half-lives before administration of either the dosimetry or a therapeutic dose of iobenguane. Do not administer these drugs until at least 7 days after each iobenguane dose.(1)

DISCUSSION: Many agents may reduce catecholamine uptake or deplete catecholamine stores.(1) Examples include: - CNS stimulants or amphetamines (e.g. cocaine, methylphenidate, dextroamphetamine) - norepinephrine and dopamine reuptake inhibitors (e.g. phentermine) - norepinephrine and serotonin reuptake inhibitors (e.g. tramadol) - monoamine oxidase inhibitors (e.g. phenelzine, linezolid) - central monoamine depleting drugs (e.g. reserpine) - non-select beta adrenergic blocking drugs (e.g. labetalol) - alpha agonists or alpha/beta agonists (e.g. pseudoephedrine, phenylephrine, ephedrine, phenylpropanolamine, naphazoline) - tricyclic antidepressants or norepinephrine reuptake inhibitors (e.g. amitriptyline, bupropion, duloxetine, mirtazapine, venlafaxine) - botanicals that may inhibit reuptake of norepinephrine, serotonin or dopamine (e.g. ephedra, ma huang, St. John's Wort, yohimbine) - calcium channel blockers

Beta-Blockers (NONSELECTIVE)/Methyldopa

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Unopposed alpha-adrenergic vasoconstriction produced by alpha-methylnorepinephrine in the presence of beta-blockade.

CLINICAL EFFECTS: Severe hypertension.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Monitor blood pressure during concomitant administration of methyldopa and a nonselective beta-blocker. If hypertension occurs, treatment with phentolamine should be considered.

DISCUSSION: Although methyldopa and propranolol have been used together to treat hypertension, severe increases in blood pressure, including death in one patient, has been reported during administration of these drugs. In addition, methyldopa alone has been reported to cause paradoxical hypertension. Additional studies are needed to define the specific population at risk.

Non-Cardioselective Beta-Blockers/Beta-2 Agonists

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Non-cardioselective beta-blockers and beta-2 agonists may antagonize the effects of each other.

CLINICAL EFFECTS: Diminished response to either the beta-agonist, beta-blocker, or both may occur. Beta-blockers may also induce bronchospasm.

PREDISPOSING FACTORS: Patients receiving beta-2 agonists for the treatment of asthma may be more at risk for bronchospasm.

PATIENT MANAGEMENT: If possible, avoid beta-blocker therapy in asthmatic patients requiring beta-2 agonist therapy. If beta-blocker therapy is required, use a cardio-selective beta-blocker. For timolol ophthalmic drops, counsel patients to apply pressure to the inner corner of the eye after administration to prevent systemic absorption. Monitor patients for decreased effects of either agent, such as increased need for/use of beta-2 agonists or increased heart rate or blood pressure.

DISCUSSION: Many patients with asymptomatic or mild reactive airways disease tolerate beta-blockers well. Most patients with COPD do not have bronchospastic component to their illness and may be given beta-blockers. Heart failure treatment guidelines recommend beta-blockers in the presence of COPD. Non-selective beta-blockers have been shown to have a negative effect on lung function (FEV1) and airway hyperresponsiveness (AHR) in patients with asthma and COPD.(1) An open-label study using the nonselective beta blocker nadolol showed no effect on salbutamol in 10 patients with mild asthma not on controller therapy.(2) A study in 8 healthy men showed that long acting propranolol (160 mg) only effected airway dilation at the 200 mcg salbutamol dose. The 800 mcg and 1600 mcg dose were unaffected. However, penbutolol prevented any significant airway dilation with all doses of salbutamol.(3) In a double blind, three-way, crossover study, 44% (7/16 patients) of patients taking metoprolol showed a greater than 20% decrease in FEV1 compared to 19% (3 patients) after dilevalol and 6% (1 patient) after placebo. Dilevalol and metoprolol significantly inhibited isoproterenol response compared to placebo.(4) A double-blind, randomized, crossover study in 10 asthmatic patients showed that intravenous propranolol produced marked symptomatic bronchoconstriction. Only a slight but significant inhibition of bronchomotor sensitivity to isoproterenol was noted during esmolol infusion.(5) In 18 patients with reversible bronchial asthma, labetalol caused a significant increase in FEV1 and metoprolol caused a significant decrease in FEV1. Concurrent administration of isoproterenol and labetalol caused a further increase in FEV1. The effect of isoproterenol was decreased by metoprolol (100, 200mg).(6) In one study propranolol (0.06mg/kg IV) was shown to almost completely block the effects of isoproterenol in asthmatics. Metoprolol (0.12mg/kg IV) did not affect isoproterenol.(7) Studies have shown that cardioselective beta-blockers are safe for patients with asthma and COPD.(8,9,10) Nebivolol and celiprolol significantly decreased FEV1. Inhalation of albuterol (up to 800mcg) significantly improved FEV1, but the values after nebivolol and celiprolol administration were lower than the initial values.(11) Administration of metoprolol did not cause any respiratory problems in 9 asthmatic patients. There was no significant difference between the metoprolol and placebo groups in the respiratory response to an isoproterenol aerosol in 24 asthmatic patients.(12) Eight male asthmatic patients were given 10 mg bisoprolol, 20 mg bisoprolol, and 100 mg metoprolol. Both bisoprolol and metoprolol caused bronchoconstriction measured by a significant fall in PEFR (peak expiratory flow rate). Terbutaline was able to reverse bronchoconstriction in all patients.(13) A double blind, placebo-controlled study analyzed the use of atenolol 100mg, metoprolol 100mg, or acebutolol 400 mg in 8 asthmatic patients before and after exercise. All three drugs reduced significantly FEV1 and PEFR. Administration of terbutaline improved all respiratory indices.(14) A double-blind crossover trial in 10 asthmatic patients showed that a single IV dose of atenolol 3mg caused slight impairment of ventilatory function. A dose of salbutamol by inhalation was able to reverse the bronchial effect of atenolol.(15) Propranolol (80mg/day), oxprenolol (80mg/day), atenolol (100mg/day), and celiprolol 200mg/day were given to 10 asthmatic patients in a randomized, crossover design with a two week washout period between each drug. The non-beta 1 selective beta blockers (propranolol, oxprenolol) caused a significant reduction in FEV1 and inhibited the bronchodilator response to inhaled salbutamol. Atenolol and celiprolol (beta1 selective beta blockers) did not significantly affect respiratory function or antagonize salbutamol effects.(16) A double blind, randomized, within patient, placebo-controlled study compared the cardioselective beta-blocker atenolol to the non-selective propranolol. Atenolol caused a significantly less drop in FEV1 compared to propranolol. The effect of isoprenaline plus the beta blockers were also studied. Both atenolol and propranolol effected isoprenaline FEV1 dose response curves but the greatest displacement was seen with propranolol.(17) The pulmonary effects of celiprolol 200 mg, celiprolol 400mg, propranolol 40mg, atenolol 100 mg were evaluated in 34 asthmatic patients. Propranolol and atenolol caused significant reductions in pulmonary function. Propranolol pretreatment caused a significant reduction in the effect of the bronchodilator. Celiprolol did not antagonize the bronchodilators.(18) A double-blind, placebo controlled, randomized, crossover design study studied the effects of propranolol 80mg or celiprolol 200 or 400mg on pulmonary function. Propranolol produced a significant decrease in FEV1 and FVC. Celiprolol and placebo had similar results. The effect of aerosolized terbutaline was also measured. Even at supratherapeutic doses, terbutaline was unable to restore pulmonary function parameters to baseline levels after treatment with propranolol. Terbutaline caused further bronchodilation after administration of celiprolol.(19) Eleven asthmatic patients showed significant bronchoconstriction in small airways after propranolol 40mg and pindolol 2.5mg in a double blind, randomized trial. Large airways only showed bronchoconstriction with propranolol. Terbutaline 0.5mg subcutaneous was given after pretreatment with propranolol and pindolol. The bronchodilator effect of terbutaline on large airways was diminished after both propranolol and timolol.(20)

Non-Cardioselective Beta-Blockers/Salmeterol

SEVERITY LEVEL: 2-Severe Interaction: Action is required to reduce the risk of severe adverse interaction.

MECHANISM OF ACTION: Non-cardioselective beta-blockers and beta-2 agonists may antagonize the effects of each other.

CLINICAL EFFECTS: Diminished response to either the beta-agonist, beta-blocker, or both may occur. Beta-blockers may also induce bronchospasm.

PREDISPOSING FACTORS: Patients receiving beta-2 agonists for the treatment of asthma may be more at risk for bronchospasm.

PATIENT MANAGEMENT: If possible, avoid beta-blocker therapy in asthmatic patients requiring beta-2 agonist therapy. If beta-blocker therapy is required, use a cardio-selective beta-blocker. Monitor patients for decreased effects of either agent, such as increased need for/use of beta-2 agonists or increased heart rate or blood pressure.

DISCUSSION: Many patients with asymptomatic or mild reactive airways disease tolerate beta-blockers well. Most patients with COPD do not have bronchospastic component to their illness and may be given beta-blockers. Heart failure treatment guidelines recommend beta-blockers in the presence of COPD. Non-selective beta-blockers have been shown to have a negative effect on lung function (FEV1) and airway hyperresponsiveness (AHR) in patients with asthma and COPD.(1) An open-label study using the nonselective beta blocker nadolol showed no effect on salbutamol in 10 patients with mild asthma not on controller therapy.(2) A study in 8 healthy men showed that long acting propranolol (160 mg) only effected airway dilation at the 200 mcg salbutamol dose. The 800 mcg and 1600 mcg dose were unaffected. However, penbutolol prevented any significant airway dilation with all doses of salbutamol.(3) In a double blind, three-way, crossover study, 44% (7/16 patients) of patients taking metoprolol showed a greater than 20% decrease in FEV1 compared to 19% (3 patients) after dilevalol and 6% (1 patient) after placebo. Dilevalol and metoprolol significantly inhibited isoproterenol response compared to placebo.(4) A double-blind, randomized, crossover study in 10 asthmatic patients showed that intravenous propranolol produced marked symptomatic bronchoconstriction. Only a slight but significant inhibition of bronchomotor sensitivity to isoproterenol was noted during esmolol infusion.(5) In 18 patients with reversible bronchial asthma, labetalol caused a significant increase in FEV1 and metoprolol caused a significant decrease in FEV1. Concurrent administration of isoproterenol and labetalol caused a further increase in FEV1. The effect of isoproterenol was decreased by metoprolol (100, 200mg).(6) In one study propranolol (0.06mg/kg IV) was shown to almost completely block the effects of isoproterenol in asthmatics. Metoprolol (0.12mg/kg IV) did not affect isoproterenol.(7) Studies have shown that cardioselective beta-blockers are safe for patients with asthma and COPD.(8,9,10) Nebivolol and celiprolol significantly decreased FEV1. Inhalation of albuterol (up to 800mcg) significantly improved FEV1, but the values after nebivolol and celiprolol administration were lower than the initial values.(11) Administration of metoprolol did not cause any respiratory problems in 9 asthmatic patients. There was no significant difference between the metoprolol and placebo groups in the respiratory response to an isoproterenol aerosol in 24 asthmatic patients.(12) Eight male asthmatic patients were given 10 mg bisoprolol, 20 mg bisoprolol, and 100 mg metoprolol. Both bisoprolol and metoprolol caused bronchoconstriction measured by a significant fall in PEFR (peak expiratory flow rate). Terbutaline was able to reverse bronchoconstriction in all patients.(13) A double blind, placebo-controlled study analyzed the use of atenolol 100mg, metoprolol 100mg, or acebutolol 400 mg in 8 asthmatic patients before and after exercise. All three drugs reduced significantly FEV1 and PEFR. Administration of terbutaline improved all respiratory indices.(14) A double-blind crossover trial in 10 asthmatic patients showed that a single IV dose of atenolol 3mg caused slight impairment of ventilatory function. A dose of salbutamol by inhalation was able to reverse the bronchial effect of atenolol.(15) Propranolol (80mg/day), oxprenolol (80mg/day), atenolol (100mg/day), and celiprolol 200mg/day were given to 10 asthmatic patients in a randomized, crossover design with a two week washout period between each drug. The non-beta 1 selective beta blockers (propranolol, oxprenolol) caused a significant reduction in FEV1 and inhibited the bronchodilator response to inhaled salbutamol. Atenolol and celiprolol (beta1 selective beta blockers) did not significantly affect respiratory function or antagonize salbutamol effects.(16) A double blind, randomized, within patient, placebo-controlled study compared the cardioselective beta-blocker atenolol to the non-selective propranolol. Atenolol caused a significantly less drop in FEV1 compared to propranolol. The effect of isoprenaline plus the beta blockers were also studied. Both atenolol and propranolol effected isoprenaline FEV1 dose response curves but the greatest displacement was seen with propranolol.(17) The pulmonary effects of celiprolol 200 mg, celiprolol 400mg, propranolol 40mg, atenolol 100 mg were evaluated in 34 asthmatic patients. Propranolol and atenolol caused significant reductions in pulmonary function. Propranolol pretreatment caused a significant reduction in the effect of the bronchodilator. Celiprolol did not antagonize the bronchodilators.(18) A double-blind, placebo controlled, randomized, crossover design study studied the effects of propranolol 80mg or celiprolol 200 or 400mg on pulmonary function. Propranolol produced a significant decrease in FEV1 and FVC. Celiprolol and placebo had similar results. The effect of aerosolized terbutaline was also measured. Even at supratherapeutic doses, terbutaline was unable to restore pulmonary function parameters to baseline levels after treatment with propranolol. Terbutaline caused further bronchodilation after administration of celiprolol.(19) Eleven asthmatic patients showed significant bronchoconstriction in small airways after propranolol 40mg and pindolol 2.5mg in a double blind, randomized trial. Large airways only showed bronchoconstriction with propranolol. Terbutaline 0.5mg subcutaneous was given after pretreatment with propranolol and pindolol. The bronchodilator effect of terbutaline on large airways was diminished after both propranolol and timolol.(20)

Moderate Interaction: Assess the risk to the patient and take action as needed.

Beta-Blockers/Clonidine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Withdrawal of clonidine triggers increased catecholamine release. Beta-blockers inhibit the vasodilation mediated by the beta 2 receptor, leaving the vasoconstriction mediated by the alpha 2 receptor unopposed. In addition, concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

CLINICAL EFFECTS: Severe hypertension may occur upon abrupt discontinuation of clonidine in patients receiving both clonidine and beta-blockers. In addition, concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: In a patient receiving both drugs, discontinuation of the beta-blocker prior to clonidine may decrease the occurrence of rebound hypertension. If clonidine is discontinued first, rebound hypertension can be treated by restarting the clonidine or by the IV administration of phentolamine, phenoxybenzamine or prazosin. When adding either of these agents to the drug regimen of the patient, monitor blood pressure. Since labetalol has both alpha and beta activity, administration of labetalol may prevent rebound hypertension in patients undergoing clonidine withdrawal, although conflicting reports exist. In addition, concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

DISCUSSION: Increased blood pressure has been observed in patients following: 1) the discontinuation of clonidine in patients receiving beta-blockers, 2) the replacement of clonidine therapy with beta-blockers, 3) the simultaneous discontinuation of both drugs. Conflicting reports exist on the development of increased blood pressure after clonidine withdrawal in patients receiving labetalol. Patients receiving labetalol who are being withdrawn from clonidine should still be closely monitored.

Beta-Blockers/Moxonidine

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Withdrawal of moxonidine triggers increased catecholamine release. Beta-blockers inhibit the vasodilation mediated by the beta 2 receptor, leaving the vasoconstriction mediated by the alpha 2 receptor unopposed. In addition, concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

CLINICAL EFFECTS: Severe hypertension may occur upon abrupt discontinuation of moxonidine in patients receiving both moxonidine and beta-blockers. In addition, concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: If combination therapy with moxonidine and a beta-blocker is to be ceased, the beta-blocker should be stopped first to decrease the risk of rebound hypertension. Moxonidine may be stopped after a few days have elapsed. During cessation of therapy blood pressure should be regularly monitored. If moxonidine is discontinued first, rebound hypertension can be treated by restarting the moxonidine or by the IV administration of phentolamine, phenoxybenzamine or prazosin. Since labetalol has both alpha and beta activity, administration of labetalol may prevent rebound hypertension in patients undergoing moxonidine withdrawal, although conflicting reports exist. When adding either of these agents to the drug regimen of the patient, monitor blood pressure. Concurrent use is expected to produce additive effects on blood pressure and heart rate requiring standard monitoring precautions.

DISCUSSION: Abrupt cessation of combination therapy with moxonidine and a beta-blocker may result in rebound hypertension. Withdrawal of moxonidine may trigger increased catecholamine release. Beta-blockers inhibit the vasodilation mediated by the beta 2 receptor, leaving the vasoconstriction mediated by the alpha 2 receptor unopposed.

Dorzolamide/Carbonic Anhydrase Inhibitors

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Dorzolamide and other carbonic anhydrase inhibitors cause a decrease in aqueous humor secretion by slowing the formation of bicarbonate ions with a subsequent reduction of sodium and fluid transport which results in a reduction of intraocular pressure.(1)

CLINICAL EFFECTS: If dorzolamide is given with other carbonic anhydrase inhibitors it may cause electrolyte disturbances, because dorzolamide can be absorbed systemically.(1)

PREDISPOSING FACTORS: Patients with conditions that predispose to acidosis (such as renal disease, severe respiratory disorders, status epilepticus, diarrhea, and being on a ketogenic diet) may be at increased risk of experiencing adverse effects from concurrent carbonic anhydrase inhibitors.

PATIENT MANAGEMENT: The manufacturer of dorzolamide states that concurrent use with oral carbonic anhydrase inhibitors is not recommended.(1)

DISCUSSION: Although no human data is available, electrolyte imbalance, development of an acidotic state, and possible nervous system effects may occur following administration of dorzolamide and oral carbonic anhydrase inhibitors.(1)

Selected Beta-Blockers/Selected Alpha-Blockers

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Alpha-blockers may cause syncope with sudden loss of consciousness secondary to excessive postural hypotension. Following the first dose of an alpha-blocker, compensatory tachycardia helps to prevent or limit syncope. Beta-blockers may inhibit this tachycardia, thereby worsening alpha-blocker induced hypotension.

CLINICAL EFFECTS: The hypotensive effects of an alpha-blocker may be increased in patients on concurrent beta-blocker therapy.

PREDISPOSING FACTORS: Patients may be at increased risk of postural hypotension with concurrent diuretic therapy and those on low-sodium diets.

PATIENT MANAGEMENT: When starting alpha-blocker therapy in patients receiving beta-blockers, consider initiating treatment with a reduced dose of the alpha-blocker. If syncope occurs, provide supportive treatment as necessary. The adverse effect is self limiting and in most cases does not recur after the initial period of therapy or during subsequent dose titration with the alpha-blocker.

DISCUSSION: Beta-blockers increase the acute postural hypotension that frequently follows the first dose of an alpha-blocker. Initiation of beta-blocker therapy in patients that have started taking an alpha-blocker would not be expected to produce acute postural hypotension. Alpha-blockers linked to this interaction include alfuzosin, doxazosin, prazosin, and terazosin. Beta-blockers linked to this interaction include acebutolol, atenolol, betaxolol, bevantolol, levobunolol, metoprolol, nadolol, pindolol, pronethalol, propranolol, and timolol.

Selected Beta-Blockers/Selected Calcium Channel Blockers

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Synergistic pharmacologic activity.

CLINICAL EFFECTS: May see an increase in the therapeutic and toxic effects of both drugs. Concurrent use in patients with low heart rates may unmask sick sinus syndrome.

PREDISPOSING FACTORS: Preexisting left ventricular dysfunction and high doses of the beta-blocking agent may predispose patients to adverse responses to this drug combination. Other possible factors include parenteral administration and concurrent administration of other cardio-depressant drugs such as antiarrhythmics.

PATIENT MANAGEMENT: Monitor the patient for signs of increased cardio-depressant effects and hypotension. Adjust the dose accordingly.

DISCUSSION: Coadministration of these classes of drugs may be effective in the treatment of angina pectoris and hypertension. Patients should be screened in order to determine who should receive this combination of agents. The concurrent use of mibefradil and beta-blockers in patients with low heart rates may unmask underlying sick sinus syndrome. One or more of the drug pairs linked to this monograph have been included in a list of interactions that could be considered for classification as "non-interruptive" in EHR systems. This DDI subset was vetted by an expert panel commissioned by the U.S. Office of the National Coordinator (ONC) for Health Information Technology.

Selected Beta-Blockers/Theophyllines

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Certain beta-blockers may inhibit theophylline metabolism. In addition, beta-blockers, especially non-selective agents, can antagonize the pharmacologic effects of theophylline.

CLINICAL EFFECTS: Even though theophylline concentrations may increase leading to increased possibility of theophylline toxicity, beta-blockers decrease theophylline's therapeutic effects.

PREDISPOSING FACTORS: Cigarette smoking may exacerbate this interaction.

PATIENT MANAGEMENT: Avoid the use of non-selective beta-blockers with theophylline. If a beta-blocker must be used, a cardioselective agent that does not decrease the clearance of theophylline (e.g., atenolol) should be considered. However, since cardioselectivity is not absolute and is less selective at higher doses, cardioselective beta-blockers should be used with caution in patients with bronchospastic disease.

DISCUSSION: Inhibition of theophylline metabolism is greatest with lipophilic beta-blockers undergoing hepatic metabolism (e.g., propranolol). Additionally, the decrease in theophylline clearance appears to be dose dependent as the higher the beta-blocker dose, the greater the decrease in theophylline clearance. If the patient is on both drugs and the beta-blocker is discontinued, serum theophylline concentrations may decrease. In these cases, monitor for a decrease in theophylline therapeutic effect and adjust the dose as needed.

Slt Ophth Non-Cardioselective Beta-Blockers/Antidiabetics

SEVERITY LEVEL: 3-Moderate Interaction: Assess the risk to the patient and take action as needed.

MECHANISM OF ACTION: Not fully established. Probably blockade of a variety of beta-adrenergic responses to hypoglycemia.(1,2)

CLINICAL EFFECTS: Diminished response to sulfonylureas and insulin may occur. Frequency and severity of hypoglycemic episodes may be increased, while warning symptoms of low blood sugar may be masked.(1,2)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Try to avoid beta-blocker therapy, particularly in diabetics prone to hypoglycemic attacks. One of the cardioselective agents may decrease risk of hypertensive attacks and allow more rapid glucose recovery from hypoglycemia. Patients should be counseled not to rely on tachycardia to diagnose hypoglycemia, since it is masked by beta-blocker therapy. Diaphoresis is unaffected by beta-blockade and can be used by the diabetic to recognize hypoglycemia.

DISCUSSION: A double blind, randomized, 12 month study of 39 patients tested the metabolic effects of pindolol (5mg BID) compared to control group on insulin sensitivity. The patient's insulin sensitivity index decreased 17% when on pindolol treatment compared to placebo (p<0.01). Insulin mediated glucose uptake was significantly lower (p<0.05) with propranolol treatment than with placebo.(3) A study of 26 patients with chronic heart failure showed that carvedilol (average daily dose 27.5mg/d) caused a significant decrease in fasting insulin levels (17.09 to 10.77 microU/ml, p <0.05) compared to pre-treatment levels. This trial also showed that patients on carvedilol had significantly (p=0.015) lower fasting insulin levels (10.77 microU/ml) compared to the fasting insulin levels (20.72 microU/ml) of patients on bisoprolol treatment (5.9mg/d).(4) There have been case reports of hypoglycemia following the addition of ophthalmic timolol to a diabetic regimen.(5-7) Studies have shown that ophthalmic beta-blockers, especially the aqueous solution, have significant systemic absorption and do not undergo first-pass metabolism.(8,9)

Brimonidine is contraindicated in neonates and infants younger than 2 years of age. (See Pediatric Use under Warnings/Precautions: Specific Populations, in Cautions.) Brimonidine also is contraindicated in patients with known hypersensitivity to the drug or any ingredient in the formulation.

• Acute decompensated heart failure
• Asthma
• Cardiogenic shock
• Complete atrioventricular block
• Incomplete AV heart block
• Sinus bradycardia

• Chronic obstructive pulmonary disease
• Hyperthyroidism

• Buerger's disease
• Cerebrovascular disorder
• Depression
• Diabetes mellitus
• Hypoglycemic disorder
• Myasthenia gravis
• No disease contraindications
• Orthostatic hypotension
• Raynaud's phenomenon

Adverse effects reported in approximately 10-30% of patients receiving brimonidine tartrate 0.1-0.2% ophthalmic solution include oral dryness, ocular or conjunctival hyperemia, burning and stinging, allergic conjunctivitis, headache, blurring, foreign body sensation, fatigue/drowsiness, conjunctival follicles, ocular allergic reactions, and ocular pruritus. In addition, corneal staining/erosion, photophobia, eyelid erythema, ocular ache/pain, ocular dryness, tearing, upper respiratory symptoms, eyelid edema, conjunctival edema, dizziness, blepharitis, ocular irritation, GI symptoms, hypertension, asthenia, conjunctival blanching, abnormal vision, visual disturbances, and muscular pain have been reported in approximately 3-9% of patients receiving brimonidine tartrate 0.1-0.2% ophthalmic solution.

Adverse effects reported in approximately 1-4% of patients receiving brimonidine tartrate 0.025% ophthalmic solution include decreased visual acuity, conjunctival or ocular hyperemia, dry eye, instillation site pain, and headache.

More Frequent

• Conjunctival hyperemia
• Follicular conjunctivitis
• Headache disorder
• Ocular itching
• Ocular itching
• Ocular redness

Less Frequent

• Blepharitis
• Blurred vision
• Chemosis
• Chest pain
• Conjunctival hemorrhage
• Conjunctivitis
• Corneal erosion
• Depression
• Diabetes mellitus
• Dizziness
• Eyelid edema
• Gastrointestinal irritation
• Hypertension
• Mucopurulent conjunctivitis
• Myalgia
• Nasal congestion
• Nausea
• Ocular discomfort
• Ocular pain
• Rhinitis
• Sneezing
• Syncope
• Visual changes
• Vitreous detachment
• Vomiting

Rare or Very Rare

• Acute myocardial infarction
• Acute respiratory failure
• Agranulocytosis
• Anaphylaxis
• Angioedema
• Angioedema
• Aplastic anemia
• Bradycardia
• Bradycardia
• Bronchospastic pulmonary disease
• Bronchospastic pulmonary disease
• Cardiac arrhythmia
• Cerebrovascular accident
• Choroidal detachment
• Choroidal detachment
• Contact dermatitis
• Cystoid macular edema
• Decreased corneal sensitivity
• Dyspnea
• Epistaxis
• Heart block
• Heart failure
• Hepatic necrosis
• Hypertension
• Hypotension
• Iridocyclitis
• Keratitis
• Muscle weakness
• Myopia
• Ocular pain
• Paresthesia
• Peyronie's disease
• Skin rash
• Sore throat
• Stevens-johnson syndrome
• Systemic lupus erythematosus
• Toxic epidermal necrolysis
• Urolithiasis

More Frequent

• Allergic conjunctivitis
• Drowsy
• Dysgeusia
• Eye tearing
• Eyelid erythema
• Fatigue
• Ocular irritation
• Ocular irritation
• Ocular itching
• Punctate keratitis
• Xerostomia

Less Frequent

• Acute abdominal pain
• Arthralgia
• Arthritis
• Blepharoconjunctivitis
• Blurred vision
• Bronchitis
• Cataracts
• Conjunctival blanching
• Conjunctivitis
• Conjunctivitis
• Corneal staining
• Cough
• Dizziness
• Dry eye
• Dry eye
• Dysgeusia
• Dyspepsia
• Dyspnea
• Eye tearing
• Eyelid crusting
• Eyelid erythema
• Foreign body sensation of eye
• General weakness
• Hypercholesterolemia
• Hypotension
• Infection
• Insomnia
• Keratitis
• Muscle weakness
• Ocular discharge
• Ocular discharge
• Ocular hypertension
• Ocular pain
• Ocular redness
• Osteoporosis
• Palpitations
• Pharyngitis
• Photophobia
• Photophobia
• Sinusitis
• Skin rash
• Symptoms of anxiety
• Upper respiratory infection
• Visual field defect
• Vitreous floater

Rare or Very Rare

• Acute cognitive impairment
• Alopecia
• Angina
• Anorexia
• Behavioral disorders
• Blepharitis
• Blepharoptosis
• Blurred vision
• Chest pain
• Cough
• Delirium
• Depression
• Diarrhea
• Diplopia
• Dizziness
• Drowsy
• Dry eye
• Dry nose
• Dyspepsia
• Dyspnea
• Dysuria
• Erectile dysfunction
• Erythema
• Eye tearing
• Eyelid crusting
• Fatigue
• Foreign body sensation of eye
• General weakness
• General weakness
• Hallucinations
• Headache disorder
• Headache disorder
• Insomnia
• Iritis
• Libido changes
• Memory impairment
• Nasal congestion
• Nausea
• Nausea
• Nervousness
• Nightmares
• Ocular irritation
• Ocular redness
• Palpitations
• Paresthesia
• Pruritus of skin
• Psoriasiform eruption
• Raynaud's phenomenon
• Sensation of cold
• Skin pigmentation enhancement
• Skin rash
• Symptoms of anxiety
• Tinnitus
• Urticaria
• Vertigo
• Visual changes
• Vomiting
• Xerostomia
• Xerostomia

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Safety and efficacy of topical brimonidine tartrate for the treatment of open-angle glaucoma or ocular hypertension in pediatric patients younger than 2 years of age have not been established. Because potentially serious adverse effects, including apnea, bradycardia, coma, hypotension, hypothermia, hypotonia, lethargy, pallor, respiratory depression, and somnolence, have been reported in infants treated with topical brimonidine tartrate, use of the drug is contraindicated in infants younger than 2 years of age. In a well-controlled clinical study in children 2-7 years of age with glaucoma who received brimonidine tartrate 0.2% ophthalmic solution 3 times daily, the most commonly observed adverse effects were somnolence and decreased mental alertness; approximately 16% of these children discontinued therapy because of somnolence. The incidence of somnolence generally appeared to be age and weight related, occurring in 50-83% of children 2-6 years of age and 25% of those 7 years of age who weighed more than 20 kg.

The individual components of brinzolamide and brimonidine tartrate fixed-combination ophthalmic suspension have been studied in pediatric patients 4 weeks to 5 years of age (brinzolamide) and 2-7 years of age (brimonidine).

Safety and efficacy of brimonidine tartrate and timolol fixed-combination ophthalmic solution in pediatric patients 2-16 years of age have been established based on evidence from adequate and well-controlled studies of the fixed combination in adults and additional data from a study evaluating the individually administered drugs (brimonidine tartrate 0.2% administered 3 times daily as an adjunct to timolol therapy) in children 2-7 years of age with glaucoma.

Safety and efficacy of brimonidine tartrate 0.025% ophthalmic solution for self-medication for relief of ocular redness due to minor irritation have not been established in children younger than 5 years of age. Safety and efficacy in pediatric patients 5 years of age or older are supported by evidence from controlled clinical trials in adults and additional data from a safety study that included both adults and pediatric patients 5 years of age or older.

In studies in animals, brimonidine crossed the placenta and entered the fetal circulation to a limited extent; no evidence of teratogenicity was observed. There are no adequate and well-controlled studies of brimonidine to date in pregnant women. Brimonidine should be used during pregnancy only if potential benefits to the woman justify the potential risk to the fetus.

Reproduction studies in mice, rats, and rabbits using oral timolol dosages up to 50 mg/kg daily (7000 times the systemic exposure following the maximum recommended human ophthalmic dosage) have not revealed evidence of harm to the fetus. Although delayed fetal ossification was observed at this dosage in rats, no adverse effects on postnatal development occurred in this species. Oral timolol dosages of 1 g/kg daily (142,000 times the systemic exposure following the maximum recommended human ophthalmic dosage) were maternotoxic and resulted in an increased number of fetal resorptions in mice. Increased fetal resorptions were also observed in rabbits receiving oral timolol dosages 14,000 times the systemic exposure following the maximum recommended human ophthalmic dosage.

There are no adequate and controlled studies to date using timolol ophthalmic solution in pregnant women, and the drug should be used during pregnancy only when the potential benefits justify the possible risks to the fetus.

Reproduction studies in rabbits using oral dorzolamide at dosages that resulted in estimated peak plasma concentrations that were 37 times higher than the lower limit of detection in human plasma following ocular administration revealed malformations of the vertebral bodies. These malformations occurred at dosages that caused metabolic acidosis and decreased body weight gain in dams and decreased fetal weight. Reproductive studies in rabbits using oral dorzolamide at dosages that resulted in estimated peak plasma concentrations that were 15 times higher than the lower limit of detection in human plasma following ocular administration did not reveal evidence of teratogenic effects or embryotoxicity.

There are no adequate and controlled studies to date using dorzolamide in pregnant women, and the drug should be used during pregnancy only when the potential benefits justify the possible risks to the fetus.

Brimonidine is distributed into milk in animals. It is not known whether brimonidine is distributed into human milk following topical application to the eye. A decision should be made whether to discontinue nursing or the drug, taking into account the importance of the drug to the woman.

Timolol is distributed into milk following oral or topical ophthalmic administration. Because of the potential for serious adverse reactions from timolol in nursing infants, a decision should be made whether to discontinue nursing or the drug, taking into account the importance of the drug to the woman.

In lactating rats given oral dorzolamide at dosages that resulted in estimated peak plasma concentrations that were 52 times higher than the lower limit of detection in human plasma following ocular administration, decreases of 5-7% in body weight gain in offspring and developmental delay (i.e., incisor eruption, vaginal canalization, eye opening) secondary to lower fetal body weight have been reported.

It is not known whether dorzolamide is distributed into human milk. Because of the potential for serious adverse reactions to dorzolamide in nursing infants, a decision should be made whether to discontinue nursing or the drug, taking into account the importance of the drug to the woman.

No substantial differences in safety and efficacy have been observed between geriatric patients and younger adults.