Benadryl Allergy Plus Congest (phenylephrine HCl/diphenhydramine HCl)

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Last reviewed · Source: First Databank (FDB) drug data

Overview

Phenylephrine hydrochloride is an alpha1-adrenergic receptor agonist.

Diphenhydramine is an ethanolamine-derivative, first generation antihistamine.

The phenylephrine activation of alpha1-adrenergic receptors on vascular smooth muscle cells results in vasoconstriction. Following IV administration of phenylephrine hydrochloride, systolic and diastolic blood pressure, mean arterial blood pressure, and total peripheral vascular resistance are increased. Vasoconstriction occurs in most vascular beds, including renal, pulmonary, and splanchnic arteries, but minimal to no effect is observed on cerebral blood vessels.

Hepatic vascular beds are also affected. In some patients, phenylephrine can substantially reduce cardiac output, presumably due to increased afterload; however, the exact effects of the drug on global cardiac output depend on the dose and contributory effects of the arterial and venous vasculature. Although phenylephrine reduces venous compliance and can potentially increase venous return, accompanying increases in arterial and venous resistance can negate this potential benefit.

With increased blood pressure following IV administration, there is increased vagal activity, resulting in reflex bradycardia. Phenylephrine constricts both arterial and venous blood vessels, although its effects on arterial vessels are more pronounced. At clinically relevant dosages, phenylephrine increases myocardial work and oxygen requirements.

Following an IV bolus of phenylephrine hydrochloride, blood pressure increase is rapid, typically occurring within minutes. Blood pressure effects from a phenylephrine bolus may persist for up to 20 minutes. Phenylephrine is widely distributed into organs and peripheral tissues.

It is not known if phenylephrine or its metabolite are distributed into human or animal milk following parenteral administration.

Phenylephrine is extensively metabolized in the liver. Phenylephrine primarily undergoes metabolism by sulfotransferase and monoamine oxidase (MAO) to pharmacologically inactive metabolites. The 2 major metabolites are m-hydroxymandelic acid and sulfate conjugates.

Following IV administration of phenylephrine, approximately 86% of the dose is excreted in urine within 48 hours, principally as metabolites; approximately 16% of the dose is excreted in urine as unchanged drug. The terminal elimination half-life of phenylephrine averages 2.5 hours following IV administration. The observed effective half-life is approximately 5 minutes following IV infusion of the drug.

Patients with hepatic cirrhosis may have a reduced response to phenylephrine, potentially requiring higher dosages of the drug. Patients with end-stage renal disease may have an increased response to phenylephrine, potentially requiring lower dosages of the drug.

Diphenhydramine shares the actions and uses of other antihistamines.

Generic name: phenylephrine HCl/diphenhydramine HCl

Reference product & biosimilars

No reference, biosimilar or interchangeable associated with this drug.

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Indications

The following indications are listed for Benadryl Allergy Plus Congest:

  • Allergic Conjunctivitis
  • Allergic Rhinitis
  • Cold Symptoms
  • Nasal Congestion
  • Perennial Allergic Rhinitis
  • Rhinorrhea
  • Seasonal Allergic Rhinitis
  • Sneezing
  • Vasomotor Rhinitis

Also known as: Allergy Eye Itch, Atopic Conjunctivitis, Atopic Rhinitis, Intermittent Allergic Rhinitis, Itchy Eyes Due To Allergies, Nasal Stuffiness, Non-Seasonal Allergic Rhinitis, Ocular Itching Due To Allergies, Periodic Runny Nose, Seasonal Allergy.

Dosing

Dosage should be individualized according to the patient's response and tolerance.

Drug interactions

There is no enhanced messaging for this drug.

Contraindications

*Known hypersensitivity to phenylephrine or to any ingredient in the respective formulation.

Adverse reactions

The most commonly reported adverse effects in patients receiving IV phenylephrine hydrochloride were nausea, vomiting, and headache.

Precautions

No enhanced messaging available.

ICD codes

No ICD codes are available for this drug.

Formulary status

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Last reviewed · Source: First Databank (FDB) drug data