Fosfomycin Tromethamine (fosfomycin tromethamine)

Dosage of fosfomycin tromethamine is expressed in terms of fosfomycin.

Fosfomycin tromethamine is administered orally. Although fosfomycin has been administered IV+ as the disodium salt, a parenteral formulation of the drug is not commercially available in the US.

Fosfomycin tromethamine for oral administration is available as granules for oral solution that must be dissolved in water prior to administration. The drug should not be ingested as dry granules.

The oral solution should be prepared by pouring the entire contents of a single-dose packet (sachet) containing 3 g of fosfomycin into 90-120 mL (3-4 ounces) of water and stirring until the granules dissolve. The entire oral solution should be ingested immediately after preparation. Hot water should not be used to dissolve fosfomycin tromethamine granules.

Although food decreases oral bioavailability of fosfomycin tromethamine, the manufacturer states that the drug may be administered without regard to food since the cumulative amount of fosfomycin excreted in urine is similar whether the drug is given with or without food. (See Pharmacokinetics.)

There is no enhanced messaging for this drug.

Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

Antibiotics/Fecal Microbiota

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Fecal microbiota is a suspension of live bacteria, which may be compromised by concurrent use of antibiotics.(1)

CLINICAL EFFECTS: Antibiotics may decrease the effectiveness of fecal microbiota.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Antibiotics should not be used concurrently with fecal microbiota. Antibacterial treatment should be completed for 24 to 72 hours before initiating treatment with fecal microbiota. Do not use antibiotics for up to 8 weeks after fecal microbiota.(1)

DISCUSSION: Antibiotics may compromise the effectiveness of fecal microbiota.

Antibiotics/Fecal Microbiota Spores

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Fecal microbiota spores is a suspension of live bacterial spores, which may be compromised by concurrent use of antibiotics.(1)

CLINICAL EFFECTS: Antibiotics may decrease the effectiveness of fecal microbiota spores.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Antibiotics should not be used concurrently with fecal microbiota spores. Antibacterial treatment should be completed for 2 to 4 days before initiating treatment with fecal microbiota spores.(1)

DISCUSSION: Antibiotics may compromise the effectiveness of fecal microbiota spores.

Antimicrobials/Live Typhoid Vaccine

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: The antimicrobial may be active against the organism in the live-vaccine. Antimicrobial therapy may prevent the vaccine organism from replicating enough to trigger an immune response.(1)

CLINICAL EFFECTS: Vaccination may be ineffective.

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Do not give oral typhoid vaccine until 72 hours after the last dose of antimicrobial. If possible, to optimize vaccine effectiveness, do not start antibacterial drugs for 72 hours after the last dose of oral typhoid vaccine. A longer interval should be considered for long-acting antimicrobials, such as azithromycin.(3)

DISCUSSION: Because antimicrobial therapy may prevent sufficient vaccine-organism replication to generate an immune response, the manufacturer of live-attenuated typhoid vaccine and the Centers for Disease Control (CDC) state that the vaccine should not be administered to patients receiving antimicrobial therapy.(1-3)

Fosfomycin, Oral/Metoclopramide

SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

MECHANISM OF ACTION: Metoclopramide may decrease the amount of fosfomycin absorbed.(1)

CLINICAL EFFECTS: The concurrent use of metoclopramide may result in reduced levels of fosfomycin and treatment failure.(1)

PREDISPOSING FACTORS: None determined.

PATIENT MANAGEMENT: Fosfomycin should not be used in patients receiving metoclopramide.(1) Consider the use of alternative urinary tract anti-infectives in patients maintained on metoclopramide. If concurrent use is warranted, monitor patients for fosfomycin treatment failure.

DISCUSSION: Metoclopramide has been shown to reduce fosfomycin levels. Urinary levels of fosfomycin may not exceed required bactericidal levels for a long enough period of time to result in microbiological cure.(1)

There are no severe interactions for this drug.

There are no moderate interactions for this drug.

Fosfomycin tromethamine is contraindicated in patients with known hypersensitivity to the drug.

There are no contraindication contraindications for this drug.

• Clostridioides difficile infection

• Kidney disease with reduction in glomerular filtration rate (GFr)

Adverse effects reported in more than 1% of patients receiving oral fosfomycin in clinical studies include adverse GI effects (diarrhea, nausea, dyspepsia), headache, dizziness, asthenia, and vaginitis.

More Frequent

• Vaginitis

Rare or Very Rare

• Clostridioides difficile infection

More Frequent

• Diarrhea
• Headache disorder
• Nausea

Less Frequent

• Abdominal pain with cramps
• Back pain
• Dizziness
• Dysmenorrhea
• Dyspepsia
• General weakness
• Pain
• Pharyngitis
• Rhinitis
• Skin rash

No enhanced messaging available.

Safety and efficacy of fosfomycin have not been established in children 12 years of age or younger.

There are no adequate and well-controlled studies using fosfomycin in pregnant women. Fosfomycin should be used during pregnancy only if clearly needed.

It is not known whether fosfomycin is distributed into milk.

Because of the potential for serious adverse reactions in nursing infants, a decision should be made to discontinue nursing or not administer fosfomycin, taking into account the importance of the drug to the woman.

Dosage adjustments are not usually necessary in geriatric patients; however, dosage should be selected with caution because of the greater frequency of decreased hepatic, renal, and/or cardiac function and of concomitant disease and drug therapy. (See Geriatric Use under Warnings/Precautions: Specific Populations, in Cautions.)

Clinical studies of fosfomycin did not include sufficient numbers of patients 65 years of age or older to determine whether geriatric patients respond differently than younger patients. Although other clinical experience has not identified age-related differences in response or tolerance, dosage for geriatric patients should be selected with caution and the greater frequency of decreased hepatic, renal, or cardiac function and of concomitant disease or other drug therapy in this age group should be considered.