RIMANTADINE HYDROCHLORIDE
Clinical safety rating: safe
Animal studies have demonstrated safety
Rimantadine is a tricyclic amine antiviral that inhibits influenza A virus replication by blocking the M2 proton ion channel, preventing viral uncoating and release of viral RNA into host cells.
| Metabolism | Hepatic primarily via cytochrome P450 (CYP) enzymes, mainly CYP3A4, with renal excretion of unchanged drug and metabolites. |
| Excretion | Renal: 75% unchanged; fecal: <10%; biliary: minimal. Total clearance 2.5 mL/min/kg. |
| Half-life | 25.4 hours (range 13–65 h); prolonged in elderly (38 h) and severe renal impairment (CrCl <10 mL/min: up to 130 h). |
| Protein binding | 40% bound to alpha-1-acid glycoprotein and albumin. |
| Volume of Distribution | 17 L/kg; extensive tissue distribution, high lung concentrations (10-fold plasma). |
| Bioavailability | Oral: 75–95%; no intravenous formulation available. |
| Onset of Action | Oral: ~2–4 days for clinical response (influenza A prophylaxis/treatment). |
| Duration of Action | 14 days (prophylaxis); treatment duration 5–7 days. Once-daily dosing maintains therapeutic levels. |
100 mg orally twice daily for 7 days; initiate within 48 hours of symptom onset.
| Dosage form | TABLET |
| Renal impairment | CrCl 30-50 mL/min: 100 mg orally once daily; CrCl <30 mL/min or hemodialysis: 100 mg orally every 48 hours. |
| Liver impairment | Child-Pugh Class A: no adjustment; Child-Pugh Class B: 100 mg orally once daily; Child-Pugh Class C: 100 mg orally every 48 hours. |
| Pediatric use | Children ≥10 years: 5 mg/kg/day orally in 2 divided doses, max 150 mg/day; children <10 years: 5 mg/kg/day orally in 2 divided doses, max 150 mg/day. |
| Geriatric use | Patients ≥65 years: 100 mg orally once daily due to age-related decline in renal function; monitor for CNS effects. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Acetaminophen and aspirin may decrease rimantadine levels Can cause CNS side effects like insomnia and dizziness.
| Breastfeeding | Not known if excreted in human breast milk; M/P ratio not determined. Due to potential for serious adverse reactions, a decision should be made to discontinue nursing or discontinue drug, taking into account importance of drug to mother. |
| Teratogenic Risk | Adequate studies in pregnant women are not available. Rimantadine is embryotoxic and teratogenic in animal studies at doses 3x the human recommended dose. Use only if potential benefit justifies potential risk. First trimester: avoid unless essential. Second and third trimesters: limited data, weigh risks. |
■ FDA Black Box Warning
None
| Common Effects | Insomnia |
| Serious Effects |
["Hypersensitivity to rimantadine or any component of the formulation","History of seizures or epilepsy (relative contraindication due to CNS stimulation)"]
| Precautions | ["Use with caution in patients with hepatic impairment, renal impairment, seizure disorders, or elderly patients due to increased risk of central nervous system effects.","May cause CNS side effects such as nervousness, anxiety, insomnia, and difficulty concentrating. Caution in activities requiring alertness.","Resistance can develop during treatment; not effective against influenza B.","Reduce dose in severe hepatic impairment or severe renal impairment (CrCl < 50 mL/min)."] |
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| Fetal Monitoring | Monitor maternal renal and hepatic function. Monitor for CNS effects (insomnia, dizziness, headache) and gastrointestinal intolerance. Fetal monitoring: ultrasound for growth and development if exposed during first trimester. |
| Fertility Effects | No human data on fertility. In animal studies, rimantadine did not impair fertility at doses up to 3x human dose. Effects on reproductive function are unknown. |