Famciclovir
Generic Details
Generic Name
Famciclovir
Other Names
- Famvir
Drug Class
- Antiviral
Chemical Formula
C14H19N5O4
Molecular Weight
321.33 g/mol
Mechanism of Action
- Famciclovir is a prodrug that is converted to penciclovir, which inhibits viral DNA synthesis by competing with deoxyguanosine triphosphate for viral DNA polymerase.
Indications
- Herpes zoster (shingles)
- Genital herpes
Common Dosage Forms
- Tablet
Typical Dosage
- Herpes zoster: 500 mg every 8 hours for 7 days
- Genital herpes: Initial episode 250 mg every 8 hours for 7-10 days
Pediatric Dosage
- Safety and efficacy not established in children
Geriatric Dosage
- Dose adjustment may be necessary in elderly patients with renal impairment
Side Effects
- Headache
- Nausea
- Diarrhea
- Fatigue
- Dizziness
Contraindications
- Hypersensitivity to famciclovir or penciclovir
Pregnancy Category
- Category B - Animal reproduction studies have failed to demonstrate a risk to the fetus and there are no adequate and well-controlled studies in pregnant women.
Lactation Safety
- Use caution when breastfeeding as it is unknown whether famciclovir is excreted in human milk.
Drug Interactions
- Probenecid may increase and prolong the serum concentrations of penciclovir
- Concomitant use with nephrotoxic drugs may increase the risk of renal toxicity
Overdose Symptoms
- Confusion
- Hallucinations
- Agitation
Antidote for Overdose
- There is no specific antidote, treatment is supportive
Storage Conditions
- Store at room temperature away from moisture and heat
Pharmacokinetics
- Absorption: Rapidly converted to penciclovir
- Distribution: Distributed widely in body tissues
- Metabolism: Converted to penciclovir by first-pass metabolism in the liver
- Excretion: Excreted mainly in urine
Precautions
- Renal impairment
- Hepatic impairment
Warnings
- May cause dizziness or confusion, use caution when driving or operating machinery