See the DrugPatentWatch profile for rifampin
Rifampin does not appear to affect the efficacy of famciclovir based on available information.
Can rifampin interact with famciclovir?
Drug interaction studies and prescribing information for famciclovir do not indicate a significant pharmacokinetic or pharmacodynamic interaction between famciclovir and rifampin. Famciclovir is a prodrug that is converted to its active form, penciclovir, in the body. Penciclovir is primarily eliminated unchanged in the urine [1]. Rifampin is a potent inducer of cytochrome P450 enzymes, which can affect the metabolism of many drugs. However, famciclovir is not a significant substrate for these enzymes, suggesting it is less likely to be affected by rifampin's induction properties [2].
How is famciclovir metabolized?
After oral administration, famciclovir is rapidly converted to penciclovir. Penciclovir is the active antiviral moiety. The elimination half-life of penciclovir is approximately 2 hours in individuals with normal renal function. Renal impairment can significantly prolong the half-life of penciclovir [1].
What is rifampin's mechanism of action?
Rifampin is a broad-spectrum antibiotic used to treat various bacterial infections, including tuberculosis. It works by inhibiting bacterial DNA-dependent RNA polymerase, thereby blocking RNA synthesis [3].
What is famciclovir used for?
Famciclovir is an antiviral medication used to treat infections caused by herpes simplex virus and varicella zoster virus, such as herpes zoster (shingles), genital herpes, and cold sores [1].
Sources
1. https://www.ncbi.nlm.nih.gov/books/NBK547788/
2. https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/050728s024,050729s021,050730s020lbl.pdf
3. https://www.ncbi.nlm.nih.gov/books/NBK538184/