Tuesday, April 19, 2011 1:08:32 AM
Small print at the end:
Viagra (sildenafil) doses must be low when the drug is used with HIV protease inhibitors (especially ritonavir), because these antiretrovirals reduce the metabolism of sildenafil in the liver, resulting in abnormally high blood levels which can cause adverse effects. The combination does not seem to affect blood levels of protease inhibitors.
Sildenafil, used to treat erectile dysfunction, is supplied as tablets in three doses: 25, 50, and 100 mg, and is taken 1/2 an hour to 4 hours before intercourse. Doctors often start with 50 mg, then lower or raise the dose if needed. According to an April 21 "Backgrounder for HIV Treatment Advocates" from Pfizer Inc., "Given the magnitude of the interaction between sildenafil and protease inhibitors, ongoing discussions with the FDA indicate that a maximum single dose of 25 mg of sildenafil in a 48 hour period should not be exceeded in patients receiving these agents concurrently."