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Lower Dose of Ritonavir Approved for Use with Fosamprenavir

The FDA recently approved a new dosing strategy for use in treatment-naive patients: 1400 mg of fosamprenavir with 100 mg of ritonavir, both taken once daily.

On October 12, 2007, the FDA approved a new dose of ritonavir (100 mg once daily) for boosting fosamprenavir (1400 mg once daily) in treatment-naive HIV-infected patients. Approval was based on data from an industry-sponsored pharmacokinetic study, in which investigators compared the new 100-mg once-daily dose of ritonavir with a previously approved dose (200 mg once daily) in 36 healthy volunteers who also received once-daily fosamprenavir. Plasma levels of fosamprenavir were comparable with the two ritonavir doses after 14 days, but the lower dose of ritonavir was associated with fewer adverse events and smaller mean increases in triglyceride levels (Antimicrob Agents Chemother 2007; 51:560). Two pilot studies of this dosing strategy in treatment-naive patients have already been presented (ACC Oct 30 2006 and Abstract P2, 8th International Congress on Drug Therapy in HIV Infection, 2006), and a clinical trial is underway.

With the approval of this new strategy, fosamprenavir can now be administered to treatment-naive patients in any of the following dosages:

• 1400 mg of fosamprenavir twice daily (with no boosting)
  
• 1400 mg of fosamprenavir once daily plus 100 mg of ritonavir once daily
  
• 1400 mg of fosamprenavir once daily plus 200 mg of ritonavir once daily
  
• 700 mg of fosamprenavir twice daily plus 100 mg of ritonavir twice daily
  

— Paul E. Sax, MD

Published in Journal Watch HIV/AIDS Clinical Care October 22, 2007

Citation(s):

Lexiva (fosamprenavir calcium) tablets and oral suspension [prescribing information]. Research Triangle Park, NC: GlaxoSmithKline, Inc; 2007. (http://us.gsk.com/products/assets/us_lexiva.pdf)

FDA approves administration of LEXIVA® with lower dose of "boosting" medication ritonavir [press release]. Research Triangle Park, NC: GlaxoSmithKline, Inc; October 12 , 2007. (http://us.gsk.com/ControllerServlet?appId=4&pageId=402&newsid=1158)

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