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Clinical application of the inhibitory quotient: is there a role in HIV protease inhibitor therapy?

Winston, Alana; Khoo, Sayeb

Current Opinion in HIV and AIDS: November 2008 - Volume 3 - Issue 6 - p 608–611
doi: 10.1097/COH.0b013e328312972e
HIV protease inhibitors: Edited by Jon Schapiro and John Erickson

Purpose of review The inhibitory quotient of boosted protease inhibitors is a measurement incorporating both plasma drug exposure and resistance testing. Inhibitory quotients have been assessed in over 50 clinical studies to date, many of these studies describe highly significant associations between the inhibitory quotient and virological outcomes. This review will focus on studies that assess the inhibitory quotient in a prospective fashion and with the use of newly available boosted protease inhibitors.

Recent findings Atazanavir, darunavir and tipranavir are the three most recently licensed protease inhibitors. Studies have described associations between the inhibitory quotient and outcomes for all of these agents with cutoff inhibitory quotient values now proposed for all of these protease inhibitors.

A prospective study has assessed the use of inhibitory quotient across many different protease inhibitor regimens and although no overall benefit was described, improved clinical outcomes were observed in specific patient groups.

Summary Although ongoing challenges need to be overcome, recent studies have described associations between this useful parameter and modern day antiretroviral regimens.

aSection of Infectious Diseases, Division of Medicine, Imperial College, London, UK

bDepartment of Pharmacology, University of Liverpool, Liverpool, UK

Correspondence to Dr Alan Winston, Clinical Senior Lecturer and Consultant Physician, Clinical Trials, Ground Floor Winston Churchill Wing, Praed Street, Imperial College, St. Mary's Campus, London W2 1NY, UK Tel: +44 207 886 7718; fax: +44 207 886 6123; e-mail:

© 2008 Lippincott Williams & Wilkins, Inc.