Ritonavir-dependent fluconazole boosting of nelfinavir: a report of three cases

Sir, The use of ritonavir-boosted dual protease inhibitor (PI) combinations is increasingly considered in HIV-infected patients with a history of multiple therapeutic failures. 1 Although phar- macokinetic (PK) studies on several of such combinations pro- vided valuable information on how to cope with drug-drug interactions between concurrently administered PIs, substantial uncertainty persists on the best management of double-boosted PI-based regimens. 2 In this setting, the introduction of fluc- onazole as additional boosting agent was found to restore the otherwise reciprocally reduced concentrations of co- administered lopinavir/ritonavir and amprenavir, and higher PI PK exposure was also documented when fluconazole was added to ritonavir/saquinavir and ritonavir/tipranavir. 3-5 In a