Dose Response for Starting and Stopping HIV Preexposure Prophylaxis for Men Who Have Sex With Men

Background. This study estimated the number of daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) doses required to achieve and maintain (after discontinuation) intracellular drug concentrations that protect against human immunodeficiency virus (HIV) infection for men who have sex with men (MSM). Methods. Tenofovir diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells (PBMCs) and rectal mononuclear cells from an intensive pharmacokinetic study ("Cell-PrEP" [ preexposure prophylaxis]) of 30 days of daily TDF/FTC followed by 30 days off drug were evaluated. A regression formula for HIV risk reduction derived from PBMCs collected in the preexposure prophylaxis initiative study was used to calculate inferred risk reduction. The time required to reach steady state for TFV-DP in rectal mononuclear cells was also determined. Results. Twenty-one HIV-uninfected adults participated in Cell-PrEP. The inferred HIV risk reduction, based on PBMC TFV-DP concentration, reached 99% (95% confidence interval [CI], 69%-100%) after 5 daily doses, and remained >90% for 7 days after stopping drug from steady-state conditions. The proportion of participants reaching the 90% effective concentration (EC 90 ) was 77% after 5 doses and 89% after 7 doses. The percentage of steady state for natural log [TFV-DP] in rectal mononuclear cells was 88% (95% CI, 66%-94%) after 5 doses and 94% (95% CI, 78%-98%) after 7 doses. Conclusions. High PrEP activity for MSM was achieved by approximately 1 week of daily dosing. Although effective intracellular drug concentrations persist for several days after stopping PrEP, a reasonable recommendation is to continue PrEP dosing for 4 weeks after the last potential HIV exposure, similar to recommendations for postexposure prophylaxis

Effect of Antacids on the Pharmacokinetics of Raltegravir in Human Immunodeficiency Virus-Seronegative Volunteers▿

Raltegravir's divalent metal ion chelating motif may predispose the drug to interactions with divalent cations. We determined whether a divalent cation-containing antacid interacted with raltegravir. Twelve HIV-1-seronegative subjects were enrolled in this randomized, prospective, crossover study of single-dose raltegravir (400 mg) with and without an antacid. Subjects underwent two intensive pharmacokinetic visits in the fasted state separated by a 5- to 12-day washout period. With simultaneous antacid administration, time to peak raltegravir concentration occurred 2 h sooner (P = 0.002) and there was a 67% lower raltegravir concentration at 12 h postdose (P < 0.0001) than with administration of raltegravir alone. The raltegravir area under the-concentration-time curve from 0 to 12 h and maximum concentration were unchanged with the addition of an antacid. Studies are needed to determine the clinical relevance of this interaction, whether it remains after multiple dosing to steady state, whether it is mitigated by temporal separation, and whether raltegravir interacts with divalent cation-containing vitamins, supplements, or foods

Dose Response for Starting and Stopping HIV Preexposure Prophylaxis for Men Who Have Sex With Men

BackgroundThis study estimated the number of daily tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) doses required to achieve and maintain (after discontinuation) intracellular drug concentrations that protect against human immunodeficiency virus (HIV) infection for men who have sex with men (MSM).MethodsTenofovir diphosphate (TFV-DP) concentrations in peripheral blood mononuclear cells (PBMCs) and rectal mononuclear cells from an intensive pharmacokinetic study ("Cell-PrEP" [preexposure prophylaxis]) of 30 days of daily TDF/FTC followed by 30 days off drug were evaluated. A regression formula for HIV risk reduction derived from PBMCs collected in the preexposure prophylaxis initiative study was used to calculate inferred risk reduction. The time required to reach steady state for TFV-DP in rectal mononuclear cells was also determined.ResultsTwenty-one HIV-uninfected adults participated in Cell-PrEP. The inferred HIV risk reduction, based on PBMC TFV-DP concentration, reached 99% (95% confidence interval [CI], 69%-100%) after 5 daily doses, and remained &gt;90% for 7 days after stopping drug from steady-state conditions. The proportion of participants reaching the 90% effective concentration (EC90) was 77% after 5 doses and 89% after 7 doses. The percentage of steady state for natural log [TFV-DP] in rectal mononuclear cells was 88% (95% CI, 66%-94%) after 5 doses and 94% (95% CI, 78%-98%) after 7 doses.ConclusionsHigh PrEP activity for MSM was achieved by approximately 1 week of daily dosing. Although effective intracellular drug concentrations persist for several days after stopping PrEP, a reasonable recommendation is to continue PrEP dosing for 4 weeks after the last potential HIV exposure, similar to recommendations for postexposure prophylaxis