effects of gel volume on pharmacokinetics for vaginal and rectal applications of combination duogeliqb4012 a dual chamberdual drug hiv microbicide gel in pigtailed macaques this study evaluated effects of differing gel volumes on pharmacokinetics pk iqb4012 a gel containing the nonnucleoside reverse transcriptase inhibitor iqp0528 and tenofovir tfv was applied to the pigtailed macaque vagina and rectum vaginal gel volumes 1 loading of both drugs were 05 or 15 ml following washout 1 or 4 ml of gel were then applied rectally blood vaginal and rectal fluids were collected at 0 2 4 and 24 h vaginal and rectal tissue biopsies were collected at 4 and 24 h there were no statistically significant differences in concentrations for either drug between gel volumes within compartments at matched time points after vaginal gel application median iqp0528 concentrations were 104105 ngg 105106 ngml and 103105 ngml in vaginal tissues vaginal fluids and rectal fluids respectively over 24 h median vaginal tfv concentrations were 12 logs lower than iqp0528 levels at matched time points after rectal gel application median iqp0528 and tfv concentrations in rectal fluids were 103105 ngml and 102103 ngml respectively concentrations of both drugs sampled in rectal tissues were low 101103 ngg for 1 ml gel half of sampled rectal tissues had undetectable concentrations of either drug and over half of sampled rectal fluids had undetectable tfv concentrations these results indicate differences in drug delivery between the vaginal and rectal compartments and that smaller vaginal gel volumes may not significantly compromise microbicide pk and prophylactic potential however effects of rectal gel volume on pk for both drugs were less definitive