Quantitative Imaging and Sigmoidoscopy to Assess Distribution of Rectal Microbicide Surrogates

Understanding the distribution of microbicide and human immunodeficiency virus (HIV) within the gastrointestinal tract is critical to development of rectal HIV microbicides. A hydroxyethylcellulose‐based microbicide surrogate or viscosity‐matched semen surrogate, labeled with gadolinium‐DTPA (diethylene triamine pentaacetic acid) and 99mTechnetium‐sulfur colloid, was administered to three subjects under varying experimental conditions to evaluate effects of enema, coital simulation, and microbicide or semen simulant over 5 h duration. Quantitative assessment used single photon emission computed tomography (SPECT)/computed tomography (CT) and magnetic resonance imaging (MRI) imaging, and sigmoidoscopic sampling. Over 4 h, radiolabel migrated cephalad in all studies by a median (interquartile range) of 50% (29–102%; P