Methods and compositions are provided for reducing transmission and/or infection of HIV in a subject by increasing the bioavailability of a drug in the subject. The methods and compositions provided herein include an efflux transporter inhibitor and a drug effective for reducing the transmission and/or infection of HIV in a subject. The efflux transporter inhibitor is effective to reduce the efflux of the drug through at least one of P-glycoprotein (Pgp), breast cancer resistant protein (BCRP), and multidrug resistant associated protein 1-9 (MRP1-9).