Intravaginal rings: controlled release systems for contraception and prevention of transmission of sexually transmitted infections.

Intravaginal rings (IVRs) are a dosage form used to locally or systemically deliver drugs in the vagina. They are capable of releasing one or more drugs over an extended period of time (from several weeks to a year or longer). Contraceptive IVRs are currently gaining popularity due to the success of the contraceptive product NuvaRing®. Delivery of contraceptives from IVRs should promote compliance/adherence, and they also provide effective cycle control and symptom relief (menorrhagia, dysmenorrheal, and polycystic ovarian syndrome). Vaginal delivery of proteins from IVRs was first explored in an attempt to deliver IgG2a antibody intravaginally to neutralize herpes simplex virus 2. More recently, IVRs capable of releasing antibodies and recombinant proteins potentially along with low molecular weight microbicides are under investigation for prevention of HIV-1 transmission. Vaginal delivery of microbicides has been studied with several drugs most notably the non-nucleoside reverse transcriptase inhibitor dapivirine. Another drug capable of blocking transmission of HIV-1 when released from IVRs is tenofovir. Finally, combinations of drugs with different indications (i.e., multipurpose prevention technologies) are actively being pursued.