Properties of a new acid-buffering bioadhesive vaginal formulation (ACIDFORM)

Vaginal prophylactic methodology may prevent heterosexual transmission of t he HIV and other sexually transmitted disease-causing organisms as well as unplanned pregnancies. A new delivery system (ACIDFORM) was designed with a cid-buffering, bioadhesive, and viscosity-retaining properties to (1) maint ain the acidic vaginal milieu (the low pH inactivates many pathogens and sp ermatozoa), (2) form a protective layer over the vaginal/cervical epitheliu m (minimizing contact with pathogenic organisms), and (3) provide long-term vaginal retention. A Phase I clinical study with ACIDFORM provided initial information about its safety and showed the formation of a layer over the vaginal/cervical epithelium [1; Amaral et al., Contraception 1999;60:361-6] . To study the properties of the gel (without active ingredient) in more de tail, ACIDFORM's acid-buffering, bioadhesive, viscosity-retaining, and sper micidal properties were compared in vitro to marketed formulations, and its long-term stability was assessed. ACIDFORM, either when titrated with NaOH or when mixed directly with semen, is highly acid buffering and much more effective than Aci-Jel, a commercial acid-buffering vaginal product. ACIDFO RM adheres well to two model membranes (excised sheep vagina and cellophane ) and is more bioadhesive than Conceptrol, Advantage S, Replens, Aci-Jel, a nd K-Y jelly. On dilution, ACIDFORM also retains its viscosity better than these marketed products. ACIDFORM is spermicidal and is stable for at least 2 years. These results suggest that ACIDFORM has advantages over presently marketed vaginal delivery systems. The gel may either be useful by itself as an antimicrobial contraceptive product or as a formulation vehicle for a n active ingredient with antimicrobial and/or contraceptive properties. (C) 2001 Elsevier Science Inc. All rights reserved.