Vaginal prophylactic methodology may prevent heterosexual transmission of the HIV
and other sexually transmitted disease-causing organisms as well as unplanned pregnancies.
A new delivery system (ACIDFORM) was designed with acid-buffering, bioadhesive, and
viscosity-retaining properties to (1) maintain the acidic vaginal milieu (the low
pH inactivates many pathogens and spermatozoa), (2) form a protective layer over the
vaginal/cervical epithelium (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 detail, ACIDFORM's acid-buffering,
bioadhesive, viscosity-retaining, and spermicidal 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.
ACIDFORM adheres well to two model membranes (excised sheep vagina and cellophane)
and is more bioadhesive than Conceptrol, Advantage S, Replens, Aci-Jel, and 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 an active ingredient with antimicrobial and/or contraceptive