Vaginal pharmaceutical compositions are described. These compositions contain (i) an active pharmaceutical ingredient selected from the group consisting of antimicrobial imidazoles and mixtures thereof, and (ii) a polysaccharide, wherein the pH of the composition is greater than 4.25 and less than about 8. In particularly preferred compositions, the active pharmaceutical ingredient includes metronidazole and the polysaccharide includes hypromellose. These compositions can be applied to vaginal tissue for treatment of various diseases, such as bacterial vaginosis, or for prophylaxis.