pH and the potential irritancy of douche formulations to the vaginal mucosa of the albino rabbit and rat.

Studies were conducted to determine the effect of the pH of a vagina douche on its irritation potential for the vaginal mucosa of the albino rabbit and albino rat. The pH of a liquid douche formulation was varied by modification of the lactic acid/sodium bicarbonate ratio and the resulting preparations were administered intravaginally by lavage once a day for four consecutive days. On day 5, the animals were killed and the vaginal tissues were processed and examined histopathologically. Using a predetermined semiquantitative scoring system, it was not in the rat. As the pH was decreased, the degree of irritation became more severe in the rabbit; at pH 3.0 and below, irritation was sufficiently severe for the formulation to be considered unacceptable for human use. Only minimal irritation was seen in the rat at any of the pH levels dependent below 3 . 0. This exaggerated response must be taken into consideration when the rabbit is used for assessing the vaginal-irritation potential of douches. The rabbit, having a vaginal mucosa more sensitive than that of the rat, remains an appropriate model for measuring the potential irritancy of new douche products, because comparisons can be made with products of known irritancy.