To objectively evaluate the performance of new vaginal dosage forms, it is important to determine their time of residence and their distribution. This paper describes the in vivo characteristics of a reference and test product in this situation.
Method: A randomised cross-over study was performed in the same phase of the menstrual cycle in eight pre-menopausal women. The retention and distribution of a commercially available vaginal clotrimazole cream and a test gel product, each "labelled" with 99mTc-DTPA was assessed by gamma scintigraphy for 24 h after administration of the products. Mass balance analysis was attempted by collecting and counting sanitary napkins worn for the study time.
Results: Within individuals there was little variation in the clearance of the formulations, but wide variation between individuals with a range between 81 and 1% of the administered doses retained by 24 h. The losses appeared to occur mainly at times of urination with 12 +/- 8% (cream) and 20 +/- 23% (gel) collected on the sanitary napkins, but 46 +/- 34% (cream) and 38 +/- 22% gel activity not accounted for by 24 h. The intravaginal distribution of activity was similar for each product.
Conclusions: Radioactive tracer methods are useful in assessing and comparing vaginal dosage forms.