Procedure for the evaluation of the bioavailability of topical formulations in vivo as the rate and extent to which the active drug product is transferred from the vehicle to the skin

✍ Scribed by Josep Vergés; Gilberto Castañeda-Hernández; José M. Moragas

• Publisher: John Wiley and Sons
• Year: 1995
• Tongue: English
• Weight: 578 KB
• Volume: 36
• Category: Article
• ISSN: 0272-4391
• DOI: 10.1002/ddr.430360404

✦ Synopsis

A procedure was developed for the in vivo evaluation of the bioavailability of topical formulations containing a limited amount of the active drug product estimated as the rate and extent to which the drug i s released from the vehicle to the skin. It i s assumed that drug transfer follows Fick's law of diffusion. The formulation tested was a cream containing 40 pmol/ml (20 mgiml) of sertaconazole, a novel imidazole antifungal agent, applied to healthy volunteers. Eight 9 cm2 squares were marked in the volar forearm surface and 0.1 ml of the cream was applied to each square by gentle rubbing with a plastic thimble. The actually applied dose was estimated considering the drug amount that adhered to the thimble. Then one area at a time was cleansed at 0, 1, 2, 4, 6 , 8, 12, and 24 h and the amount of sertaconazole transferred to the skin was estimated by determination of the amount of drug removed by cleansing. Drug release from the vehicle to the skin increased with time, but then reached a plateau. The maximal amount of drug transferred to the skin was 85.5 ? 3.3% (mean i-S.D.) of the actually applied dose, and this value was considered an expression of the extent of drug release. The rate of release was estimated as the half-life of the transfer process, which was 1.83 ? 0.76 h. This procedure is suitable for the evaluation of topical formulations containing a limited amount of the active drug product.