ABSTRACT
Standard pharmacokinetic practice is to first do a single-dose application to determine bioavailability. This standard application is no different for percutaneous absorption and most absorption values are for single doses. But think of topical application (or any drug dosing) and the procedure is repeated, whether once per day for several days (or longer) or multiple times during the day, which also can go on for several days (or longer). There are few one-dose magic bullets in pharmaceutics. Therefore, it becomes important to view multiple topical dosing, especially if that is the standard procedure with which a topical drug is used, or if such exposure occurs for a hazardous environmental chemical.
