In vivo skin penetration studies may be undertaken for one or more of the following purposes:

1 To verify and quantify the cutaneous BIOAVAILABILITY of a topically applied drug. 2 To verify and quantify the systemic BIOAVAILABILITY of a transdermal drug. 3) To establish BIOEQUIVALENCE of different topical formulations of the same drug substance. 4) To determine the incidence and degree of systemic TOXICOLOGIC RISK following topical application of a specific drug or drug product. 5) To relate resultant blood levels of drug in human to systemic therapeutic effects.