Drug Parameters Important for Transdermal Delivery.
Transdermal Delivery of Drugs, 1987 Apr; III:3-22
Parameters important for determining the feasibility of administering drugs transdermally were reviewed. Three criteria were considered important for determining whether a drug can be administered transdermally to achieve systemic pharmacological effects: biological, physiochemical, and pharmacokinetic. Biological criteria appropriate for transdermal delivery included the drug having a favorable therapeutic index after passing through the stratum corneum, the ability to avoid being inactivated, and having a short biological halflife. Certain factors can limit transdermal delivery. The drug must not induce a cutaneous irritant or allergic response. The pharmacological activity of the drug must be suitable for transdermal delivery, that is, one must ensure that tolerance to the drug does not develop under the near zero order profile of transdermal delivery. Because cutaneous metabolism is essentially an unknown variable, a given drug may not be a suitable candidate for transdermal delivery as it may be inactivated before it reaches the systemic circulation. Physiochemical criteria that should be taken into account when evaluating the feasibility of administering a drug transdermally included partitioning of the drug from the delivery system into the stratum corneum, diffusion of the drug across the stratum corneum, partitioning from the stratum corneum into the viable epidermis, and uptake of the drug by the cutaneous microcapillary network and subsequent systemic distribution. Pharmacokinetic relevant criteria can be determined by solving Ficks second law of diffusion for the delivery device, the stratum corneum, and the viable epidermis. Applications of these criteria were illustrated by applying them to determining the feasibility of administering nitroglycerin (55630), clonidine (4205907), and indomethacin (53861) transdermally.
NIOSH-Grant; Pharmaceuticals; Skin-absorption; Pharmacodynamics; Physiological-chemistry; Mathematical-models; Chemical-properties; Physical-properties;
Pharmacy University of California 926 Medical Sciences Building San Francisco, Calif 94143
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Transdermal Delivery of Drugs, Vol. III
University of California San Francisco, San Francisco, California