Question

Which of the following characteristics is suitable for transdermal drug?

(a) Large drug dose

(b) Large molecular size

(c) Drugs with narrow therapeutic indices

(d) Drugs which are metabolized in the skin

The question was posed to me in final exam.

This intriguing question originated from Biopharmaceuticals in section Biopharmaceuticals of Drug Biotechnology

Answer 1

Correct option is (c) Drugs with narrow therapeutic indices

The best I can explain: The transdermal route is unsuitable when the drug dose is large when the drug has a large molecular size, the drug is skin sensitizing and irritating. It also becomes a problem when the drug is metabolized in the skin, the drug goes protein binding in the skin, or even if the drug is highly lipophilic or hydrophilic.