Regarding percutaneous absorption of drugs from transdermal patches, which of the following statements are true?

• A. ALL statements are correct
• B. Only ONE statement is correct
• C. TWO statements are correct
• D. THREE statements are correct

Answer: (A)

The key idea is how transdermal patches deliver drugs through the skin and how multiple true statements about that process can line up to all be correct. The stratum corneum is the main barrier, so absorption depends on the drug’s ability to partition into and diffuse through this lipid-rich layer—typically favoring small, moderately lipophilic molecules with suitable molecular weight. The patch design controls release, often producing a near-steady input over time, which supports stable plasma levels and minimizes fluctuations compared with some other routes. Because the first-pass liver metabolism is bypassed, systemic exposure is mainly governed by how fast the drug is released from the patch and how readily it permeates the skin. Factors like skin hydration, occlusion, site of application, and the condition of the skin can alter permeability, while formulation features (adhesive, backing, and any enhancers) shape the delivery rate and potential for irritation. If the statements presented cover these well-established aspects—barrier behavior, influence of physicochemical properties, steady release with systemic exposure, and modulation by skin and formulation—they are all true, making the option that all statements are correct the best choice.