Which statement correctly describes the location of the drug in a reservoir-type patch?

• A. Drug is contained in reservoir between backing layer and rate controlling membrane.
• B. Drug is dispersed within an adhesive matrix.
• C. The drug sits beneath the backing layer with no membrane.
• D. The drug is delivered through microneedles.

Answer: (A)

In a reservoir-type patch, the drug is kept in a separate liquid or gel reservoir that is enclosed within the patch. This reservoir sits between the backing layer (the outer protective layer) and the rate-controlling membrane (which sits toward the skin). The rate-controlling membrane governs how fast the drug leaves the reservoir and enters the skin, providing a steady, predictable release.

This arrangement keeps the drug from being mixed into the adhesive, which is what happens in adhesive-matrix patches. If the drug were simply under the backing layer with no membrane, there would be little or no control over the release rate. Microneedles describe a different delivery approach altogether, not an ordinary reservoir patch.