What is a patch?
Patches are a means of delivering certain drugs into the body through the skin. The patches are self-adhesive with the sticky side attaching to the skin and holding the patch in place. The drug is contained within the patch in a ‘reservoir’ and is gradually released through a special ‘membrane’. This membrane controls the release of the drug, meaning the patient gets a steady level of drug in their bloodstream over a prolonged time period. Figure 1 provides a diagram to explain the patch formulation.
Figure 1. Diagrammatic representation of a patch
Patches offer many advantages, such as prolonged steady levels of the drug in the bloodstream and are a convenient alternative for patients who have difficulties swallowing their medicines. Another advantage is that if the patient experiences side effects, the patch can simply be removed to stop the drug from entering the bloodstream. However, because the skin is a very good barrier, and is designed to keep things out of the body, only a limited number of drugs can cross the skin and thus be formulated as a patch. When people think of patches, they will perhaps think of nicotine patches that can be bought in pharmacies, but other medicines such as certain painkillers can also be administered through a patch.