What is a patch?
Patches are designed to enable drugs to pass through the relatively impermeable skin into the body and are often referred to as TTS (transdermal therapeutic systems). Due to the effectiveness of the skin as a barrier this route is only suitable for chemicals with the appropriate characteristics and for drugs where only small doses are required for therapeutic effect. Figure 1 provides a diagrammatic representation of a patch formulation.
Figure 1. Diagrammatic representation of a patch
By utilising patches as a method of drug administration the release of the drug can be controlled and therefore peaks and troughs in the drugs level in the body can be avoided. If a patient suffers side effects the patch can be removed and furthermore patches can hold sufficient amounts of the drug to enable them to only require changing after extended periods of time.
Patches can be used to deliver a variety of drugs for a wide range of conditions and therefore may provide an alternative to tablets and capsules in some patients.
Examples of patch formulations include:
- Hyoscine patches for motion sickness or hypersalivation.
- Fentanyl & buprenorphine patches for pain.
- Nicotine patches to aid smoking cessation.
- Glyceryl trinitrate patches for angina and heart failure.
- Oxybutynin patches for incontinence.