How does transdermal drug delivery work?
Transdermal drug delivery involves delivering a medicine to the body’s blood circulation system by absorption through the skin. The first medicine to be delivered in this way was glyceryl trinitrate (a drug used to treat angina) in the form of an ointment. However, it is difficult to control or reproduce the amount of medicine delivered with ointments because the delivery depends on the amount applied, which isn’t easy to measure accurately. So manufacturers have developed adhesive patches, which allow control of the amount of medicine delivered to the circulation. In addition to opioid patches, a number of other drugs are delivered in this way: • Nicotine (to prevent cravings while an individual tries to stop smoking). • Nitroglycerin (for patients with angina). • Oestrogen (for women going through the menopause). For a drug to be absorbed via the skin into the bloodstream, the drug molecules must pass through the top two skin layers – the epidermis and dermis – into the capillaries (
