Transdermal ointments, creams and pastes consist of a semisolid medicine such as a paste or ointment where a quantity, usually specified in terms of length, is measured and rubbed into the skin. It can be rubbed into any non‐hairy area of skin. However, where a local effect is required (e.g. for NSAID gels) then the quantity should be rubbed over the affected area(s). Drugs that can be delivered in this way include glyceryl trinitrate and oestradiol. Disadvantages of transdermal preparations in these forms include that they can be messy for patients and can also result in variations of the dose delivered due to the amount applied, the amount of rubbing in of the product and the amount of product transferred onto clothing.

Numerous types of transdermal patch exist and their properties differ, so it is important to use them as directed. A transdermal patch (Figure 15.11) contains a certain amount of drug and delivers it in a controlled manner over a specific period of time that is sufficient to cause the desired pharmacological effect when the drug passes through the skin and systemically into the body. A major advantage of all transdermal patch systems is to deliver a drug at a constant rate over a prolonged period of time (Aulton and Taylor [16]). Drugs that can be delivered via a transdermal system include fentanyl, hyoscine, nicotine, rivastigmine, rotigotine and oestradiol (Aulton and Taylor [16]).

Three types of transdermal patch are available: drug in adhesive patches, drug in matrix patches and rate‐limiting membrane‐type patches.

The condition of the affected site should be assessed for altered skin integrity as applying medicines to broken skin can cause too‐rapid absorption, resulting in systemic effects (Perry [281]). The affected area must be washed and dried before applying the patch or ointment. Both patches and ointments should be applied to a hairless area of skin. The upper chest, upper arms and upper back are recommended sites and the distal areas of the extremities should be avoided (Chernecky et al. [39]). For local use (e.g. NSAID ointment) they should be applied to the relevant area of the body. Patches should not be trimmed or cut. It is important to remove previously applied patches as they will have residual drugs, which will continue to be absorbed and may lead to adverse effects.

A different skin site should be used each time to avoid skin irritation (Chernecky et al. [39]). After use, the patch still contains substantial quantities of active ingredients, which may have harmful effects if they reach the aquatic environment. Hence, after removal, the used patch should be folded in half (adhesive side inwards so that the release membrane is not exposed), placed in the original sachet (if still available) and then discarded safely out of reach of children. Any used or unused patches should be discarded according to local policy or returned to the pharmacy. Used patches should not be flushed down the toilet or placed in liquid waste disposal systems.