Use of Transdermal Drug Formulations in the Elderly

Abstract

Transdermal drug delivery systems are pharmaceutical forms designed to administer a drug through the skin to obtain a systemic effect. They ensure a constant rate of drug administration and a prolonged action. Several different types of transdermal delivery devices are available on the market. They are either matrix or reservoir systems and their main current uses are to treat neurological disorders, pain and coronary artery disease, and as hormone replacement therapy. Transdermal drug administration has a number of advantages compared with the oral route: it avoids gastrointestinal absorption and hepatic first-pass metabolism, minimizes adverse effects arising from peak plasma drug concentrations and improves patient compliance. Compared with the parenteral route, transdermal administration entails no risk of infection. For elderly people, who are often polymedicated, transdermal drug delivery can be a good alternative route of administration. Transdermal absorption depends on passive diffusion through the different layers of the skin. As skin undergoes many structural and functional changes with increasing age, it would be useful to know whether these alterations affect the transdermal diffusion of drugs. Studies have shown that age-related changes in hydration and lipidic structure result in an increased barrier function of the stratum corneum only for relatively hydrophilic compounds. In practice, no significant differences in absorption of drugs from transdermal delivery systems have been demonstrated between young and old individuals. The need for dose adaptation in elderly patients using transdermal drug delivery systems is therefore not related to differences in skin absorption but rather to age-related cardiovascular, cerebral, hepatic and/or renal compromise, and to ensuing geriatric pharmacokinetic and pharmacodynamic changes.

Appropriate use of transdermal drug delivery systems

“…Reservoir TDDS should not be cut, as altering the integrity of the system could create a dose-dumping effect that can lead to drug toxicity (including death) or inadvertent drug exposure to others [8,9] . Matrix (monolithic) systems contain a similar distribution of drug throughout the patch and exist in several forms including simple matrix systems, drug-in-adhesive system, and multilayer matrix systems [1] . All matrix TDDS incorporate active drug in a polymer matrix that regulates drug release via diffusion (i.e., drug concentrations moving from high concentrations to low concentrations) compared to reservoir systems which contain a rate-controlling membrane that is responsible for controlled release of transdermal formulations [1,5,10,11] .…”

“…In addition, transdermal formulations typically have a favorable drug concentration profile as the factors that limit gastrointestinal absorption (e.g., changes in pH, rate and extent of gastric emptying, transit times, presence/interaction with food, intestinal motilities) are avoided [1] . Delayed absorption prevents peaks and valleys associated with variations in drug concentrations.…”

“…Transdermal drug delivery systems (TDDS) are designed to administer drug products through the skin to provide systemic drug therapy [1,2] . Several advantages and disadvantages exist to this type of system.…”

“…In addition, the number of medications to be taken by elderly patients who are receiving many concomitant drugs may be reduced. Transdermal drug delivery may also be advantageous for patients who have difficulty swallowing tablets or have decreased venous access [1,4] .…”

“…In the elderly, the rate and extent of absorption may be delayed due to normal physiologic changes resulting in reduced adhesive effectiveness and/or physiologic changes in the skin [2] . Patients who have cognitive decline may forget they are wearing a patch, may administer several patches at a time, and experience additional adverse reactions [1] . In addition, several other factors (e.g., differences in patch designs, dosage or strength units, and abbreviations indicative of the patch's delivery system, administration frequency, and administration site) may confer additional confusion on the appropriate administration steps to use for the patch products [5] .…”