Table 1.

Advantages versus disadvantages of transdermal drug delivery.

Advantages

Patient and carer satisfaction because of ease of use and tolerability

Limiting hepatic first-pass metabolism, hence lower dose of medication can obtain desired

lasma level compared with oral formulations

Reduced frequency of dosing

Constant drug serum level versus episodic peaks

Reduced side effects secondary to gastrointestinal intolerance and fluctuations of drug levels

Avoidance of unpleasant and inconvenient parental administration

Easier to titrate to achieve optimal therapeutic doses

Potentially reduces the risk of drug overdose

Removal of the patch stops drug delivery

Disadvantages

Slow time towards peak plasma levels

Unsuitable model for emergency treatments that requires rapid release of desired drug and rapid serum levels

Limited choice of medication that may be formulated in transdermal format

Variations in bioavailability (see Table 2)

Skin sensitivity and application allergic reactions

Steady state of drug is maintained only as long as the patch is applied

Good adherence to skin is necessary for patches to be effective. Presence of oil, hair or sweat on the patch application site can be hindrances to adherence and can cause variations in absorption.

TDS involves learning the appropriate application technique

Potential medication error such as using multiple patches

TDS can be costlier than oral formulations

Complex issues such as:  monitoring cumulative effects of long-term use  emerging research evidence and lack of randomized controlled trials and economic evaluation  ethical and legal dilemmas in situations where capacity and consent to treatment are in question