Drug Delivery


The evolution of Transdermal Drug Delivery and treating migraine


Oral drug delivery is the most common and convenient route of drug administration due to a high rate of patient compliance, cost-effectiveness, portability, ease of production and pre-determined dosage.


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owever, there are limitations with oral drug delivery, such as incomplete deliv- ery due to the unpredictability of gas-


trointestinal absorption. Parenteral route of administration, such as injection, is another com- mon drug delivery method. Advantages of par- enteral drug delivery include rapid onset of action and circumvention of gastrointestinal degradation of the drug, but this method is invasive and some- times painful. It also has a lower rate of patient compliance and requires a trained administrator. Transdermal Drug Delivery (TDD) is a promis-


ing method for drug application that has major advantages over some of the most common routes of drug administration. TDD involves the non- invasive delivery of medications through the skin surface and when applied can deliver the drug at a predetermined rate across the skin to achieve either a local or systemic effect.


History of transdermal delivery development Transdermal delivery of medications is not a new concept. The use of transdermal delivery of home- made medicinal preparations dates to the early 20th century. Mustard plasters were used for severe chest congestion. The Belladonna Plaster, containing 0.25% of Belladonna alkaloid, had a place in the US pharmacopeia as a transdermal analgesic. Perhaps the most remarkable forerunner of modern transdermal medication was Stronger


Drug Discovery World Winter 2018/19


Mercurial Ointment, used as a treatment for syphilis when Salvarsan and other arsenicals were in use, before the discovery of penicillin. Even the composition of this ointment was remarkable; it contained 50% of elemental mercury!


First-generation TDD TDD offers advantages over conventional par- enteral or oral routes. They ensure controlled absorption and more uniform plasma drug concen- trations. Bioavailability is improved by avoiding first-pass hepatic metabolism and enzymatic or pH-associated deactivation. The first generation of TDD is responsible for


most of the transdermal patches that have thus far been in clinical use. More than 30 years ago the nicotine patch revolutionised smoking cessation by continuously suppressing the smoker’s craving for a cigarette. Catapres® is the first patch that delivers seven-


day dosing of clonidine to hypertensive patients who otherwise would have to adhere to taking one tablet twice a day. This is the first example of a non-injectable sustained-release dosage form that achieves seven-day delivery for a small molecule. It demonstrates the therapeutic benefit of a dosage form that can sustain a flat blood level profile and has the convenience of a once-a-week dosing for chronic treatment. DURAGESIC® transformed post-surgical breakthrough pain care by providing a non-oral,


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By Dr Mahmoud Ameri and Hayley Lewis


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