Transdermal Patches

Transdermal drug delivery is a line of treatment that involves the delivery of medications in a non-invasive way through the surface of the skin. This is achieved through the placing of a transdermal patch which is a medical adhesive patch, on the skin to supply a specific dose of medicine via skin into the bloodstream. This heals the injured area of the body.  These patches find their use for administering nicotine, scopolamine, nitroglycerin, testosterone, and contraceptives. Also, the option of administering vaccine patches by marginally trained personnel or even patients themselves not only facilitates compliance with seasonal vaccination needs, but also accelerates vaccination campaigns in countries with scarce medical personnel. But then, only medications whose molecules are small enough to penetrate the skin can be delivered by this method. An extensive range of pharmaceuticals are now offered through transdermal patch form. Let us understand the transdermal patches from various angles.

Transdermal Patches

What is the difference

When medicines are administered via transdermal delivery, they score on some important factors when compared to the way they are given through oral or invasive ways. When medicines are taken orally, they undergo the liver’s first-pass effect which can prematurely metabolize drugs. In case of hypodermic injections, the administering is painful and often generates dangerous medical waste as well as poses the risk of disease transmission. Transdermal patches can be self-administered and are non-invasive. They can provide for long periods of release time (up to a week) and are generally inexpensive.

How it Works

A typical transdermal patch design has a reservoir that stores the drug. On one side, it is enclosed with impermeable backing while on the other side, it has adhesive which sticks to the skin. Some designs deploy drug dissolved in liquid or gel-based reservoir. This simplifies formulations and permits liquid chemical enhancers (like ethanol) usage. These designs usually have four layers: a backing impermeable membrane; a semi-permeable membrane that works as a rate-limiting barrier; a drug reservoir; and an adhesive layer. Other designs simplify manufacturing by incorporating the drug within a solid polymer matrix that combines drug into the adhesive.

Best Possible Use and Impact

Transdermal patches are best put to use in nicotine skin patches which offer great help to people who quit smoking. A source of nicotine through the patch helps reduce the withdrawal symptoms that the smoker experiences during the process of quitting. Hormonal patches like estrogen patches treat menopausal symptoms and post-menopausal osteoporosis. Motion sickness is commonly controlled through transdermal scopolamine. Elimination of the hypodermic needles further inspires transdermal vaccine development. Many a needle reuse has killed millions of people yearly from hepatitis B and AIDS.  In such scenarios, a needle-free, patch-based vaccination has a large impact.

Types of Patches

They are of 5 main types. Single-layer Drug-in-Adhesive system in which the adhesive layer sticks to various layers together. In a multi-layer one, one layer releases the drug instantly and the other controls drug release from a reservoir. Third is reservoir transdermal system that has a separate drug layer. A shallow compartment holds the drug reservoir. The matrix system, the fourth type, has a drug layer of a semisolid matrix comprising a drug solution. Fifth is the vapor patch, in which the adhesive layer holds various layers together and also releases vapor.

Side Effects

Skin, to which the patch is applied, can also act as a strong barrier. So only medications with small enough molecules to permeate the skin can be delivered. Adding pharmaceuticals like alcohol to substances within the patch for better skin penetration could end up irritating the skin. Again, adhesives on the bandage could cause allergies to foods, medicines or other substances. If the patch suffers a cut on any side of drug reservoir, the gel can leak from the reservoir exposing the patient to serious adverse effects like respiratory disorders. Again a leaked patch would be ineffective for treatment.

           Overall, transdermal drug delivery is the way ahead to address low bioavailability of various oral drugs; the inconvenience and agony of injections; and the limited controlled release options of both. Since their inception which was more than three decades ago, the transdermal patches have successfully expanded the delivering competencies for small molecules.   The technological advancements in this space position transdermal patches for great impact on medicine.

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