On the down-side: The main disadvantage to transdermal delivery systems is the innate barrier function of the skin. There’s also a molecular weight issue, since many molecules are simply too large to pass through intact skin. Although there are new technologies being investigated to allow transdermal delivery of larger molecules, insulin for example, cannot pass through the skin without modification, as the molecules are too big. Other factors such as the thickness of the stratum corneum, the hydration level of the skin, body temperature, existing or underlying skin disease or in- juries, as well as ethnic differences can all affect the absorption rate of transdermal medications.
Some patch-drug ingredients need to be combined with alcohol or other permeation enhancers to increase skin penetration ability, which can cause skin irritation. Constant application of a patch, to the same site, can also cause irritation or in the case of nitro-glycerin patches, overwhelm the body. Despite these considerations, a wide variety of pharmaceuticals are now available in transdermal patch form.
Some of the well-known medicated patches include: the nicotine patch; pain-control patches; anaesthetic patches; hormone patches; angina pectoris patches; hypertension patches; anti-inflammatory patches; motion sickness patches; vitamin B12 patches; various vitamin, mineral and herbal patches; anti-depression patch; ADHD patch for hyperactivity; Alzheimer’s patch; and osteoarthritis patches.
Patches with aromatic essential oil-releasing vapours are available for the following conditions: respiratory congestion, insomnia, addiction, beauty/aesthetic, health and wellness, stress-reduction, libido enhancement.