A skin-patch (similar to the patches that deliver nicotine trans-dermally) has been approved to treat Alzheimer’s disease. The drug in the patch, Exelon (rivastigmine), is already on the market in pill form, but in the form of a patch the drug can be delivered continuously and more reliably. Delivery through the skin also gets rid of any nasty gastrointestinal side-effects (probably appreciated by caregivers as well…). Rivastigmine is a cholinesterase inhibitor; it works to prevent the breakdown of acetylcholine in the brain. This is theorized to slow or mitigate the symptoms of dementia which, in many cases, is preceded by the death of cholinergic neurons and a subsequent decrease in acetylcholine. The drug increases those levels of acetylcholine.
I’ve always been interested in how these skin patches work, specifically what they contain that transfers the enclosed drugs into the skin. After a quick search I found that one common ingredient in many transdermal patches is the chemical DMSO (if you are in a lab, you may have heard of it). DMSO (dimethyl sulfoxide) is a solvent and a by-product of the wood industry. In 1961 a Dr. Jacob noted that the chemical was able to penetrate the skin deeply without causing any damage. Later it was observed to be a superior solvent for pharmaceuticals, and capable of transporting chemicals across and into skin (for better or worse). Obviously you’d want to be careful with DMSO (for example, LSD is sometimes dissolved in DMSO), but these properties made it quite useful for introducing therapeutic drugs into the skin via the patch. The release of drug was constant and predictable, and patches were difficult to abuse (the strong painkiller fentanyl is sometimes delivered this way.)