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.)
Comments
DMSO was in the news in the 1980s, IIRC, amid controversy about its "miracle" properties of being able to cure just about any ache or pain. It was touted as a panacea rather than a drug delivery medium.
Posted by: Warren | July 13, 2007 11:15 AM
When i was an undergrad, the chemistry grad students would hold "DMSO Bowl" parties - they would triple distill DMSO in all brand new glassware and then smuggle it home. Each bowl was labelled with the substance dissolved therein. Everclear was popular (you had to take a hit off a homemade breathalyser to prevent accidental alcohol poisoning) but other substances of a variety of herbal or other dubious origins were also available.
I only went once, and i drank beer out of a bottle like normal. Way too intense for my tastes.
Posted by: Gelfling | July 13, 2007 11:49 AM
"DMSO Bowl" Parties?! Wow. I wonder what the homemade breathalyze consisted of.....
Posted by: Shelley | July 13, 2007 1:04 PM
I'm also curious as to how you make a homemade breathalyser.
http://www.tuckermax.com/archives/entries/date/the_famous_sushi_pants_story.phtml#277
Posted by: John | July 13, 2007 2:11 PM
John, that link was freaking hilarious although I'm quite sure I would feel tempted to kick that guy in the nuts if I ever met him. The below quote might mitigate the force of the blow, however:
"One guy calls it a "legitimate, certifiable science," while making air quotes with his fingers. I tell them that they are all (while imitating his air quotes) "legitimate, certifiable idiots" because they believe in horse-shit like energy healing. Two girls call me close-minded. I tell them that they are so open-minded that their brains leaked out."
Heh.
Posted by: Shelley | July 13, 2007 2:32 PM
IIRC, in the '80's it was common for horse trainers to use it to treat inflamed joints in racehorses. Naturally, it started to be diverted from veterinary use to human use. Alternative medicine folks raved about it. But unless it is handled very carefully, you can end up inadvertently getting all kinds of nasty things in it, which then get transported across the skin and absorbed. Plus, much of what was being passed around was industrial-grade, not pharmaceutical-grade product.
BTW I've treated a couple of people who have tried to abuse the fentanyl patches. The usually spend a day or two in the ICU before I see them. Needless to say, it is extremely dangerous. Having said that, the vast majority of people who get them, do not abuse them.
Posted by: Joseph j7uy5 | July 13, 2007 2:34 PM
Shelley - You are the prettiest Doctor that I ever saw! Something else!
Sorry - carry on with your doctor conversations. I just had to say that. :)
Posted by: Ese Loco | July 13, 2007 4:24 PM
Any idea wrt. the effectiveness of this drug?
I lost my grandfather to Alzheimers. It was very sad to see him go like that. Wouldn't want anyone else to go the same route.
Heh. That bowl party sounds like a wicked idea ;)
Posted by: Andre | July 13, 2007 4:31 PM
Ese, stand in line, you're not the first to notice.
I am kind of curious about the effects of pure DMSO, through --- it was being talked up in the late 60's too, as a cure for muscle pains and sprains. I hadn't realized that these patches use it.
Posted by: Charlie (Colorado) | July 13, 2007 7:30 PM
About the effectiveness of the patches, it is safe to say that something like that has to be on the market for about six months before you know how good it is and how bad it is (how likely it is to cause problems). Having said that, it almost certainly will be about as effective as the pill. The advantage will be with ease of use and patient compliance. Efficacy and effectiveness are nto the same thing. The drug only works if it actually gets into the patient's bloodstream. SO, while the effectiveness is probably the same, the efficacy is likely to be higher, if the compliance is higher (as it is expected to be).
Posted by: Joseph j7uy5 | July 14, 2007 1:34 AM
I heard a talk by Ronald Breslow from Columbia about his discovery that DMSO targeted some protein involved in cancer. Their group has extended that research into a pretty neat experimental drug. I bet it was a pretty odd moment, seeing a small molecule like DMSO do that.
Posted by: Jake | July 14, 2007 11:24 AM
At one point back in the '60's, DMSO was being used as an experimental cancer drug. Because of its ability to distribute throughout the body, patients being treated with DMSO had a characteristic "garlicky" breath odor. If you are careless and get it on your skin (which is easy to do because it is kind of greasy and hard to clean off of bottles) you can taste it, which is a bit disconcerting. It is a great solvent for compounds that are moderately hydrophobic, like steroids and benzodiazepines. I don't think it actually "carries compounds across the skin" as the common mythology would have it--just keeps them nicely in solution in a hydrophobic ionization state so that they can easily make their own way through membranes.
Posted by: trrll | July 14, 2007 9:32 PM
I made a short comment about DMSO on Deep sea news. Looks like birds "dig it", too.
Posted by: romunov | July 16, 2007 1:20 AM