canklecat

Topical analgesics are much more complicated than that.

The above Pub Med article refers specifically to a combination of aspirin and ether applied topically to treat a limited range of neuropathic pain. It's not just aspirin or salicylate ointment rubbed on the skin. The common over the counter ointments containing salicylates sold for relieving muscle and joint pain will not and cannot work the same way as the ASA/diethyl ether (ADE) mixture cited in that article.

Even that specialized mixture has only been shown effective on a limited range of neuropathic pain -- the skin discomfort associated with shingles and similar herpes outbreaks.

Topical analgesics need to cross the skin barrier in most cases to be effective. Otherwise the stuff just sits on the skin and does little or nothing. The only thing aspirin-type salicylates do without a transdermal carrier is to relieve some types of acne and skin rashes due to psoriasis, etc.

MSM is the most common transdermal carrier used in over the counter topical analgesics. It delivers the analgesic components below the skin, just enough to reach surface level nerves, muscles, and joints. The theory is that it mostly reduces false pain signals from hyper-sensitized nerves, without significantly reducing real pain signals from current injuries. Products containing MSM include Stopain roll-on, gel and spray; Ted's Pain Cream; one type of Blue Emu (not all Blue Emu products) and one type of Biofreeze (not all). Most topical analgesics contain no MSM or other transdermal carrier, so they cannot penetrate the skin to reach the nerves.

For years farmers and ranchers used DMSO, a lab grade transdermal carrier sold as horse liniment. Some farmers and ranchers discovered they had some relief from arthritis in their own hands when they applied the stuff barehanded to horses. Adding aspirin/salicylate to the DMSO enhances the analgesic effect. But DMSO can be dangerous. It can also carry toxic/poisonous levels of nicotine, pesticides and other chemicals across the skin into the body. And DMSO can cause uncomfortable rashes with itching and burning. MSM is much better suited to human applications.

The theory -- which is being explored further by a UNT Dallas pain researcher -- is that the pain sensitized nerves become "stuck" long after the cause for the pain has been healed. So they're developing methods to reset the nerves to eliminate the false pain signals without numbing the necessary pain signals that tell us when something is wrong in the body due to injury or illness. If their research is successful it could produce treatments that bypass addictive opiates or long term use of NSAIDs to which the body can develop a tolerance or rebound effect.

For years topical analgesics without a transdermal carrier have approximated that effect by using a form of distraction: the topical ointment would produce another form of discomfort that temporarily distracted the patient from the original pain. Capsaicin was one of the most effective. At first it burns and can even produce blisters. With repeated application the skin surface nerves become desensitized to the pain caused by the capsaicin, which in turn desensitizes the surface level nerves to neuropathic pain from shingles, diabetes, and some muscle and joint pain.

The newer topical remedies produce the same effect without introducing new uncomfortable sensations -- burning, tingling, etc. For example, Ted's Pain Cream uses resveratrol, based on the theory that it helps reset hyper-sensitized nerves. User anecdotes indicate it works. The researchers (neuro scientists at UNT Dallas) are hoping to have this confirmed by independent research. But like many topical analgesics they include multiple ingredients which may complicate the study -- menthol or wintergreen oil, salicylates, arnica, others.

The folks who make Ted's Pain Cream are also planning to explore the use of cannabis as a topical analgesic. But this will probably also include a transdermal carrier like MSM.

I've tried one cannabis based topical analgesic and while it smelled pleasant it had no effect on my shoulder joint pain. It lacks a transdermal carrier. Even combined with DMSO or MSM it didn't seem to have any special effect. And the topical balm contained the other familiar ingredients -- menthol, camphor, etc. -- so it's impossible to say whether the cannabis had any effect.

I'm very doubtful about the efficacy of the many topical analgesics that contain only CBD and some form of oil or grease. Too much CBD marketing now relies on hype and anecdotes that may be motivated by placebo effect.