This is not exactly a "drug"...it is a chemially altered (and therefore can have a patent to make $$) of arginine, which is an amino acid used OTC as a supplement to improve circulation.

Some mechanisms for PN involve loss of circulation, or damage to the small vessels around nerves. Then the nerves cannot get nutrients or get rid of metabolic byproducts properly and then become damaged or dead. So by improving blood flow, it is thought that this one kind of PN may be helped. Arginine is also found in many OTC erectile support supplements.

The downside of arginine is that viruses in the body use this amino acid to replicate. The classic example is the shingles virus, Herpes Zoster, which lives in people for life who have been infected with chicken pox. One mechanism for people with full body pain is suggested to be a viral trigger of some sort, which then damages the dorsal roots along the spine and in people with a genetic inability to repair this damage, remains a problem for life with sensory disturbances. Most people with viral damage do get better as the nerve growth factors repair this damage. But a small % have the genetic defect and cannot repair. Research is going on now, to perhaps create a stem cell therapy for this type of problem.

So arginine is a stimulus for triggering dormant viruses. It is the major downside to using it regularly for various treatments IMO.
Another virus implicated like the Zoster, is Epstein Barr.

I've seen commonly many patients in long term care with bedsores, being given high dose Arginine to help heal them.
Within a short time, those on the Arginaid products (medical food product powder) end up with a Shingles attack on top of the bedsore problem!

Have you read the AlkaSeltzer threads here? Please search that, because if you respond to AlkaSeltzer original formula, it will tell you that your pain, is inflammatory and perhaps acidic.
The AlkaSeltzer has always worked for me, but because it contains aspirin, it should be used only in bursts to avoid any bleeding side effects over time that aspirin causes. AlkaSeltzer has the aspirin in solution which protects the stomach somewhat but systemically over time the aspirin affects platelets. So if it does work for you, doctor supervision is required for long term use. (Do not use the Cold or flu products, as they have different ingredients and are not the same). WalMart has their Equate brand which is very very inexpensive-- just over $2.00 for 36 doses. It is a huge savings.