As an OTC supplement, I occasionally use Sceletium Tortuosum extract, which is marketed under the trademark Zembrin. Sceletium Tortuosum is a South African succulent plant that has been chewed by the San tribe people for thousands of years under the name Kanna. (recall Nǃxau ǂToma in "The Gods Must Be Crazy")
There have been recent peer reviewed studies showing it both safe and effective, and placebo or not, I have noted relief of my symptoms. It's also rather inexpensive compared to a lot of other supplements, at around $0.30 for a daily dose.