No 500mg carisoprodol is FDA-approved — only 250mg and 350mg exist in the USA. This 2026 guide covers how carisoprodol works via its meprobamate metabolite, why the 2-to-3-week limit is essential, DEA Schedule IV status since 2012, dangerous interactions with opioids and alcohol, withdrawal warning signs, and a 7-drug muscle relaxant comparison table.