Mephenesin is a centrally acting muscle relaxant. It can be used as an antidote for strychnine poisoning. Mephenesin however presents with the major drawbacks of having a short duration of action and a much greater effect on the spinal cord than the brain, resulting in pronounced respiratory depression at clinical doses and therefore a very low therapeutic index. It is especially dangerous and potentially fatal in combination with alcohol and other depressants. Mephenesin was used by Dr. Bernard Ludwig and Dr. Frank Milan Berger to synthesize meprobamate, the first tranquilizer to see widespread clinical use. Mephenesin is no longer available in North America but is used in France, Italy and a few other countries. Its use has largely been replaced by the related drug methocarbamol, which is better absorbed

• Chlorphenesin
• Guaifenesin, a structurally-related compound used as an expectorant
• Mephenoxalone
• Methocarbamol