Phenprobamate (3-phenylpropylcarbamate, Gamaquil, Isotonil) is a centrally acting muscle relaxant with mild sedative and anticonvulsant effects. Muscle relaxants can enhance and prolong the effect of narcotic drugs and enable to obtain same effect with a smaller amount of alcohol or illicit substance. Almost all of the centrally acting muscle relaxants have varying sedative effects on which their abuse potential mainly depends. Overdose is similar to barbiturates. Its mechanism of action is probably similar to meprobamate. Phenprobamate was previously used in humans as an anxiolytic, and is still sometimes used in general anesthesia and for treating muscle cramps and spasticity. Phenprobamate is still used in some European countries, but it has generally been replaced by newer drugs. Phenprobamate is metabolized by oxidative degradation of the carbamate group and ortho-hydroxylation of the benzene ring, and is eliminated in urine by the kidneys. Doses range from 400 to 800 mg, up to 3 times a day.