Eight patients who had skeletal muscle spasticities due to spinal cord injuries received various combinations of four drugs, (1) zoxazolamine, (2) a placebo resembling zoxazolamine, (3) chlorpromazine, and (4) a placebo resembling chlorpromazine. Each patient's status with respect to muscular spasticities was evaluated objectively by observers who, like the patient himself, did not know which combination of drugs he was receiving at a given time. The dosages used were 500 to 1,000 mg. of zoxazolamine and 25 to 50 mg. of chlorpromazine, all given four times a day, and were sufficient to cause some side-effects (drowsiness, nausea) in six of the eight patients. These dosages did not, however, have any consistent effect on muscular spasticity in this series of patients.
Gibson JW, Bluestone SS, Lowman EW. ZOXAZOLAMINE AND/OR CHLORPROMAZINE FOR MUSCLE SPASM. JAMA. 1957;165(1):18-20. doi:10.1001/jama.1957.02980190020004