Effect of clorazepate in spasticity and rigidity: a quantitative study of reflexes and plasma concentrations

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Abstract
The effect of demethyldiazepam on increased myotatic reflexes, formed from its precursor clorazepate, was assessed in a double-blind cross-over study of 27 days duration. Patients (8) with spasticity or rigidity were given placebo or active substance: 1st in loading doses for 2 days, then 5 mg every 12 h for a total of 10 days. A wash-out period of 7 days was interposed between the two 10 day periods. Demethyldiazepam had a normalizing effect on the increased phasic ankle reflexes seen in spasticity, but not on the increased tonic reflex seen in rigidity. The mean concentration of demethyldiazepam in the steady state was 1227 nmol/l (range 600-1990 nmol/l). The plasma concentration of demethyldiazepam tended to correlate with the percent decrease in phasic reflex activity (P = 0.08, 2-tailed). A slight drowsiness in 2 patients as the only side-effect seen. Demethyldiazepam given as chlorazepate seems to be a suitable medicament in the treatment of spasticity.