The efficacy and safety of proquazone 150 mg and proquazone 75 mg was compared to placebo in a double-blind, randomized, parallel, multi-investigator study in the acute treatment of muscle contraction (tension) headache.

Of the 122 patients entered into the study, 5 were subsequently discontinued, and 117 patients (39 in each of the three treatment groups) were included in the efficacy analyses.

The effects of proquazone 150 mg on all of the symptoms associated with the muscle contraction (tension) headache symptom complex, namely pain, psychic tension and muscle stiffness of the head, neck and shoulders, were significantly superior to both proquazone 75 mg and placebo. These results were consistent using both a patient self-rating form and a physician's global evaluation of patient response to study medication. For the pain parameters, proquazone 75 mg also showed significant superiority to placebo indicating a dose related clinical effect of proquazone. Only four patients reported transient adverse effects after taking the study medication, which were considered to be mild in nature, and none required therapeutic intervention.