Effects of bromocriptine on parkinsonism. A nation-wide collaborative double-blind study.

The effects of bromocriptine in patients with Parkinson's disease manifesting various problems in levodopa therapy were tested in a double-blind manner with the collaboration of 59 institutions. The slow and low principle was in part adopted. Either bromocriptine or placebo was added to levodopa. Twenty-nine % of the bromocriptine-treated patients (n = 108), in contrast to 14.8% of the placebo-treated (n = 108), showed either marked or moderate improvement (P less than 0.05). Twenty to 37% improvement was noted in most of the symptoms studied in those treated with bromocriptine. The significant superiority of bromocriptine was also noted in the effects on wearing-off phenomena and frozen gait. No irreversible side effects were noted. It is concluded that bromocriptine is useful in patients who are manifesting various difficulties in levodopa therapy. Our results are comparable to those using higher maintenance doses. Dopamine antagonistic actions were not observed. This is unlike the case with experimental animals.