Myoclonus levodopa

Klawans HL, Goetz C, Bergen D. Levodopa-induced myoclonus. Arch Neurol 1975 32 330-334. 

Dyskinesias occur in up to 80% of patients receiving levodopa therapy for long periods. The form and nature of dopa dyskinesias vary widely in different patients but tend to remain constant in character in individual patients. Chorea, ballismus, athetosis, dystonia, myoclonus, tics, and tremor may occur individually or in any combination in the face, trunk, or limbs. Choreoathetosis of the face and distal extremities is the most common presentation. The development of dyskinesias is dose-related, but there is considerable individual variation in the dose required to produce them. 

In 40 patients (mean age 64 years, 22 men) who took tolcapone for 3-7 months and were given entacapone in dosages titrated to 800-2000 mg/day after a transition period of 3-6 months with co-beneldopa, the improvements in on and off times were less impressive than they had been with tolcapone and there were more adverse effects (3). One patient had diarrhea and orthostatic hypertension with both drugs, but another six patients had increased dyskinesias and hallucinations and one developed myoclonus. There was no evidence of liver toxicity with either drug. The authors pointed out that entacapone, unlike tolcapone, not only increases the half-life of levodopa but also its peak concentration, causing significantly enhanced levodopa-related adverse effects. There is therefore a paradox entacapone appears to be safer but overall causes more adverse effects. 

---