[A pharmacological profile of piracetam (Myocalm), a drug for myoclonus].

Abstract

Myoclonus is defined as shock-like, brief involuntary abnormal movements in muscle jerking caused by external stimuli; and it arises from progressive myoclonus epilepsy, post-anoxic encephalopathy and Alzheimer's disease, causing disabling symptoms. It is a rare syndrome but very difficult to control. Piracetam (2-oxo-1-pyrrolidineacetamide, Myocalm) was developed more than 30 years ago as a cyclic derivative of gamma-aminobutyric acid (GABA); it has been used in European countries for the treatment of memory loss and other cognitive defects in patients. Some reports have suggested that piracetam has anti-myoclonus activities, but the mechanisms of myoclonus are not well-identified, and thus there have been few preclinical studies on piracetam for the treatment of myoclonus. We investigated the effect of piracetam and clonazepam, an anti-epileptic drug, on high dosage urea-induced myoclonus using an electromyogram in rats. The incidence of myoclonus induced by urea 4.5 g/kg (i.p.) was significantly reduced by piracetam at 300 mg/kg (i.p.) and by clonazepam at 0.3 mg/kg (p.o.). The coadministration of piracetam 100 mg/kg (i.p.) and clonazepam at 0.03-0.1 mg/kg (p.o.) significantly reduced the incidence of myoclonus, although separate administration was not effective. After oral administration of piracetam, it is rapidly and completely absorbed and excreted almost unchanged in the urine; however, it does show a little binding to human serum protein. Repeated oral administration of piracetam for 7 days in phase-I trials did not show any accumulation of the drug. In the placebo-controlled double-blind crossover trial of piracetam conducted in the UK, there was a significant improvement in cortical myoclonus. In phase-II trials, piracetam inhibited myoclonus and showed an improvement in the quality of life (QOL) of the patients. These results show that piracetam has a beneficial use in clinics for severe myoclonus patients when it is combined with anti-epileptic drugs, demonstrating an improvement in the myoclonus and QOL of patients.

• Authors: K Tajima, M Nanri
• Journal: Nihon yakurigaku zasshi. Folia pharmacologica Japonica (Nihon Yakurigaku Zasshi) Vol. 116 Issue 4 Pg. 209-14 (Oct 2000) ISSN: 0015-5691 [Print] Japan
• PMID: 11084917 (Publication Type: English Abstract, Journal Article, Review)

Chemical References

• Anticonvulsants
• Neuroprotective Agents
• Nootropic Agents
• Clonazepam
• Urea
• Piracetam

Topics

• Animals
• Anticonvulsants (therapeutic use)
• Clinical Trials, Phase II as Topic
• Clonazepam (therapeutic use)
• Disease Models, Animal
• Drug Therapy, Combination
• Humans
• Myoclonus (drug therapy)
• Neuroprotective Agents (pharmacokinetics, therapeutic use)
• Nootropic Agents (pharmacokinetics, therapeutic use)
• Piracetam (pharmacokinetics, therapeutic use)
• Quality of Life
• Syndrome
• Urea (adverse effects)