Table 1

Experimental in vitro muscle contracture test upon exposition to neuroleptic agents

CompoundMinimum concentration (μg/ml)Maximum concentration (mg/ml)Concentration level causing relevant contracture (>2 mN)
Muscle bundles from a fresh biopsy (about 2.5 cm long, 200 mg each) were exposed to neuroleptics in geometrically increasing concentrations. All other conditions were analogous to the European Malignant Hyperthermia Group IVCT protocol.5 Atypical neuroleptics were less prone to cause pathological muscle contractures. In muscle biopsy specimens of MH patients, no contractures could be observed in the same experimental setting (not shown).
Clozapine12.52.0No contracture
Sulpiride12.55.011
Olanzapine2.55.09
Risperidone1.01.08
Fluphenazine1.250.67
Haloperidol2.51.06
Perazine2.52.56
Flupenthixol12.52.01