[Cardiac failure caused by an overdose of dantrolene]

A case is reported of cardiac failure with repeated pulmonary oedema in a female patient suffering from renal failure and having been given incremental doses of dantrolene sodium. On withdrawal of the drug, all symptoms disappeared. This muscle relaxant was considered not to have any depressive myocardial side-effects. However, recent studies on isolated myocardial fibres showed the existence of a constant dose-dependent negative inotropic effect of dantrolene sodium, only noticeable with high concentrations of the drug.