Oral dantrolene prevents rise of myoglobin due to suxamethonium

Forty patients were studied in a randomised trial to investigate the effect of pre-operative oral dantrolene on the increase of serum myoglobin and creatinine kinase due to suxamethonium administration. Twenty patients in the treatment group were given 1.5 mg/kg dantrolene orally 4 hours pre-operatively. Blood was drawn immediately pre-induction and 5, 10 and 20 minutes after suxamethonium 1.2 mg/kg administration, following which surgery could commence. Myoglobin was measured by radioimmunoassay. The increase in mean myoglobin values was greatly reduced following suxamethonium in the treatment group (10.6 micrograms/litre at 20 minutes) compared to the control group (54.8 micrograms/litre at 20 minutes), (p less than 0.01). Total fasciculation score was not significantly reduced by the dantrolene pretreatment. No increase in creatinine kinase values occurred in any patient and the changes in mean potassium values in both groups were negligible. The only side effect attributed to dantrolene was pre-operative nausea in two patients. No interference with the action of suxamethonium, or difficulty with reversal was noticed. Oral dantrolene may be almost as effective as pretreatment with non-depolarising neuromuscular blocking drugs in preventing suxamethonium-induced increase in myoglobin with less interaction with other anaesthetic agents.