Kinetics of Distribution of Radioactive-Labeled Muscle Relaxants I. Investigations with C14-Dimethyl-d-Tubocurarine

A trace of C14-dimethyl-d-tubocurarine was administered intravenously to 26 control dogs and to 26 dogs under induced conditions of prolonged hypoxia, hypercapnia, shock and hypothermia. Fifteen hours subsequent to administration to the controls 0.8 per cent of the drug was still in plasma, 85 per cent was eliminated in the urine and 14 per cent was distributed in the extravascular space. Radiochromatographic scannings suggested that C14-dlimethyl-d-tubocurarine remains unchanged in the body of the dog. Seventy per cent of the C14-dimethyl-d-tuhocurarine was bound to human plasma in vitro.—After trace injection, a moderate amount of labeled curarine (of the order of 10-5 of the administered dose) crossed the blood-brain barrier and appeared in cerebrospinal fluid. During the abnormal conditions a slower disappearance from plasma, impaired urinary elimination, higher and persistent accumulation in the extravascular space and increased passage into the CSF were found.