[Over-additive increase of the toxicity of lidocaine by pethidine]

The influence of LD50 of lidocain by preliminary treatment with pethidin, aminophenazone or diazepam, respectively, is examined at the mouse. When pethidine is given within 1/100 to 1/10 of its LD50 develops a dose-dependent increase of toxicity for lidocaine. In 10 mg pethidin/kg the LD50 for lidocain decreases about the half. Under the conditions chosen amino phenazone and diazepam had no influence on the toxicity of lidocaine. It is referred to clinical aspects when pethidine and lidocain are simultaneously applied.