RESUMEN
Seventy-two rats were used in this study to demonstrate the effect of histaminergic receptor blockers [H2 blockers]; namely, cimetidine or ranitidine, when administered 20 minutes prior to lidocaine on lidocaine induced central nervous system toxicity. The animals were classified into three main groups, each was further subdivided into four subgroups to study the effects of variable dosage regimens as follows: Intraperitoneal 30, 45, 60 or 75 mg/kg lidocaine alone or together with intraperitoneal cimetidine 15, 50, 100, or 200 mg/kg, respectively, or ranitidine 7.5, 25, 50 or 100 mg/kg, respectively. The results indicated that the lidocaine toxic dose was 60 mg/kg when given alone or with ranitidine while it was 45 mg/kg when lidocaine was combined with cimetidine. Again cimetidine also enhanced the convulsive effect of lidocaine and delayed its recovery period. In conclusion, ranitidine may be a safer component of premedication than cimetidine when adverse drug interactions, specially with local anesthetics, are considered