DRUG-INTERACTIONS WITH INTRAVENOUS AND LOCAL-ANESTHETICS

Relatively few clinically significant drug interactions with anaesthet ics have been documented in the literature. The following should be st ressed since these interactions are not readily predictable or are pot entially fatal. Pethidine should never be administered to patients who have received monamine oxidase inhibiting drugs within the last fortn ight, since a fatal hyperpyrexia and/or hypertension may result. Thiop entone induction seems to make the heart more susceptible to arrhythmi as caused by adrenergic drugs, and may cause severe arterial hypotensi on in patients treated with diazoxide. Midazolam orally should possibl y be avoided as premedication in patients treated with erythromycin si nce anaesthetic concentrations of midazolam may result. patients for w hom bupivacaine analgesia is planned could preferentially be premedica ted with other drugs than diazepam, which causes the serum level of bu pivacaine to increase. Bradycardia and hypotension not attributable to sympathetic blockade have been reported following bupivacaine extradu rally in verapamil-treated patients. Sulfonamides and the ester group of local anaesthetics; such as prilocaine in combination, may result i n severe methaemoglobinaemia in infants. Epinephrine added to local an aesthetics may cause local vasodilation if administered to patients co ncurrently being treated with cyclic antidepressants, and the combinat ion imposes the risk of severe hypertension and arrhythmias.