Increased cardiac autonomic irritability w/ cyclopropane & halothane anaesth. Severe, prolonged HTN w/ MAOIs or triptyline- or imipramine-type antidepressants. Incompatible w/ alkalis & oxidising agents, barbiturates, chlorpheniramine, chlorothiazide, nitrofurantoin, novobiocin, phenytoin, Na bicarbonate, Na iodide, streptomycin, sulfadiazine, sulfafurazole.