Anaphylactic-like reactions, history of atopy. Patients previously exposed to infections particularly chickenpox & herpes zoster. Performing invasive procedures. Hypomagnesaemia & hypocalcaemia; peripheral neuropathy, postural hypotension, seizures. Cumulative ototoxicity. Measure BUN, serum creatinine & CrCl prior to & during treatment. Perform peripheral blood counts, neurological exam & monitor electrolytes at regular intervals. Monitor liver function periodically. Avoid concomitant use of alcohol & aspirin. Not to be used w/ live vaccines. Avoid dental work during treatment. Hepatic impairment. Renal impairment, preexisting renal dysfunction. Avoid use during pregnancy. Not to be used during lactation.