Hypersensitivity. Severe immunodeficiency states (eg, AIDS). Significantly impaired bone marrow function or significant anaemia, leucopenia, neutropenia or thrombocytopenia. Severe active infection until resolution. Severe hypoproteinaemia (eg, in nephrotic syndrome). Severe hepatic impairment (Child-Pugh class C). Severe renal impairment undergoing dialysis. Pregnant or women of childbearing potential who are not using reliable contraception during treatment & thereafter as long as plasma levels are >0.02 mg/L. Lactation.