Pregnancy and lactation. Patients with penicillin allergy. Avoid prolonged use as pivalate-containing compounds may cause carnitine deficiency over time; greater risk of carnitine deficiency in patients with renal impairment or decreased muscle mass. May decrease prothrombin activity especially in patients with renal or hepatic impairment, poor nutritional status, prolonged antibiotic treatment or patients previously stabilised on anticoagulant therapy. Long term use may result in development of drug-resistant bacteria, or superinfection including Clostridium difficile-associated diarrhoea and pseudomembranous colitis. Lactation: excretion in milk unknown; use with caution