Hypersensitivity to penicillins. History of allergy eg, bronchial asthma, rash, urticarial. Serious renal function disorder. Vit K deficiency may develop in patients w/ poor oral nutrition, receiving parenteral nutrition, elderly or in a debilitated state. False +ve results may occur in Benedict's & Fehling's soln, & clinitest. +ve direct Coomb's test may occur. Pregnancy & lactation. Premature & newborn infants.