Hypersensitivity to penicillins. Not to be given in patients w/ infectious mononucleosis. Risk of Jarisch-Herxheimer in patients w/ syphilis. High-dose use. Not be mixed w/ proteinaceous fluids eg, protein hydrolysates, blood or plasma, or w/ IV lipid emulsions. Severe renal impairment (CrCl <10 mL/min). Pregnancy & lactation.