Moderate-spectrum penicillins: amoxicillin and ampicillin

The aminopenicillins, amoxicillin and ampicillin, have better activity than benzylpenicillin against some gram-negative bacteria (eg Escherichia coli, Haemophilus influenzae), but are inactivated by strains that produce beta-lactamase enzymes. They are the drugs of choice for susceptible enterococcal infections. Amoxicillin is preferred to phenoxymethylpenicillin for oral treatment of Streptococcus pneumoniae infections because amoxicillin has a longer half-life and higher oral bioavailability, leading to higher overall drug exposure.

When given parenterally, amoxicillin and ampicillin are equivalent.