Antibacterials for systemic use, Beta-lactam antibacterials, penicillins, Beta-lactamase sensitive penicillins.

Penicillin is a beta-lactam antibiotic which has bactericidal activity against mainly Gram-positive bacteria and some Gram-negative aerobes. It is sensitive to beta-lactamase (penicillinase) inactivation. It is widely distributed in the extracellular fluids after absorption, and eliminated almost entirely by the kidneys.

The procaine penicillin gives high initial blood levels; treatment may be repeated at 24 or 48 hour intervals to maintain therapeutic levels.