Penicillins By Brian J Werth, PharmD, University of Washington School of Pharmacy Reviewed / Revised May 2022 | Modified Sep 2022 View Patient Education Pharmacokinetics Indications Contraindications Use During Pregnancy and Breastfeeding Adverse Effects Dosing Considerations More Information Topic Resources Penicillins Penicillins are beta-lactam antibiotics that are bactericidal by unknown mechanisms but perhaps by activating autolytic enzymes that destroy the cell wall in some bacteria.