Erythromycin is a macrolide antibiotic that inhibits bacterial protein synthesis by targeting the 50S ribosomal subunit, blocking the progression of nascent polypeptide chains.[1] It is effective against a host of bacterial genera, including Streptococcus, Staphylococcus, and Haemophilus (MIC90s range from 0.015-2.0 mg/l).[2] Erythromycin is known to potently inhibit the cytochrome P450 isoform CYP3A4, which can affect the metabolism of numerous clinically relevant medications.[3],[4] Erythromycin lactobionate is a soluble salt of erythromycin that is typically used for intraperitoneal or intravenous injections.[5],[6]