Oritavancin

Oritavancin is a semisynthetic lipoglycopeptide antibiotic used for the treatment of acute bacterial skin and skin structure infections (ABSSSI) caused by susceptible Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA). It belongs to the glycopeptide class and exerts its antimicrobial effect by inhibiting cell wall synthesis: it binds to the D-alanyl-D-alanine terminus of peptidoglycan precursors and disrupts transglycosylation and transpeptidation; in addition, it can disrupt bacterial membrane integrity, contributing to bactericidal activity against many Gram-positive pathogens.

For ABSSSI, oritavancin is administered as a single intravenous infusion of 1200 mg given over about three hours. Its long half-life allows one-dose therapy, with the drug detectable for extended periods. Oritavancin has broad in vitro activity against Gram-positive bacteria, including MRSA, MSSA, Streptococcus species, and Enterococcus faecalis; activity against Enterococcus faecium and some vancomycin-resistant strains varies and should be guided by susceptibility data. It has limited activity against most Gram-negative bacteria and is not indicated for polymicrobial infections where Gram-negatives predominate.

Adverse effects are generally mild to moderate and common ones include nausea, diarrhea, vomiting, headache, and infusion-related reactions. Hypersensitivity and hepatic enzyme elevations may occur. A notable consideration is that oritavancin can interfere with certain coagulation tests (for example, INR and aPTT), potentially leading to falsely altered results for several days after administration; this can complicate anticoagulation monitoring and surgical planning.

Contraindications include known hypersensitivity to oritavancin or related compounds. Pregnant or lactating individuals should be considered carefully, as data are limited. Resistance remains uncommon but may arise with reduced susceptibility in some strains; use should be guided by local susceptibility patterns.