Patients received between 2 and 10 doses of 1,200 mg IV given every 6 to 14 days. Johnson and colleagues report using oritavancin 1,200 mg IV every other day for 3 doses followed by 1,200 mg IV once weekly for a patient with daptomycin- and vancomycin-resistant Enterococcus endocarditis, resulting in negative blood cultures while on therapy. 9 However, source control via valve replacement and postoperative oritavancin 1,200 mg IV twice weekly for 10 weeks was required to fully clear the infection.
Schulz and colleagues published a retrospective cohort analysis of 17 patients who received multiple doses of oritavancin for complicated bacterial infections, including osteomyelitis, pneumonia, and bacteremia. 10 They reported 100% of patients were either successfully cured or had demonstrable improvements in their infections by using a 1,200 mg IV loading dose followed by 800 mg IV if the second dose was given within 7 days or 1,200 mg IV if the second dose was given more than 10 days later. Patients received between 2 and 18 total doses, with 6 out of 17 (35%) receiving only 2 doses. One patient who received 18 doses was an outlier, as her treatment goal was palliative suppression due to an infected endovascular graft that could not be removed.
In a published case series, 1 of 10 patients receiving oritavancin for invasive Grampositive infections received multiple doses of oritavancin for an MSSA deep tissue infection. 11 The 3 total doses (strength not reported) were separated by 19 days and 14 days and resulted in cure. Several case reports and a retrospective chart review study specifically show the effectiveness of oritavancin for osteomyelitis caused by MSSA, MRSA, and VRE. 12-16 However, dosing strategies varied widely after the initial 1,200 mg IV loading dose.
Drug Interactions, Safety, and Tolerability
Oritavancin has minimal drug-drug interactions, the most notable being with anticoagulants. 1 Use of IV heparin within 120 hours of oritavancin administration can falsely elevate activated partial thromboplastin time (aPTT) levels; therefore, heparin should not be monitored with aPTT during this period. Oritavancin also can artificially prolong international normalized ratio (INR) values for up to 12 hours, and dose adjustments based on INRs during this window are not recommended. Of note, factor Xa laboratory monitoring is unaffected by oritavancin, as it does not depend on phospholipid reagents as do aPTT and INR measurements.
Oritavancin has been shown to be well tolerated when dosed according to both the package insert and continued dosing strategies. The most common adverse effects (AEs) (≥ 3%), occurring at similar rates to vancomycin, are nausea, vomiting, diarrhea, headache, and limb and subcutaneous abscesses. 1 Infusion reactions also have been reported, although they are usually reversible on slowing or stopping the infusion. It is worth noting that the use of oritavancin for osteomyelitis is not recommended in the product labeling, as an increased rate of osteomyelitis was observed in the oritavancin vs IV vancomycin groups for the treatment of patients with acute bacterial skin and skin structure infection (SOLO) trials (0.6% in oritavancin group vs 0.1% in vancomycin group, statistical significance not reported). 17 However, it was postulated that these osteomyelitis cases were likely present, yet not recognized, at baseline and were not the result of administering oritavancin. This conclusion is further corroborated by previously presented research demonstrating successful cure of osteomyelitis with continued dosing strategies. 12-16