Hypersensitivity reactions
Serious hypersensitivity reactions, including anaphylactic reactions and anaphylactic shock have been reported with the use of oritavancin. If an acute hypersensitivity reaction occurs during oritavancin infusion, oritavancin should be discontinued immediately and appropriate supportive care should be instituted.
No data are available on cross-reactivity between oritavancin and other glycopeptides, including vancomycin. Before using oritavancin, it is important to inquire carefully about previous hypersensitivity reactions to glycopeptides (e.g. vancomycin, telavancin). Due to the possibility of cross-hypersensitivity, there should be careful monitoring of patients with any history of glycopeptide hypersensitivity during and after the infusion.
Infusion related reactions
Oritavancin is given via intravenous infusion over 3 hours, to minimise the risk of infusion-related reactions. Intravenous infusions of oritavancin can cause reactions such as flushing of the upper body, urticaria, pruritus and/or rash. Infusion-associated reactions characterised by chest pain, chest discomfort, chills, tremor, back pain, neck pain, dyspnoea, hypoxia, abdominal pain, and fever have been observed with the use of oritavancin, including after the administration of more than one dose of oritavancin during a single course of therapy. If reactions do occur, stopping or slowing the infusion may result in cessation of these symptoms (see section 4.8).
Need for additional antibacterial agents
Oritavancin is active against Gram-positive bacteria only (see section 5.1). In mixed infections where Gram-negative and/or certain types of anaerobic bacteria are suspected, oritavancin should be co-administered with appropriate antibacterial agent(s).
Concomitant use of warfarin
Oritavancin has been shown to artificially prolong prothrombin time (PT) and international normalised ratio (INR) for up to 12 hours, making the monitoring of the anticoagulation effect of warfarin unreliable up to 12 hours after an oritavancin dose.
Interference with assay for coagulation tests
Oritavancin has been shown to interfere with certain laboratory coagulation tests (see sections 4.3 and 4.5). Oritavancin concentrations that are found in the blood of patients following administration of a single dose have been shown to artificially prolong:
• aPTT for up to 120 hours,
• PT and INR for up to 12 hours,
• Activated Clotting Time (ACT) for up to 24 hours,
• Silica Clot Time (SCT) for up to 18 hours, and
• Dilute Russell's Viper Venom Test (DRVVT) for up to 72 hours.
These effects result from oritavancin binding to and preventing the action of the phospholipid reagents which activate coagulation in commonly used laboratory coagulation tests. For patients who require aPTT monitoring within 120 hours of oritavancin dosing, a non-phospholipid-dependent coagulation test such as a Factor Xa (chromogenic) assay or an alternative anticoagulant not requiring aPTT monitoring may be considered.
The Chromogenic Factor Xa Assay, the Thrombin Time (TT) assay and the assays, used for the diagnosis of Heparin Induced Thrombocytopenia (HIT) are not affected by oritavancin. In vitro, oritavancin 46.6 μg/mL did not affect an assay for activated protein C resistance (APCR), suggesting that there is a low likelihood that oritavancin will interfere with this test. However, APCR is a phospholipid-based test and it cannot be ruled out that higher concentrations of oritavancin that may occur during clinical use could interfere with this test.
No effect of oritavancin on the in vivo coagulation system was observed in nonclinical and clinical studies.
Clostridioides difficile-associated diarrhoea
Antibacterial-associated colitis and pseudomembranous colitis have been reported for oritavancin and may range in severity from mild to life threatening diarrhoea. Therefore, it is important to consider this diagnosis in patients who present with diarrhoea subsequent to the administration of oritavancin (see section 4.8). In such a circumstance, the use of supportive measures together with the administration of specific treatment for Clostridioides difficile should be considered.
Superinfection
The use of antibacterial medicinal products may increase the risk of overgrowth of non-susceptible micro-organisms. If superinfection occurs, appropriate measures should be taken.
Osteomyelitis
In Phase 3 ABSSSI clinical trials, more cases of osteomyelitis were reported in the oritavancin-treated arm than in the vancomycin-treated arm (see section 4.8). Patients should be monitored for signs and symptoms of osteomyelitis after administration of oritavancin. If osteomyelitis is suspected or diagnosed, appropriate alternative antibacterial therapy should be instituted.
Abscess
In the Phase 3 clinical trials, slightly more cases of newly emergent abscesses were reported in the oritavancin-treated arm than in the vancomycin-treated arm (4.6% vs 3.4%, respectively) (see section 4.8). If newly emergent abscesses occur, appropriate measures should be taken.
Limitations of the clinical data
In the two major trials in ABSSSI, the types of infections treated were confined to cellulitis, abscesses, and wound infection only. Other types of infections have not been studied. There is limited experience in clinical studies in patients with bacteraemia, peripheral vascular disease' or neutropenia, in immunocompromised patients, in patients aged > 65 years, in patients with severe renal impairment and in infections due to Streptococcus pyogenes.