Oritavancin
A single-dose lipoglycopeptide with three separate mechanisms against gram-positive bacteria, useful for one-and-done skin infection treatment but notorious for scrambling coagulation lab tests for days afterwards.
Also known as lipoglycopeptide, oritavancin diphosphate, Orbactiv, Kimyrsa, LY333328
Approved drug — Licensed by a major regulator for human use, with phase-3 trial data behind it.
FDA-approved in 2014 on the SOLO I and SOLO II randomised non-inferiority trials against twice-daily vancomycin in acute bacterial skin infection. Use outside skin infection, including for bacteraemia or osteomyelitis, is not supported by randomised data and is complicated by the osteomyelitis signal in the pivotal trials.
How it works
Oritavancin is a semisynthetic derivative of the vancomycin relative chloroeremomycin. Like all glycopeptides it binds the D-Ala-D-Ala terminus of lipid II, but its hydrophobic biphenyl side chain also anchors it in the membrane and allows a second interaction with the pentaglycyl bridging segment of peptidoglycan — a site that vanA-modified precursors do not alter, which is why oritavancin retains activity against vancomycin-resistant enterococci. Its third mechanism is direct membrane depolarisation and permeabilisation, giving it rapid concentration-dependent bactericidal activity uncommon for a glycopeptide. Its terminal half-life of about ten days comes from extensive tissue distribution and slow release. The molecule also binds phospholipid reagents in coagulation assays, artefactually prolonging aPTT for up to 48 hours and PT/INR for up to 24 hours after a dose.
Targets: Lipid II D-Ala-D-Ala terminus, Peptidoglycan pentaglycyl bridge, Bacterial cytoplasmic membrane
Dosing
| Protocol | Dose | Frequency | Route |
|---|---|---|---|
| Single-dose regimen for acute bacterial skin infection (Orbactiv)Infused over 3 hours. | 1200 mg | once, as a single dose | intravenous |
| Single-dose regimen (Kimyrsa formulation)Infused over 1 hour. | 1200 mg | once, as a single dose | intravenous |
- · 1200 mg once, diluted in 5% dextrose. This is the entire course.
- · Same 1200 mg dose in a reformulated product that shortens infusion time to one hour and allows saline or dextrose as diluent — the main practical difference between the two brands.
Titration
No dose adjustment for mild to moderate renal or hepatic impairment. Severe impairment has not been studied.
Cycling
One dose is the complete course. Repeat dosing within a fortnight has not been studied and is not recommended.
Pharmacology
- Half-life
- Terminal half-life of roughly 245 hours, about 10 days.
- Onset
- Rapid bactericidal killing during and immediately after the infusion; clinical response assessed at 48-72 hours.
- Routes
- intravenous
- Molecule
- Semi-synthetic lipoglycopeptide derived from chloroeremomycin
- Sequence length
- 7 amino acids
- Molecular weight
- 1793.1 Da
Handling
- Diluent
- Sterile water for injection, then diluted in 5% dextrose (Orbactiv) or dextrose/saline (Kimyrsa)
- Typical mix
- 40 or 40 mL
- Vial sizes
- 400, 1200 mg
- Lyophilised
- Room temperature, 20-25°C.
- Reconstituted
- Infusion must be completed within 6 hours at room temperature or 12 hours refrigerated.
Mixing
Each 400 mg Orbactiv vial takes 40 mL of sterile water; three vials are needed per dose. Swirl, do not shake. Orbactiv is incompatible with saline — use dextrose only, and flush the line with dextrose before and after.
Side effects
- very commonInterference with coagulation tests— Artefactually prolongs aPTT for up to 48 hours and PT/INR for up to 24 hours. It does not actually cause bleeding, but it makes heparin monitoring impossible and has led to inappropriate transfusion when misread.
- commonNausea and vomiting
- commonHeadache
- commonInfusion-site reactions and phlebitis— Three-hour infusion of a large-volume dextrose solution irritates peripheral veins.
- uncommonOsteomyelitis in trial patients— More cases of osteomyelitis were reported in the oritavancin arms of the phase 3 trials than in comparators; the label carries this as a warning.
- uncommonHypersensitivity reactions— Can appear days after the dose given the long half-life.
Do not use if
- Intravenous unfractionated heparin sodium within 48 hours of an oritavancin dose — this is a labelled contraindication because aPTT becomes uninterpretable.
- Known hypersensitivity to oritavancin or other glycopeptides.
- Not appropriate where gram-negative or anaerobic coverage is required.
Combining it
- conflictunfractionated heparin — Contraindicated for 48 hours after a dose because aPTT-guided heparin dosing cannot be performed safely.
- cautionwarfarin — Oritavancin is a weak CYP2C9 inhibitor and also distorts INR measurement, so warfarin control becomes unreliable for a day or more.
- redundantdalbavancin — Same clinical niche; dalbavancin avoids the coagulation-assay problem.
What to monitor
- · Do not use aPTT-based heparin monitoring for 48 hours after dosing; use anti-Xa levels instead if anticoagulation is required.
- · Clinical wound and cellulitis assessment at 48-72 hours.
- · Because a single dose lingers for weeks, any hypersensitivity reaction needs supportive management rather than drug withdrawal.
Legal status
Prescription-only injectable, approved in the US and EU for acute bacterial skin and skin-structure infections.
References
- Corey et al. 2014-2015, SOLO I and SOLO II trials of single-dose oritavancin (trial)
- Orbactiv (oritavancin) US prescribing information (label)
- Kimyrsa (oritavancin) US prescribing information (label)
Mechanism in depth
A lipoglycopeptide with three mechanisms rather than one - D-Ala-D-Ala binding like vancomycin, secondary binding to the pentaglycyl bridge, and direct membrane depolarisation. The additional mechanisms give it activity against vancomycin-resistant organisms that pure D-Ala-D-Ala binders lose.
What usually goes wrong
The coagulation assay interference is the trap. A prolonged aPTT after oritavancin looks like a bleeding disorder, and acting on it - withholding anticoagulation, transfusing, investigating - is a response to an artefact. It also makes unfractionated heparin unmonitorable for that window, so heparin is contraindicated for 48 hours after a dose.
Bloodwork worth running
| Marker | When | Why it matters |
|---|---|---|
| Coagulation screen awareness | Avoid drawing these tests in the window after dosing where possible. | Oritavancin binds phospholipid reagents and artefactually prolongs aPTT for up to 48 hours and PT/INR for up to 24 hours. The blood is not anticoagulated; the test is wrong.Act if: A prolonged aPTT in this window should not be treated as a coagulopathy. |
Pharmacokinetics
- Protein binding
- 85%
- Crosses blood-brain barrier
- no
- Accumulates
- Yes — doses stack before steady state
- Elimination
- Slow, largely unchanged
Receptor targets
- D-Ala-D-Ala terminus, pentaglycyl bridge, and bacterial membrane — Multi-site
Cell wall inhibition plus membrane depolarisation; retains activity against VanA organisms
What to expect, and when
Single dose, immediate concentrations, sustained for over a week.
Genuinely uncertain
- As with dalbavancin, use beyond skin and soft tissue infection rests largely on observational data.