Infliximab
Infliximab is a chimeric monoclonal antibody that binds to and neutralises the endogenous inflammatory cytokine tumor necrosis factor alpha (TNF-α). Infliximab is used in the treatment of autoimmune conditions, including inflammatory bowel disease (IBD), inflammatory arthritis and plaque psoriasis.
- To guide dose-adjustment to optimise drug efficacy
- Exposure-response relationship of intravenous infliximab is well established in patients with IBD and positive associations are observed in patients with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis and plaque psoriasis.
- Patients at risk of increased infliximab clearance may benefit the most from TDM.
- Diagnosis
- Differentiating disease refractory to infliximab versus inadequate drug exposure
Assay detail
See Canterbury Health Labs TNF Biologic Drugs assay information.
Timing of concentration sample collection
- Blood samples should be taken at the drug trough, within 24 hours prior to the next dose.
| Disease | Induction | Maintenance |
| IBD | 20-25 mg/L at week 2 15-20 mg/L at week 6 |
7-10 mg/L at week 14 5-10 mg/L after week 14 >10 mg/L in perianal fistulising Crohn’s disease and acute severe ulcerative colitis |
| Rheumatoid arthritis | No recommendation | 3-7 mg/L |
| Spondyloarthritis | ≥6-7 mg/L | |
| Plaque psoriasis | >2-5 mg/L | |
| Hidradenitis suppurativa | No recommendation |
Dose individualisation and adjustment
- The presence of antibodies to infliximab (ATIs) can lead to high clearance and low concentrations of infliximab. Some laboratories will do reflex testing of ATIs if infliximab is below a certain level (e.g. <2 mg/L).
- Patients with active IBD activity may have a degree of protein losing enteropathy and/or bowel bleeding, which can lead to increased infliximab clearance by drug leaking into the bowel. Infliximab dose and/or dosing frequency may need to be increased to help attain adequate drug exposure.
- Certain genetic variants can alter infliximab pharmacokinetics and treatment response. For instance, variants in the HLA-DQA105 allele are linked to increased risk of immunogenicity and loss of response. TDM can guide dosing escalations in patients carrying genetic variants.
- Children typically exhibit higher infliximab clearance relative to body weight and require more frequent dosing optimisation.
Other dosing considerations
- Some patients may have non-TNF-α driven disease, and therefore, may be unresponsive to infliximab despite high serum concentrations.
- No dose adjustments are necessary for hepatic and renal impairment.
- Dose adjustment may result in dosing outside of that which is Medsafe-approved and/or Pharmac funded.
Medicines Information: phone 03 364 0900 or email medicines.information@cdhb.health.nz
- Alsoud D, Moes et. al . Best Practice for Therapeutic Drug Monitoring of Infliximab: Position Statement from the International Association of Therapeutic Drug Monitoring and Clinical Toxicology. Ther Drug Monit. 2024; 46:291-308.
- Barclay ML, Karim S, Helms ETJ, Keating PE, Hock B, Stamp LK, Schultz M. Infliximab and adalimumab concentrations and anti-drug antibodies in inflammatory bowel disease control using New Zealand assays. Intern Med J. 2019; 49:513-518
Last updated
October 2024