Pharmacology of Infliximab

Infliximab is an important medicine used in the treatment of autoimmune diseases such as Crohn’s disease and ulcerative colitis. Here, we outline what the drug is used for, how it works, and what side effects and drug interactions its linked to.

Infliximab belongs to a class of medicines known as monoclonal antibodies. Through the suffix -mab, we can identify member drugs of this growing class.

The drug is marketed as Remicade in the United States.

Infliximab is used to treat autoimmune conditions such as:

  • Crohn’s disease
  • Ulcerative colitis
  • Psoriatic arthritis
  • Rheumatoid arthritis
  • Ankylosing spondylitis
  • Plaque psoriasis

Infliximab is not administered orally. If it were, the medicine would be destroyed by gastric juices. Instead, it is administered via the IV route – usually every 6 to 8 weeks – dosing in mg per kg of the patient’s weight.

Mechanism of action

Infliximab is a chimeric mouse-human IgG monoclonal antibody.

It works as an inhibitor of TNF-alpha (TNF: tumor necrosis factor); a cytokine responsible for many effects of the autoimmune response, including:

  • Induction of proinflammatory cytokines – IL-1 and IL-6, for example.
  • Leukocyte migration – moving leukocytes from blood vessels into tissues.

Infliximab binds to TNF-alpha, meaning the cytokine no longer activates its target receptors. Infliximab targets both soluble (freely available in the blood) and transmembrane (outer portion of various immune cells) forms of TNF-alpha.

Through these means, infliximab reduces inflammation and pain associated with a variety of autoimmune diseases.

Side effects

Side effects with infliximab include:

  • Viral infection – upper respiratory tract
  • Bacterial infection
  • Cough – often secondary to infection
  • Headache
  • Abdominal pain
  • Bronchitis
  • Hot flushing
  • Fatigue
  • Chills
  • Dizziness
  • GI effects – nausea, vomiting, diarrhea
  • Elevated blood pressure
  • Chest pain
  • Muscle pain
  • Rash
  • Abnormal liver function tests
  • Neutropenia / leucopenia

Many of these effects can be summarised as follows – first, as effects caused by reducing the immune response (infections, cough, neutropenia etc.); second, as pains (abdominal pain, chest pain, muscle pain, headache); and third, as allergic-type symptoms (rash, chills, flushing, dizziness etc.).

Clinical considerations

When we talk about the clinical pharmacology of infliximab, we need to think about the following factors:

  • That both adults and children should not be administered live vaccines while taking infliximab.
  • That infliximab is administered via the IV route. Local injection site reactions are not uncommon.
  • That infliximab is administered every 6-8 weeks. Even after last administration, the drug is detectable in the body for up to 8 weeks.
  • That given infliximab dampens the immune response, caution is warranted in patients at risk of serious, latent infections – such as tuberculosis and hepatitis B. Risk factors should be evaluated, and tests should be performed, to determine whether the patient is safe for infliximab treatment. These risks are not limited to infliximab but for TNF-alpha inhibitors generally – including etanercept and adalimumab.
  • That due to this response, older patients and children are at greater risk to suffer infections, even fatal infections, due to the mechanism of infliximab.
  • That infliximab is classified as pregnancy category B – meaning “no risk in non-human studies”.
  • That the risk of infection increases when infliximab is taken with other medicines that dampen the immune response. This includes other monoclonal antibodies such as adalimumab, etanercept and certolizumab.

Though infliximab comes with a wide variety of serious side effects, it remains a highly effective means to induce and maintain remission for autoimmune diseases that go unresponsive to other treatment forms.

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