Infliximab is a biologic, monoclonal-antibody drug.

The United States Food and Drug Administration has approved Infliximab in the following cases (with doses mentioned):

• For moderate to severe, active Crohn disease in adults and children (six years and above) who have had a non-satisfactory response to conventional therapy, the induction dose is 5 mg/kg, given as intravenous therapy at 0, 2 and 6 weeks, followed by maintenance therapy at the same dosage every eight weeks. In patients who do not benefit from the lower dose, 10 mg/kg is considered  [1]
• For moderate to severe, active ulcerative colitis in adult patients with an unsatisfactory response to conventional therapy, the usual dose is 5 mg/kg intravenously (IV) at 0, 2, and 6 months as the initial dose, followed by 5 mg/kg every 8 weeks for maintenance. [2]
• For moderate to severe, active rheumatoid arthritis, induction therapy at 3 mg/kg is given at 0, 2, and 6 weeks, followed by maintenance therapy every 8 weeks. 
• With active ankylosing spondylitis, a dose of 5 mg/kg IV is given at 0, 2, and 6 weeks, followed by dosing every 6 weeks.
• With active psoriatic arthritis, a dose of 5 mg/kg IV is given at 0, 2 and, 6 weeks, followed by dosing every 8 weeks.
• For chronic severe plaque psoriasis in adult patients, a dose of 5 mg/kg IV is given at 0, 2, and 6 weeks, followed by dosing every 8 weeks. 

Although there is little supporting data, studies have shown that infliximab is not effective in very young patients. A study published in 2014 showed a remission rate of 36% in one year in patients younger than 7 years as compared to a remission rate of 88% in older children. The remission achieved in older children is comparable to that achieved in adults. [3]

It is also used off-label (not FDA-approved) to treat the following conditions:

• Bechet disease
• Relapsing polychondritis
• Juvenile idiopathic arthritis 
• Pyoderma gangrenosum
• Pustular psoriasis 

This drug may be given in combination with methotrexate to avoid possible immunologic responses by the host which would decrease or blunt the effect of the drug. 

Infliximab is a type of biologic therapy/immunotherapy designed to stimulate our body's immune system and treat certain diseases. Infliximab is a monoclonal antibody that inhibits tumor necrosis factor-alpha (TNF-a). TNF-a is a signaling protein involved in acute phase reaction and systemic inflammation. It is produced by macrophages, CD4+ lymphocytes, NK cells, neutrophils, mast cells, eosinophils, and neurons. This inhibition of TNF-a stops the cascade of the inflammatory reaction, leading to the improvement of the disease condition (psoriasis, Crohn disease, etc.). Infliximab is a chimeric protein that contains both murine and human components. In adults, it has been shown to have a half-life of 7 to 12 days.[4]

Infliximab is administered via an intravenous route. It has been shown to cause type I and type III hypersensitivity reactions in the studies conducted.

A variety of strategies are used to prevent infliximab-induced infusion reaction, including the following:

• Administering antihistamine and acetaminophen 90 minutes before the infusion
• Using a test dose of infliximab
• In patients with a prior history of anaphylaxis reaction to infliximab, administering prednisone, antihistamine, and acetaminophen prior to infusion

Dosage Adjustments

• In patients with mild heart failure (NYHA class I/II), no dosage adjustment is required, but caution and monitoring are needed.
• In patients with severe heart failure (NYHA Class III/IV), dosage adjustment is required, such that the dose is kept less than or equal to 5 mg/kg.
• In patients with renal or hepatic impairment, no dosage adjustments have been advised.[5][6]

Infliximab is a generally safe and a well-tolerated medication, but as the dose or the age of the patient (greater than 60 years) increases, there are heightened chances of side effects:

• Reports of infections are more common in patients taking additional immunosuppressive therapy
• Infusion-related reactions (fever, pruritis, anaphylaxis, etc.)
• Headache
• Nausea
• Abdominal pain
• Dyspepsia
• Diarrhea
• Constipation
• Hepatotoxicity - There have been reported cases severe enough to be fatal and to necessitate a liver transplant.
• Heart failure
• Anemia, leukopenia, neutropenia, thrombocytopenia - patients should seek immediate medical care if they develop symptoms of an infection.
• Demyelination disease
• Paradoxical reaction
• Tuberculosis reactivation
• Malignancy - half of the cases reported are lymphomas
• Reactivation of Hepatitis B
• Psoriasis
• Vitiligo or other autoimmune disorders - antinuclear antibody has been positive in patients taking infliximab with normal baseline levels.
• Transient vision loss - has been reported within 2 hours of infusion, stopping the drug is advisable if serious

Infliximab has been shown to cross the placenta and is present in the serum of babies whose mothers were given infliximab during pregnancy for up to 6 months. CLincians have seen agranulocytosis and reactions to live vaccines in these infants. Therefore, a wait of 6 or more months is the recommendation in exposed infants before administering live vaccines.

Patients have developed antibodies (human anti-chimeric antibodies) against infliximab, which not only lowers the efficacy of the drug but also causes infusion reactions. To reduce this risk, co-administration of other immunosuppressors like methotrexate should be a consideration.

Infliximab can be administered with care in certain conditions, but the following conditions are defined as a contraindication to infliximab administration:

• Heart failure (NYHA class III/IV) - According to the American Heart Association, TNF inhibitors may cause myocardial toxicity or may exacerbate the underlying myocardial dysfunction.
• Previous hypersensitivity reaction to infliximab
• Current severe infection (sepsis, tuberculosis)
• Active infection

Use infliximab with caution in the following conditions:

• Preexisting demyelinating disease
• Mild to moderate heart failure (NYHA classI/II)
• History of seizures

It is known to cause a cross-reaction with some drugs (eg., abatacept, adalimumab, etanercept), so care is administered when the patient is on another medicine.