Adalimumab

Adalimumab is a fully human monoclonal IgG1 anti-TNF antibody given by subcutaneous injection, used across rheumatoid arthritis, spondyloarthritis, psoriatic arthritis, juvenile idiopathic arthritis, psoriasis, hidradenitis suppurativa, uveitis, Crohn disease and ulcerative colitis. Biosimilar versions are widely used and are not distinguished here.

Class. Anti-tumour necrosis factor monoclonal antibody.

Mechanism. Neutralises soluble and transmembrane TNF alpha, blocking its binding to p55 and p75 receptors.

Pharmacokinetics. Subcutaneous bioavailability about 64 percent, half-life about 2 weeks, steady state by about 5 months without methotrexate. Anti-drug antibodies lower levels and are less common with methotrexate co-therapy.

Rheumatoid arthritis. 40 mg subcutaneously every other week with methotrexate. Without methotrexate, 40 mg every week or 80 mg every other week may be used. Loading dose: none.

Psoriatic arthritis and ankylosing spondylitis or axial spondyloarthritis. 40 mg every other week.

Plaque psoriasis. Loading dose 80 mg once, then 40 mg every other week starting one week later. Increase to 40 mg weekly or 80 mg every other week for inadequate response after 16 weeks.

Crohn disease. 160 mg at week 0, 80 mg at week 2, then 40 mg every other week; escalate to 40 mg weekly or 80 mg every other week for loss of response.

Ulcerative colitis. 160 mg at week 0, 80 mg at week 2, then 40 mg every other week; continue only if there is clinical response by week 8.

Hidradenitis suppurativa. 160 mg at day 1 (as 4 injections in one day or 2 on 2 consecutive days), 80 mg at day 15, then from day 29 either 40 mg weekly or 80 mg every other week.

Non-infectious intermediate, posterior and panuveitis. 80 mg once, then 40 mg every other week starting one week later.

Juvenile idiopathic arthritis (2 years and over). 10 mg every other week for 10 to under 15 kg, 20 mg for 15 to under 30 kg, 40 mg for 30 kg and over.

Maximum dose. 80 mg every other week in rheumatological use; 40 mg weekly in other labelled escalations.

Contraindications. Active tuberculosis or other severe infection (sepsis, opportunistic infection), moderate to severe heart failure, and hypersensitivity.

Boxed-warning-level risks. Serious infections (tuberculosis, invasive fungal, bacterial) and malignancy including hepatosplenic T cell lymphoma.

Adverse effects. Common: injection site reactions, upper respiratory infection, headache, rash, raised liver enzymes. Serious: tuberculosis and hepatitis B reactivation, demyelination, lupus-like syndrome, cytopenias, worsening heart failure, serious infection, new or worsening psoriasis, hypersensitivity.

Major interactions. Anakinra and abatacept (avoid), other biologics, live vaccines (avoid), and cyclophosphamide (infection and malignancy risk).

Common prescribing errors. No tuberculosis and hepatitis B screening; stopping methotrexate and losing response; dosing interval confusion between weekly and every other week.

Special groups.

• Pregnancy: can be continued through the second trimester where disease control requires; many specialists stop between 28 and 32 weeks in stable remission to limit placental transfer. If given late, delay live vaccines in the infant for 12 months.

• Breastfeeding: compatible.

• Children: 10, 20 or 40 mg every other week by weight band (2 years and over).

• Older adults: higher infection risk; check cardiac status.

• Kidney impairment: no adjustment.

• Liver impairment: no adjustment; monitor enzymes.

• Region: tuberculosis, hepatitis B and endemic fungal infection screening is essential; the cold chain needs 2 to 8 degrees Celsius and the pen may stay at room temperature up to 14 days.

Formulations. 40 mg and 80 mg prefilled pens or syringes (and lower strengths for children). Inject into the thigh or abdomen, rotating sites. Store refrigerated, protected from light, and do not freeze.

Baseline. Tuberculosis screen, hepatitis B and C and HIV serology, full blood count, liver enzymes, chest radiograph, vaccination update, and pregnancy test.

Monitoring. Disease activity and infection symptoms at each visit; full blood count and liver enzymes periodically (3 to 6 monthly). Trough levels and antibodies in inflammatory bowel disease when response falls.

Stop or hold thresholds. Serious infection, demyelination, lupus-like syndrome, heart failure, malignancy, or severe hypersensitivity. Hold during surgery or active infection and restart when resolved.

Referral and escalation. Specialist initiated. Refer for primary or secondary non-response and for any serious infection.