Pharmacology · Interleukin inhibitors
Ustekinumab !
An antibody against p40, the piece shared by IL-12 and IL-23, for psoriasis, psoriatic arthritis, Crohn disease and ulcerative colitis.
Updated 2026-11-01
The figure shows IL-12 bound to the ustekinumab Fab at its p40 subunit.
Mechanism of action
Ustekinumab is a human IgG1 monoclonal antibody against p40, the subunit common to IL-12 and IL-23. It stops both cytokines from binding their receptor chain IL-12Rβ1 on T cells and NK cells, which reduces Th1 responses (IL-12) and the Th17 axis (IL-23), the main drivers of psoriasis and inflammatory bowel disease.
- Antibody binds the p40 subunit
- IL-12 and IL-23 cannot reach their receptor
- Th1 and Th17 responses fall
- Skin and gut inflammation settles
Pharmacokinetics
- Absorption
- Subcutaneous injection; an intravenous infusion is used for the first dose in bowel disease
- Metabolism
- Broken down like other antibodies
Indications
- Plaque psoriasis Psoriasis →
- Psoriatic arthritis Psoriatic arthritis →
- Crohn disease Crohn disease →
- Ulcerative colitis Ulcerative colitis →
Adverse effects
Common
- Upper respiratory infections, runny nose
- Headache, tiredness
- Injection-site redness
- Nausea, vomiting, diarrhoea
Contraindications
- Hypersensitivity to ustekinumab
- Active serious infection, including active tuberculosis
Key interactions
- BCG vaccine
- Not given during treatment and for a year afterwards; recent BCG is reported before starting.
- Live vaccines
- Risk of infection from the vaccine strain; avoided during treatment, and vaccines are updated before starting.
What is monitored
- Latent tuberculosis test before starting
- Signs of infection
- Skin checks for cancer
- New neurological symptoms (headache, confusion, seizures)
Administration and safety
- Subcutaneous injection; the intravenous form is infused over at least an hour by staff.
- The first subcutaneous dose is given in the clinic.
Nursing care
- Before the first dose, confirm the latent tuberculosis test (and hepatitis B screening where ordered) and that vaccines are up to date.
- Do not give the dose during an active infection; teach to report fever, cough, burning on urination or hot, red skin.
- Live vaccines are avoided during treatment; any vaccine is discussed with the team first.
- Ask about BCG vaccination in the past year and about allergy shots (immunotherapy).
- Teach to report sudden severe headache, confusion or vision changes at once.
Pregnancy and breastfeeding
Human data are limited; the treating team weighs benefits and risks, and the baby's doctor is told before live vaccines.
Test yourself
Think of the answer, then tap the question to see it.
Why does a single antibody block both IL-12 and IL-23?
Ustekinumab binds p40, a subunit present in both cytokines.
Which vaccine is specifically avoided during ustekinumab treatment and for a year after?
BCG (and live vaccines in general).
Which rare neurological syndrome is a warning with ustekinumab?
Posterior reversible encephalopathy syndrome: sudden headache, confusion, seizures, vision changes.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Ustekinumab Injection: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 39 (McGraw Hill, 2023); Altered Immunocompetence | Vaccines & Immunizations | CDC (Centers for Disease Control and Prevention (CDC), 2024); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.