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Systemic immunomodulators in dermatology
Every "classic" systemic drug in dermatology has a typical risk profile that sets the pre-treatment tests and monitoring: methotrexate — bone marrow and liver, ciclosporin — kidney and blood pressure, acitretin — prolonged teratogenicity, azathioprine — TPMT, dapsone — G6PD.
Why it matters in the exam
The exam shows a patient on methotrexate for psoriasis who develops pancytopenia after starting trimethoprim-sulfamethoxazole, a young woman who asks whether she can take acitretin and become pregnant in a year, or a patient on ciclosporin with a rising creatinine and hypertension. The question tests the required tests, interactions and limits: methotrexate is given once weekly with folic acid, and with trimethoprim the risk of marrow suppression rises; ciclosporin suits rapid control and short-term use; acitretin is forbidden in pregnancy for 3 years after stopping and alcohol must be avoided during treatment; TPMT is checked before azathioprine; G6PD is checked before dapsone; apremilast causes diarrhoea, weight loss and mood changes; and hydroxychloroquine requires periodic retinal screening and a dose not exceeding 5 mg/kg real body weight per day. Remember that before any immunosuppression tuberculosis, hepatitis and vaccination status must be checked, and that in chronic disease the drug is also chosen by comorbidities, such as fatty liver, kidney failure or a wish to conceive.
Key points
- Every classic systemic drug in dermatology has a typical risk profile that sets tests and monitoring.
- Methotrexate is given once weekly with folic acid, and needs monitoring of blood count, liver and kidney and avoidance of trimethoprim.
- Ciclosporin suits rapid control and short-term use, and needs creatinine and blood pressure monitoring.
- Acitretin is teratogenic for 3 years after stopping, and alcohol must be avoided during treatment.
- TPMT is checked before azathioprine, G6PD before dapsone, and hydroxychloroquine requires periodic retinal screening.
Summary table
| Drug | Mechanism and use | Main risks | Tests and monitoring |
|---|---|---|---|
| Methotrexate | Antifolate; psoriasis, atopic dermatitis, pemphigoid | Marrow suppression, liver injury, lungs; teratogenic | Blood count, liver and kidney tests; folic acid; no trimethoprim |
| Ciclosporin | Calcineurin inhibitor; rapid control of psoriasis and atopic dermatitis | Kidney damage, hypertension, interactions via CYP3A4 | Creatinine and blood pressure; short course; not with phototherapy |
| Acitretin | Retinoid; pustular psoriasis, lichen planus, SCC prevention in transplant recipients | Teratogenic for 3 years after stopping; lipids; liver | Pregnancy tests, lipids and liver tests; no alcohol |
| Azathioprine and mycophenolate | Antimetabolites; autoimmune blistering disease, severe eczema | Marrow suppression, malignancy; mycophenolate teratogenic | TPMT before azathioprine; periodic blood count |
| Dapsone, apremilast and hydroxychloroquine | Dapsone: neutrophilic dermatoses; apremilast: PDE4 inhibitor; hydroxychloroquine: lupus | Dapsone: haemolysis and methaemoglobinaemia; apremilast: diarrhoea and mood; hydroxychloroquine: retina | G6PD before dapsone; periodic retinal screening; dose up to 5 mg/kg |
A free exam question
מטופל אשר נוטל AZATHIOPRINE מזה מספר שנים מקבל מרופא המשפחה שלו מרשם לתרופה חדשה. כעבור חודש ימים, מופנה למיון עקב דימום רקטלי. בבדיקה במיון, תרומבוציטים 20,000 . מה התרופה שנוספה? (the question as examined, in Hebrew)
- א. PROBENICID
- ב. PHENYTOIN
- ג. ACITRETIN
- ד. ALLOPURINOL
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Sources
- Joint AAD-NPF guidelines of care for the management of psoriasis with systemic nonbiologic therapies, 2020 — Methotrexate, ciclosporin, acitretin, apremilast
- British Association of Dermatologists guidelines for the safe and effective prescribing of methotrexate, 2016 — Monitoring
- American Academy of Ophthalmology recommendations on screening for hydroxychloroquine retinopathy, 2016 — Dosing and screening
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.