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ChenDermatologist
ChenDermatologist
Dr. Chen Yi-Jia · Dermatology Notes
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Patient education · Psoriasis / Systemic Per AAD-NPF 2019/2020 + BAD 2020/2023 + UpToDate 2024 · Updated 2026-05-09

Systemic therapy for psoriasis
Phototherapy, oral systemics, biologics, NHI coverage

For moderate-to-severe psoriasis (BSA > 10%, PASI > 10, DLQI > 10) or topical-refractory disease, three modern options: (1) Phototherapy NB-UVB (first-line, PASI 75 ~62%), (2) Oral systemics — methotrexate, cyclosporine, acitretin, apremilast, deucravacitinib, (3) Biologics — IL-23 (risankizumab/Skyrizi, guselkumab/Tremfya) and IL-17 (ixekizumab/Taltz, bimekizumab/Bimzelx) reach PASI 90 in 70-85%. This article includes a detailed comparison chart for self-pay decision-making.

Note: Systemic therapy requires dermatology specialist evaluation including pre-treatment screening (LFT, renal, TB, HBV/HCV, HIV, CHF, malignancy history, pregnancy) and ongoing monitoring. Patient education only — does not replace in-person consultation.
Key Fact (Menter 2019, JAAD · Elmets 2019, JAAD · BAD 2023)

The biologic era made PASI 90/100 clearance achievable — historically, conventional treatment targets were only PASI 50–75. Network meta-analysis ranks 16-week PASI 90 (high to low):infliximab、bimekizumab、ixekizumab, risankizumab, guselkumab (all ≥ 70%), then secukinumab, brodalumab, adalimumab; lowest: etanercept, tildrakizumab, apremilast. But drug selection considers more than efficacy — comorbidities (PsA / IBD / cardiovascular / infection history), pregnancy plans, dosing frequency, and Taiwan NHI coverage.

When to step up to systemic therapy

BSA > 10%, PASI > 10, DLQI > 10; 6 months of inadequate topical control; refractory special-site disease; concurrent psoriatic arthritis; pustular or erythrodermic disease.

Phototherapy — first-line

NB-UVB (311 nm) 2–3 sessions/week for 8–12 weeks; PASI 75 ≈ 62%. Safe, can be used in pregnancy. PUVA (psoralen + UVA) — higher efficacy but cumulative SCC risk after > 200 sessions; not for pregnancy. 308 nm excimer for localized refractory plaques.

Oral systemic agents

Methotrexate 10–25 mg weekly + folate; PASI 75 ≈ 35–45%; LFT/CBC monitoring; teratogenic. Cyclosporine 2.5–5 mg/kg/day, ≤ 1 year; fastest onset; renal/BP/lipid AE. Acitretin 10–50 mg/day; teratogenic (3-year window in females); excellent for palmoplantar/pustular; potent with phototherapy. Apremilast 30 mg BID (PDE4i); modest efficacy, oral convenience. Deucravacitinib 6 mg/day (TYK2i); novel oral with biologic-like efficacy.

Biologics — four classes

  • TNF-α inhibitors: adalimumab, etanercept, infliximab, certolizumab pegol (no transplacental — preferred in pregnancy).
  • IL-17 inhibitors: secukinumab, ixekizumab, brodalumab, bimekizumab (highest PASI 90 ≈ 85%). Avoid in active IBD.
  • IL-23 inhibitors: guselkumab, risankizumab (every 12 weeks), tildrakizumab. Best safety, longest dosing intervals, IBD-friendly.
  • IL-12/23 inhibitor: ustekinumab. Older, safe long-term track record.

Network meta-analysis 16-week PASI 90 ranking: infliximab, bimekizumab, ixekizumab, risankizumab, guselkumab (all ≥ 70%), then secukinumab, brodalumab, adalimumab; lowest etanercept, tildrakizumab, apremilast.

Taiwan NHI biologic coverage

"10/10/10 rule": PASI ≥ 10, BSA ≥ 10%, DLQI ≥ 10, plus failure of two systemics for ≥ 3 months each. Re-approval every 6 months requires sustained PASI 50 response or treatment goal.

Treatment goals and switching

3-month PASI 75/IGA 0–1; ideal PASI 90 or complete clearance; BSA < 1%, DLQI ≤ 1. If goals not met by 12–16 weeks: check adherence, anti-drug antibodies, weight-based dosing; otherwise switch to another class (TNFi → IL-17i or IL-23i).

Bottom line

Moderate-to-severe psoriasis is now highly treatable. Phototherapy is the safe and economical first-line; methotrexate retains its role; biologics targeting IL-17 and IL-23 reach PASI 90+. Plan 6–12 months of treatment, monitor comorbidities, and don't stop abruptly (rebound risk).