What is the recommended treatment regimen for an adult with psoriasis?

Treatment of Psoriasis in Adults

For moderate-to-severe plaque psoriasis in adults, methotrexate is recommended as first-line systemic therapy, with biologics (particularly anti-IL17 agents like bimekizumab or ixekizumab, or anti-IL23 agents like risankizumab) reserved for inadequate response or when psoriatic arthritis is present. 1, 2, 3

Treatment Algorithm by Disease Severity and Context

First-Line Systemic Treatment

Methotrexate is the recommended initial systemic agent for moderate-to-severe psoriasis 1, 3:

• Dosing: 7.5 to 25 mg weekly, given as single dose or divided over 24 hours 1
• Route: Oral or subcutaneous administration 1
• Monitoring: Liver function tests every 3-6 months; baseline and annual hepatic serology if risk factors present 1
• Adjunct: Always prescribe folic acid or folinic acid to reduce GI and hepatic adverse effects (but avoid excessive doses that may reduce efficacy) 1
• Combination: Can be combined with narrowband UVB phototherapy to enhance efficacy 1

Key contraindications: Pregnancy (wait 3 months after discontinuation before conception), cirrhosis, significant cytopenias, nursing 1

When to Escalate to Biologics

Move to biologic therapy when:

• Inadequate response to methotrexate
• Methotrexate contraindicated or not tolerated
• Concomitant psoriatic arthritis present
• Need for rapid disease control

Biologic Selection Hierarchy

The most effective biologics for achieving complete or near-complete skin clearance (PASI 90) are 4, 5:

1. Anti-IL17 agents (highest efficacy):

   • Bimekizumab (high-certainty evidence) 4
   • Ixekizumab (moderate-certainty evidence) 4
   • Secukinumab 2
   • Caution: Monitor for mucocutaneous candidiasis and inflammatory bowel disease 6

2. Anti-IL23 agents (high efficacy with longer dosing intervals):

   • Risankizumab (moderate-certainty evidence) 4
   • Guselkumab 2
   • Tildrakizumab 2
   • Advantage: Durable responses, dosing every 12 weeks 6

3. Anti-IL12/23 agent:

   • Ustekinumab 2
   • Dosing: 45 mg if ≤100 kg, 90 mg if >100 kg, at weeks 0,4, then every 12 weeks 2
   • Can increase to 90 mg for all weights or every 8 weeks if inadequate response 2

4. Anti-TNF agents (established safety profile):

   • Infliximab (moderate-certainty evidence, most effective TNF inhibitor) 4
   • Adalimumab 2
   • Etanercept: 50 mg twice weekly for 12 weeks, then 50 mg weekly maintenance 2
   • Preferred when: Psoriatic arthritis present or cardiovascular risk factors 2, 3

Special Clinical Scenarios

Psoriatic Arthritis: TNF inhibitors remain preferred due to established efficacy for both skin and joint disease 1, 2. Ustekinumab also recommended (strength A) 2.

Nail Psoriasis: Ustekinumab, etanercept, or anti-IL17/IL23 agents 2

Scalp Psoriasis: Etanercept (strength A), ustekinumab, or anti-IL17/IL23 agents 2

Palmoplantar/Pustular/Erythrodermic: Consider cyclosporin for acute control 3, or ustekinumab 2

Cardiovascular Comorbidities: TNF inhibitors preferred 3

Comparative Efficacy Evidence

The network meta-analysis demonstrates clear hierarchy 4, 5:

• Anti-IL17 and anti-IL23 agents superior to anti-TNF agents and ustekinumab
• Bimekizumab, ixekizumab, and risankizumab showed evidence of superiority over secukinumab, brodalumab, and guselkumab
• Methotrexate less effective than adalimumab and infliximab 1
• No significant difference in serious adverse events between any intervention and placebo, though this is based on low event numbers and low-to-moderate certainty evidence 4, 5

Critical Monitoring and Safety Considerations

Methotrexate-specific:

• Test dose recommended, especially with impaired kidney function 1
• Hepatotoxicity risk increases with alcohol use, obesity, diabetes 1
• Consider GI/hepatology referral or transient elastography if abnormal liver tests or risk factors 1

All biologics:

• Screen for tuberculosis, hepatitis B, and consider baseline complete blood count before initiation
• The safety evidence is limited to 8-24 weeks in most trials; long-term safety requires ongoing surveillance 4, 5

Common Pitfalls

• Underutilizing methotrexate first-line: Despite lower PASI 90 rates than biologics, methotrexate remains guideline-recommended first-line therapy due to cost-effectiveness and established safety profile 1, 3
• Not prescribing folic acid with methotrexate: This significantly reduces adverse effects 1
• Inadequate monitoring: Methotrexate requires regular liver function monitoring 1
• Ignoring psoriatic arthritis: TNF inhibitors have superior evidence for joint involvement 1, 2