Treatment of Psoriatic Rashes
For chronic plaque psoriasis, initiate treatment with high-potency topical corticosteroids (clobetasol propionate 0.05% or betamethasone dipropionate 0.05%) combined with calcipotriene twice daily for 2-4 weeks, which achieves 58-92% clearance rates in mild disease. 1, 2
Initial Assessment and Severity Classification
Before prescribing, assess two critical components:
- Patient's perception of disability and functional impairment 3
- Objective body surface area (BSA) involvement using body mapping or PASI scoring 3, 1
Severity definitions:
- Mild disease: BSA ≤10% AND PASI ≤10 AND DLQI ≤10 4
- Moderate-to-severe disease: BSA >10% OR PASI >10 AND DLQI >10 4
- High-impact sites (face, scalp, palms, soles, flexures, genitals, nails) with functional impairment are classified as severe regardless of BSA or PASI 4
Critical pitfall: Screen for medications that worsen psoriasis before initiating treatment—beta-blockers, NSAIDs, lithium, chloroquine, and mepacrine can cause severe, potentially fatal deterioration. 3, 1, 2
Topical Therapy Algorithm for Mild Disease
First-Line Topical Regimen
Body plaques:
- Apply clobetasol propionate 0.05% or betamethasone dipropionate 0.05% twice daily for maximum 2-4 weeks 1, 2
- Combine with calcipotriene (vitamin D analog) for synergistic effect superior to either agent alone 1, 2
- Fixed-combination products (calcipotriene/betamethasone dipropionate gel or foam) provide convenient once-daily application 2
Scalp involvement:
- Use clobetasol propionate 0.05% shampoo twice weekly for rapid symptom relief within 3-4 weeks 2
Sensitive areas (face, genitals, intertriginous areas):
- Apply low-potency corticosteroids or topical calcineurin inhibitors to minimize atrophy risk 2
Mandatory Safety Monitoring for Topical Corticosteroids
- Regular clinical review every 4 weeks with no unsupervised repeat prescriptions 3, 2
- Limit moderate-potency preparations to maximum 100g per month 3, 2
- Require dermatological supervision for very potent (grade I) or potent (grade II) preparations 3, 2
- Implement treatment-free periods each year when alternative treatments are employed 3, 4
Alternative Topical Agents When First-Line Fails
Important principle: Patients who fail one topical agent may respond to another—trial alternatives before escalating to systemic therapy. 3, 4
Coal tar:
- Start with 0.5-1.0% crude coal tar in petroleum jelly, increase concentration every few days to maximum 10% 3, 4
- Crude extracts are messier but more effective than refined products 3
Dithranol (anthralin):
- Start at 0.1-0.25% concentration, increase in doubling concentrations as tolerated 3
- Use short contact mode (15-45 minutes every 24 hours) to minimize irritancy and staining 3
- Exercise great care on face, flexures, and genitalia 3
Tazarotene:
- Combine with moderate-to-high potency corticosteroids for body plaques to reduce irritation while enhancing efficacy 1, 2
Systemic Therapy for Moderate-to-Severe Disease
Escalation Triggers
Escalate to systemic therapy when:
- BSA involvement exceeds 5% 2
- Inadequate response to optimized topical therapy after 8 weeks 2
- Signs of erythrodermic or pustular psoriasis develop 2
- Disease relapses to >50% of baseline severity within 3 months after a treatment course 4
First-Line Systemic Option: Phototherapy
Narrowband UVB or PUVA is the least toxic systemic agent and should be considered first-line systemic treatment. 3, 2, 4
PUVA dosing protocol:
- Start at 70% of minimum phototoxic dose 3, 2, 4
- Increase successive doses by 40% if no erythema, by 20% if slight erythema, hold if more than slight erythema 3, 4
- Treatments given no more frequently than every 48 hours 3
- Typical course duration: 8-10 weeks 3, 4
Critical warning: Commercial sunbeds (ultraviolet A) are rarely effective and may cause premature skin aging and increased skin fragility—their use is not recommended. 3
Conventional Systemic Agents
When phototherapy is insufficient or contraindicated:
Methotrexate:
- Response time: 2 weeks 2, 4
- Absolute contraindications: pregnancy, breastfeeding, wish to father children, significant hepatic damage, anemia, leucopenia, thrombocytopenia 2, 4
Cyclosporin:
- Response time: 3 weeks 2
- Contraindicated with abnormal renal function, uncontrolled hypertension, or malignancy 2
Acitretin:
- Response time: 6 weeks 2
- Requires contraception with absolute contraindication for pregnancy or wish to conceive within 2 years of stopping 2
Biologic Therapy Selection
Escalate to biologics when both methotrexate and cyclosporine have failed, are not tolerated, or are contraindicated AND the patient's DLQI >10. 4
First-line biologic options for adults:
| Biologic | Dosing | Dose Escalation | Response Assessment |
|---|---|---|---|
| Ustekinumab | 45mg (if <100kg) or 90mg (if ≥100kg) at weeks 0,4, then every 12 weeks [4] | Increase to 90mg every 12 weeks (<100kg) or 90mg every 8 weeks (≥100kg) [4] | 16-28 weeks [4] |
| Adalimumab | 80mg week 0, 40mg week 1, then 40mg every other week [4,5] | Increase to 40mg weekly [4] | 14-16 weeks [4] |
| Etanercept | 25mg twice weekly or 50mg once weekly for 24 weeks [4] | Intensify to 50mg twice weekly for ≤12 weeks [4] | 10-14 weeks [4] |
| Infliximab | 5mg/kg at weeks 0,2,6, then every 8 weeks [2,4] | Increase to 5mg/kg every 6 weeks [4] | 14-16 weeks [4] |
Important safety consideration for adalimumab: Screen for active or latent tuberculosis, hepatitis B, and fungal infections before initiating therapy. Increased risk of serious infections and malignancy, including lymphoma and hepatosplenic T-cell lymphoma in adolescents and young adults. 5
Continuation criteria: Maintain therapy when PASI reduction ≥75% from baseline. 4
Modification criteria: Switch or adjust therapy if PASI improvement <50% from baseline. In the "gray zone" (PASI ≥50% but <75%), continue if DLQI ≤5; modify if DLQI >5. 4
Special Considerations for Specific Psoriasis Variants
Guttate Psoriasis
Guttate psoriasis is self-limiting in most cases and commonly less tolerant of topical treatment. 3
- Use low concentrations of tar and dithranol 3
- Ultraviolet B radiation may be especially helpful 3
- Investigate for streptococcal infection; treat persistent infection with phenoxymethyl penicillin or erythromycin 3
- Repeated attacks after documented tonsillitis warrant referral for consideration of tonsillectomy 3
Localized Pustular Psoriasis of Palms and Soles
- Apply moderately potent topical corticosteroid (grade III) for symptom relief 3
- Topical coal tar and dithranol may provide some benefit 3
- Consider systemic etretinate for resistant cases 3
Generalized Pustular Psoriasis
Infliximab demonstrates rapid and often complete disease clearance for generalized pustular psoriasis and should be considered first-line biologic therapy, with standard dosing of 5mg/kg infused at weeks 0,2, and 6, then every 8 weeks thereafter. 2
- Initial management usually consists of hospital admission and systemic agents 3
- Consider acitretin as an alternative treatment option 2
Erythrodermic Psoriasis
- Initial management usually consists of hospital admission and systemic agents 3
Medications to Absolutely Avoid
NEVER prescribe systemic corticosteroids for psoriasis—they precipitate erythrodermic psoriasis, generalized pustular psoriasis, or very unstable disease upon discontinuation. 1, 2, 4
Other medications that cause severe, potentially fatal deterioration:
Medications that may worsen psoriasis in some patients:
Common Pitfalls and How to Avoid Them
Perceived "tachyphylaxis" to topical corticosteroids is usually poor patient adherence, not true receptor down-regulation. Address compliance issues before switching therapies. 1, 4
Failure of one topical agent does not predict failure of another. Trial alternative topical agents before escalating to systemic therapy. 3, 4
Do not combine salicylic acid with calcipotriene—acidic pH inactivates calcipotriene and reduces effectiveness. 2
When inadequate response to a second or later biologic occurs: