Topical Corticosteroid Potency Classification and Selection
Topical corticosteroids are classified into 7 potency classes (Class 1 being ultra-high potency to Classes 6-7 being low potency), and selection should be based on anatomic location, disease severity, and treatment duration, with Class 1 agents limited to 2-4 weeks and lower potency agents preferred for face, intertriginous areas, and pediatric patients. 1
Potency Classification System
The American Academy of Dermatology uses a 7-tier classification system based on vasoconstrictor assay potency 1, 2:
- Class 1 (Ultra-high/Superpotent): Clobetasol propionate 0.05%, halobetasol propionate 0.05% with efficacy rates of 58-92% 3, 1
- Class 2 (High potency): Amcinonide 0.1%, betamethasone dipropionate 0.05%, fluocinonide 0.05% with efficacy rates of 68-74% 3, 1
- Classes 3-4 (Medium potency): Efficacy rates of 68-72% 3, 1
- Classes 5-7 (Low potency): Hydrocortisone 1% and 2.5% with efficacy rates of 41-83% 3, 1
Selection Algorithm Based on Anatomic Location
Face, genitals, and intertriginous areas: Use only Classes 5-7 (low potency) due to increased percutaneous absorption and high risk of skin atrophy in these thin-skinned areas 3, 1, 2
Trunk and extremities with thick plaques: Class 1 (ultra-high potency) corticosteroids are appropriate for initial control 3, 1
Scalp psoriasis: All classes (1-7) can be used for up to 4 weeks 3, 1
Pediatric patients: Preferentially use Class 6 corticosteroids due to lower risk of systemic absorption and adrenal suppression 1, 4
Duration Guidelines by Potency Class
Class 1 (Ultra-high potency): Strictly limit to 2-4 weeks of continuous use 3, 1, 4
Classes 2-5 (High to medium potency): Can be used for up to 4 weeks for plaque psoriasis not involving intertriginous areas 3, 1
Classes 6-7 (Low potency): No specified time limit due to favorable safety profile, suitable for long-term maintenance therapy 1, 4
Application Strategy and Tapering
Apply topical corticosteroids as a thin film 1-2 times daily depending on severity 2, 4. For extensive disease requiring Class 1 agents like clobetasol propionate 0.05%, use 30-40 g per day initially (20 g if weight <45 kg) 3.
Tapering schedule after disease control (when new lesions cease and established lesions heal) 3:
- Month 1: Daily treatment
- Month 2: Every 2 days
- Month 3: Twice weekly
- Month 4 onward: Once weekly
After initial control with higher potency agents, transition to the lowest potency that maintains disease control to minimize long-term adverse effects 3, 1.
Critical Safety Considerations
Common adverse effects include skin atrophy, striae, telangiectasia, purpura, and folliculitis, with face and intertriginous areas at greatest risk 3, 4. These risks increase with prolonged use, higher potency, occlusion, and application to thin-skinned areas 4.
Avoid abrupt discontinuation of potent topical corticosteroids as rebound flares can occur, though frequency is variable 3.
Occlusive dressings substantially increase percutaneous absorption and should be discontinued if infection develops 2.
Quantity Prescribing Using Fingertip Units
One fingertip unit (from fingertip to first joint crease) covers approximately 2% body surface area in adults 4, 5. Approximately 400 g of topical agent is required to cover the entire body surface twice daily for 1 week in an average-sized adult 3.
Special Clinical Scenarios
For localized/mild disease: Very potent topical steroids applied to lesional skin only are first-line (Strength of Recommendation A) 3
For moderate-to-severe disease: Either systemic corticosteroids 0.5-1.0 mg/kg daily OR very potent topical steroids 5-15 g twice daily to whole skin surface if patient/carer is capable (Strength of Recommendation A) 3
Steroid-sparing approach: Consider calcineurin inhibitors (tacrolimus, pimecrolimus) for facial and intertriginous psoriasis as steroid-sparing agents for prolonged use beyond 4 weeks 3