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Dermatology Medications Study Guide

Topical Corticosteroids

Potency Classification and Selection

Topical corticosteroids are classified into seven potency classes, with Class I being the most potent and Class VII the least potent, and selection depends critically on the anatomic site and disease severity. 1, 2

• Class I (Super-high potency): Clobetasol propionate 0.05%, halobetasol propionate, betamethasone dipropionate cream/ointment—reserved for thick-skinned areas (palms, soles) and severe disease 1
• Class V-VI (Low-medium potency): Hydrocortisone 2.5%, desonide, aclometasone—safe for facial use, intertriginous areas, and pediatric patients 1, 2
• Intermediate classes (II-IV): Used for trunk and extremities with moderate disease 3

Application Guidelines by Anatomic Site

For facial dermatitis, use only Class V-VI corticosteroids (hydrocortisone 2.5%, desonide, or aclometasone) applied twice daily to minimize risk of skin atrophy and telangiectasias. 1, 2

• Face and genitals: Class V-VI only due to thin skin and high absorption risk 1, 2
• Body/trunk: Class I-IV acceptable depending on severity 1
• Eyelids: Class VI-VII only—highest risk area for atrophy 4

Duration and Frequency

Super-high potency corticosteroids should be used for maximum 3 weeks, while low-potency agents can be used indefinitely with appropriate monitoring. 3

• Super-high potency (Class I): Maximum 3 weeks 3
• High-medium potency (Class II-IV): Up to 12 weeks 3
• Low potency (Class V-VII): No specified time limit 3
• Application frequency: Once or twice daily is equally effective for most conditions 3

Dosing: Fingertip Unit Method

One fingertip unit (FTU) covers approximately 2% body surface area in adults and is the standard measurement for prescribing quantities. 3

• 1 FTU = medication from fingertip to first joint crease 3
• Face and neck: 2.5 FTU 3
• One arm: 3 FTU 3
• One leg: 6 FTU 3
• Trunk (front or back): 7 FTU 3

Critical Safety Considerations

The risk of hypothalamic-pituitary-adrenal (HPA) axis suppression increases with potency, duration, occlusion, large surface area, and use on thin skin—particularly dangerous in children. 4, 3

• Avoid prolonged use of potent steroids on face, genitals, and flexures due to increased systemic absorption 4
• Children require lower potencies and shorter durations due to higher body surface area-to-weight ratio 3
• Pregnancy/lactation: Generally safe with appropriate potency selection 3
• Common adverse effects: Skin atrophy, striae, telangiectasias, rosacea, purpura, acneiform eruptions 3

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Topical Calcineurin Inhibitors

Indications and Advantages

Tacrolimus 0.1% and pimecrolimus 1% are steroid-sparing agents ideal for facial and intertriginous areas because they do not cause skin atrophy or HPA axis suppression even with long-term use. 2, 4

• Primary advantage: No atrophy risk, allowing safe long-term use on face and flexures 2, 4
• Minimal systemic absorption: Low blood concentrations even with extensive application 4
• Common side effect: Transient burning/stinging at application site 4

Clinical Application Strategy

Use mid-potency topical corticosteroids for acute flares, then transition to calcineurin inhibitors for maintenance therapy to minimize steroid exposure. 4

• Acute phase: Topical corticosteroid to rapidly control inflammation 4
• Maintenance phase: Switch to tacrolimus or pimecrolimus for long-term control 2, 4
• Facial dermatitis algorithm: Start hydrocortisone 2.5%, escalate to tacrolimus 0.1% if inadequate response or for long-term management 2

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Topical Antibiotics for Acne and Rosacea

Erythromycin

Erythromycin is available as monotherapy or combined with benzoyl peroxide, with the combination significantly more effective than vehicle for acne vulgaris. 1

• Dosing: Applied twice daily after washing 1
• Combination with benzoyl peroxide: Reduces antibiotic resistance risk 1
• Pregnancy category: B (monotherapy), C (with benzoyl peroxide) 1
• Key adverse effect: Pseudomembranous colitis (rare with topical use) 1

Clindamycin

Clindamycin 1% gel or solution applied once daily is effective for acne, but combination with benzoyl peroxide is preferred to prevent resistance. 1

• Monotherapy dosing: Once daily application 1
• Combination with benzoyl peroxide: Once daily in evening, more effective than either agent alone 1
• Contraindication: History of antibiotic-associated colitis or regional enteritis 1
• Pregnancy category: B (monotherapy), C (with benzoyl peroxide) 1

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Oral Antibiotics for Dermatologic Conditions

Tetracyclines for Acne and Rosacea

Doxycycline 100 mg twice daily or minocycline 50 mg twice daily for at least 6 weeks is first-line oral antibiotic therapy for moderate-to-severe acne and papulopustular rosacea. 1

• Doxycycline: 100 mg twice daily 1
• Minocycline: 50 mg twice daily 1
• Oxytetracycline: 500 mg twice daily 1
• Duration: Minimum 6 weeks for acne 1
• Anti-inflammatory mechanism: Efficacy beyond antimicrobial effect 1

Tetracyclines for Bullous Pemphigoid

Tetracyclines combined with nicotinamide (500-2500 mg daily) are second-line therapy for bullous pemphigoid, particularly in patients with diabetes or hypertension where systemic steroids pose higher risk. 1

• Indication: Localized/mild bullous pemphigoid or as steroid-sparing agent 1
• Dosing options: Doxycycline 200 mg/day, oxytetracycline 1 g/day, lymecycline 408 mg twice daily, minocycline 100 mg/day 1
• Combination: Often used with nicotinamide for enhanced efficacy 1

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Systemic Corticosteroids

Bullous Pemphigoid Protocol

For moderate-to-severe bullous pemphigoid, oral prednisone 0.5-1.0 mg/kg/day is first-line therapy, with mandatory taper once disease control is achieved. 1

• Localized/mild disease: 0.3 mg/kg/day 1
• Moderate-to-severe disease: 0.5-1.0 mg/kg/day 1
• Taper protocol: Reduce dose once control achieved, typically over 4-6 weeks 1
• Maintenance: Continue for 8-12 months total duration 1

Drug-Induced Rash Management

For grade 3 papulopustular rash from EGFR inhibitors, interrupt the causative agent and administer prednisone 0.5-1 mg/kg/day for 7 days with taper over 4-6 weeks. 1

• Grade 1-2 rash: Continue drug, use topical steroids and oral antibiotics 1
• Grade 3 rash: Hold drug, prednisone 0.5-1 mg/kg for 7 days, taper over 4-6 weeks 1
• Restart criteria: Resume drug when rash improves to grade 1 1

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Retinoids

Tretinoin (Topical)

Tretinoin cream (0.025%, 0.05%, 0.1%) or gel (0.01%, 0.025%) applied once daily at bedtime is FDA-approved for acne vulgaris treatment. 5

• Application: Thin layer once daily before bedtime 1, 5
• Avoid: Eyes, mouth, nasal creases, mucous membranes 1
• Vehicle selection: Gel for oily skin, cream for dry skin 5
• Pregnancy category: C—contraindicated in pregnancy 1

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Antihistamines for Pruritus

Dosing Recommendations

For dermatologic pruritus, use cetirizine or loratadine 10 mg daily (non-sedating) or hydroxyzine 10-25 mg four times daily or at bedtime (sedating). 1

• Non-sedating options: Cetirizine 10 mg daily, loratadine 10 mg daily 1
• Sedating option: Hydroxyzine 10-25 mg QID or at bedtime 1
• Severe pruritus: Consider GABA agonists (gabapentin 100-300 mg TID, pregabalin) for grade 3 pruritus 1

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Emollients and Barrier Repair

Application Strategy

Apply fragrance-free, urea-containing (5-10%) or glycerin-based emollients at least twice daily to all affected areas to restore skin barrier function. 1, 2

• Frequency: Minimum twice daily, more often for severe xerosis 1, 2
• Formulation: Cream or ointment-based, fragrance-free 1, 2
• Active ingredients: Urea 5-10% or glycerin for enhanced barrier restoration 1, 2
• Timing: Apply immediately after bathing to lock in moisture 2