Dermatological agents

Dermatological agents are medications formulated for application to the skin, mucous membranes, hair, or nails for the purpose of treating, preventing, or diagnosing dermatologic conditions. These agents span a wide pharmacologic spectrum and are essential in managing various skin-related pathologies including infections (bacterial, fungal, viral), inflammatory disorders (eczema, psoriasis), neoplastic conditions (actinic keratoses, skin cancers), pigmentary issues (melasma, vitiligo), and cosmetic concerns (wrinkles, acne scars). Given that the skin is the body's largest organ and the first barrier against environmental aggression, effective dermatological treatment is essential not only for aesthetic improvement but also for functional restoration and prevention of complications.

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1. Classifications of Dermatological Agents

Dermatological agents are categorized based on their pharmacological action and clinical indication:

• Topical anti-infectives

• Topical corticosteroids and steroid combinations

• Topical anti-inflammatory agents (non-steroidal)

• Topical antifungals, antibiotics, antivirals, antiparasitics

• Keratolytics and retinoids

• Antipsoriatics

• Antineoplastics

• Emollients, moisturizers, and barrier repair agents

• Depigmenting agents and photochemotherapeutics

• Acne treatment agents

• Astringents and protectants

• Rubefacients and counterirritants

• Anesthetics and analgesics

• Cosmeceuticals (vitamin C, peptides, antioxidants, exfoliants)

Each class may be delivered via creams, ointments, gels, foams, lotions, emulsions, patches, or sprays, depending on the target area and drug properties.

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2. Routes and Formulations

Topical delivery enhances drug concentration at the site of action while minimizing systemic absorption. Formulation choice depends on the location, extent, and nature of the skin lesion.

• Creams (oil-in-water): Cosmetically elegant, suitable for moist lesions and intertriginous areas.

• Ointments (water-in-oil): Occlusive, suitable for dry and scaly lesions, avoid on weeping dermatitis.

• Gels: Alcohol-based or aqueous, preferred for oily skin or scalp.

• Lotions: For hairy areas or large surface areas.

• Solutions: Useful on the scalp and hairy regions.

• Foams: Rapid absorption and even distribution; good for scalp.

• Patches: Used for sustained drug release in localized conditions.

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3. Topical Anti-Infectives

These agents are used to treat or prevent infections caused by bacteria, fungi, viruses, or parasites.

• Topical antibiotics: Mupirocin, fusidic acid, neomycin, bacitracin—used in impetigo, minor wounds, folliculitis.

• Topical antifungals: Clotrimazole, terbinafine, ketoconazole—for tinea infections, candidiasis.

• Topical antivirals: Acyclovir, penciclovir—for herpes labialis, genital herpes.

• Topical antiparasitics: Permethrin, ivermectin—treatment of lice, scabies, and rosacea.

These drugs are usually well tolerated. However, prolonged use may lead to local irritation, contact dermatitis, or microbial resistance.

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4. Topical Corticosteroids

Topical corticosteroids are the cornerstone of anti-inflammatory treatment in dermatology. They act via glucocorticoid receptors to inhibit pro-inflammatory gene expression.

Potency Classification (UK and US system):

• Mild: Hydrocortisone 1%

• Moderate: Clobetasone butyrate

• Potent: Betamethasone valerate 0.1%

• Very potent: Clobetasol propionate 0.05%

Indications:

• Eczema, psoriasis, lichen planus, seborrheic dermatitis, contact dermatitis

Risks with overuse:

• Skin atrophy

• Striae

• Perioral dermatitis

• Tachyphylaxis

• Systemic absorption (especially in children)

Steroid stewardship is essential—potent steroids should not be used on face, groin, or under occlusion for extended periods.

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5. Topical Calcineurin Inhibitors

Non-steroidal anti-inflammatory agents such as tacrolimus and pimecrolimus are used as steroid-sparing treatments.

Mechanism:
Inhibit T-cell activation via calcineurin pathway

Uses:

• Atopic dermatitis

• Vitiligo

• Lichen planus (off-label)

Advantages include reduced risk of atrophy, making them suitable for long-term use on sensitive areas.

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6. Topical Retinoids and Keratolytics

Retinoids normalize keratinization, reduce inflammation, and promote dermal collagen synthesis.

• Examples: Tretinoin, adapalene, tazarotene

• Uses: Acne vulgaris, photoaging, psoriasis, hyperpigmentation

Keratolytics such as salicylic acid and urea are used to:

• Break down hyperkeratosis

• Enhance penetration of other agents

Side effects include erythema, peeling, photosensitivity, and irritation.

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7. Topical Antipsoriatics

These agents help manage plaque psoriasis, targeting hyperproliferation and inflammation.

• Vitamin D analogs: Calcipotriol, calcitriol

• Coal tar: Anti-proliferative and anti-inflammatory

• Dithranol (anthralin): Effective but irritating and staining

• Combination therapy: Calcipotriol + betamethasone

These are used in chronic plaque-type psoriasis and often combined with phototherapy or systemic agents.

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8. Topical Antineoplastics

Used to treat precancerous lesions and superficial skin cancers.

• 5-Fluorouracil (5-FU): Inhibits thymidylate synthase → treats actinic keratosis, superficial BCC

• Imiquimod: Toll-like receptor agonist inducing local cytokine release

• Ingenol mebutate: Cytotoxic and immunomodulatory

• Diclofenac: Used in actinic keratosis

Side effects are usually inflammatory reactions—erythema, crusting, ulceration.

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9. Acne Therapy Agents

Topical acne treatments target comedogenesis, bacterial proliferation, and inflammation.

• Benzoyl peroxide: Antimicrobial, keratolytic

• Topical antibiotics: Clindamycin, erythromycin (combine with BPO to prevent resistance)

• Retinoids: Tretinoin, adapalene

• Azelaic acid: Antimicrobial and anti-keratinizing

Combination therapies are often used and tailored to acne severity.

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10. Emollients, Moisturizers, Barrier Agents

These agents restore and maintain the skin barrier.

• Occlusives: Petrolatum, lanolin

• Humectants: Glycerin, urea, lactic acid

• Barrier creams: Dimethicone, zinc oxide

Indicated in eczema, ichthyosis, psoriasis, xerosis, and post-procedure skin care.

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11. Depigmenting and Lightening Agents

Used to treat hyperpigmentation disorders such as melasma, PIH.

• Hydroquinone: Tyrosinase inhibitor

• Azelaic acid: Also used for acne and rosacea

• Kojic acid, arbutin

• Tretinoin: Enhances penetration and skin turnover

Strict photoprotection is required during use to prevent rebound pigmentation.

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12. Photochemotherapeutics

Used in combination with UVA exposure.

• Psoralens (e.g., methoxsalen): Sensitize skin to UVA for PUVA therapy

• Used in psoriasis, vitiligo, cutaneous T-cell lymphoma

Requires controlled dosing and carries risk of phototoxicity, nausea, carcinogenesis.

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13. Local Anesthetics

Applied for pain relief, often used pre-dermatologic procedures.

• Examples: Lidocaine, prilocaine

• Forms: Creams, gels, patches

• EMLA (eutectic mixture of local anesthetics) used widely in pediatric and minor procedures

Systemic absorption may lead to toxicity if applied over large or broken skin areas.

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14. Astringents, Protectants, and Rubefacients

• Astringents: Aluminum acetate (Burrow’s solution), witch hazel—used to dry weeping skin lesions

• Protectants: Zinc oxide, calamine—create a physical barrier

• Rubefacients: Capsaicin, methyl salicylate—used in musculoskeletal pain for their counterirritant effects

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15. Risks, Contraindications, and Drug Interactions

• Hypersensitivity: Common with neomycin, preservatives, lanolin

• Photosensitivity: Retinoids, psoralens, benzoyl peroxide

• Systemic absorption: Potent steroids, anesthetics in infants or broken skin

• Drug interactions:

  • Topical antibiotics with systemic agents may promote resistance

  • Avoid simultaneous use of multiple irritants (e.g., retinoids and salicylic acid)

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16. Pediatric and Geriatric Considerations

• Pediatric skin is thinner and more permeable—risk of systemic effects higher

• Geriatric skin may require milder formulations due to atrophic changes and xerosis

• Tailoring therapy to skin integrity and underlying condition is essential

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17. Cosmetic Dermatological Agents (Cosmeceuticals)

• Vitamin C: Antioxidant, anti-aging

• Peptides: Promote collagen synthesis

• Niacinamide: Anti-inflammatory, depigmenting

• Alpha-hydroxy acids: Glycolic, lactic acids for exfoliation

• Ceramides: Skin barrier support

Although not regulated as drugs, these agents are widely used in adjunctive care and preventive dermatology.

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18. Role in Dermatological Conditions

Condition	Common Topical Therapies
Acne vulgaris	Retinoids, BPO, clindamycin
Psoriasis	Vitamin D analogs, corticosteroids, tazarotene
Eczema	Emollients, corticosteroids, calcineurin inhibitors
Tinea corporis	Azoles, terbinafine
Herpes simplex	Acyclovir
Actinic keratosis	5-FU, imiquimod
Melasma	Hydroquinone, tretinoin
Lichen planus	Topical corticosteroids
Seborrheic dermatitis	Ketoconazole, zinc pyrithione
Hyperkeratosis	Urea, salicylic acid

19. Regulatory and Safety Monitoring

• Topical agents are regulated as over-the-counter (OTC) or prescription (Rx) drugs

• Pharmacovigilance systems track adverse dermatologic events

• Counseling on proper application, sun protection, and treatment adherence is integral to safe use