Sunscreen
“The first line of defense against UV damage and cancers of skin: A Pharmacological Overview”
Category: Topical photoprotective agents
Purpose: Prevent UV-induced skin damage, including Sunburn, Photoaging, Actinic keratosis, Skin cancers (Melanoma,
Squamous cell carcinoma, Basal cell carcinoma.
| Type | Examples | Mode of Action |
|---|---|---|
| Chemical sunscreens | Oxybenzone, Avobenzone, Octinoxate, Octocrylene | Absorb UVA/UVB and/or convert into harmless heat |
| Physical sunscreens Zinc oxide, Titanium dioxide | Physical sunscreens Zinc oxide, Titanium dioxide | Physical sunscreens Zinc oxide, Titanium dioxide |
Pharmacokinetics
- Topical absorption: Minimal for physical sunscreens; chemical agents like oxybenzone can be systemically absorbed in trace amounts.
- Metabolism: Applied Locally in the skin; systemic metabolism rare
- Elimination: Not clinically significant
Indications
Prevention of sunburn (acute UV damage), photo-ageing (wrinkles, hyperpigmentation), photosensitive reactions (Amiodarone induced blue man syndrome, autoimmune), skin cancers (especially in high-risk patients), post-procedure care (laser, chemical peels)
Chronic conditions like Melasma, lupus, albinism, vitiligo
Contraindications
Know hypersensitivity to any sunscreen ingredient (e.g., oxybenzone allergy)
Severe acne or open wounds in the application area (use physical blockers cautiously)
Infants <6 months – avoid sunscreen; use protective clothing instead.
Allergy information
| Reaction | Agent | Notes |
|---|---|---|
| Allergic contact dermatitis | Oxybenzone, Avobenzone | Most common in chemical sunscreens |
| Irritant dermatitis | Fragrances, preservatives | Use hypoallergenic formulas |
| Photo allergy / Photosensitivity | Para-aminobenzoic acid (PABA) | Now rarely used |
| Acneiform eruptions | Occlusive bases | Recommend non-comedogenic formulations |
Amiodarone induced Photo-sensitivity reaction
Mechanism: Amiodarone and its metabolites, possibly along with lipofuscin, accumulates within the skin’s deeper layers; upon UV exposure, they generate reactive oxygen species, damaging cellular components like DNA, cell membranes, and lipids, leading to cell injury and inflammation. Prolonged amiodarone use can lead to a blue-gray discoloration of the skin, especially in sun-exposed areas.
Type of reaction: Mostly phototoxic (immediate sunburn-like reaction), but chronic use may also cause photoallergic dermatitis.
Clinical features: Erythema, burning, and exaggerated sunburn on sun-exposed areas; long-term use can cause blue- gray skin hyperpigmentation.
Risk factors: High cumulative dose, prolonged therapy (usually after months), fair skin, and frequent sun exposure.
Prevention & management: Use broad-spectrum sunscreen (SPF ≥50), wear protective clothing, limit direct sun exposure; if severe, consider dose reduction or discontinuation according to physician advice.
Clinical Pharmacist recommendations
Assess skin type (Fitzpatrick scale) for SPF recommendation
Check for drug-induced photosensitivity (e.g., tetracyclines, thiazides)
Guide selection:
- Dry skin – Use cream/lotion
- Oily/acne-prone – Gel or fluid
- Children/sensitive skin – Physical blocker preferred
- Formulation review: Avoid alcohol-based or fragranced products in eczema/rosacea.
