A topical combination preparation used primarily in the management of chronic plaque psoriasis, seborrheic dermatitis, and other hyperkeratotic or scaling dermatoses. Coal Tar (1% w/v) acts as an antipsoriatic and antipruritic agent by reducing epidermal proliferation and inflammation. Salicylic Acid (3% w/v) is a keratolytic agent that promotes desquamation of hyperkeratotic skin, enhances penetration of coal tar, and has mild anti-inflammatory properties. This combination is a cornerstone of topical therapy in India due to its efficacy, low cost, and long-standing safety profile.
Adult: Apply a thin layer to affected areas once or twice daily, or as directed by physician. For scalp: Apply to wet scalp, massage gently, leave on for 5-10 minutes, then rinse thoroughly.
Note: 1. Wash and dry the affected area. 2. Apply a thin film and rub gently until absorbed. 3. Avoid contact with eyes, mucous membranes, and genital areas. 4. For scalp use, part hair and apply directly to lesions. 5. Can be used under occlusion (e.g., plastic wrap) only under medical supervision for short periods to enhance efficacy on thick plaques. 6. Wash hands thoroughly after application.
The combination works synergistically. Salicylic Acid disrupts intercellular keratinocyte cohesion in the stratum corneum by dissolving the intercellular cement, leading to desquamation of scales. This keratolytic action allows for better penetration of Coal Tar into the psoriatic plaque. Coal Tar exerts antiproliferative effects by inhibiting DNA synthesis and reducing mitotic activity in the basal layer of the epidermis. It also has anti-inflammatory properties (reduces dermal infiltrate and epidermal neutrophils) and antipruritic effects, possibly via local vasoconstriction and a mild anesthetic action.
Pregnancy: Category C (US FDA). Animal reproduction studies not conducted. Coal tar may be absorbed and contains potential mutagens. Salicylic acid is absorbed and related to aspirin. Use only if potential benefit justifies potential fetal risk. Avoid use on large areas, for prolonged periods, or under occlusion. Preferable to use in second or third trimester if necessary, under dermatologist supervision.
Driving: No known effects on driving ability.
| Other Topical Salicylates or Keratolytics (e.g., Lactic Acid, Urea) | Increased risk of skin irritation and systemic absorption of salicylates. | Moderate |
| Topical Corticosteroids | Salicylic acid may enhance penetration of steroids, increasing potency and potential for side effects. | Moderate |
| Topical Tretinoin or Retinoids | Concomitant use can cause severe local irritation and dryness. | Major |
| Photosensitizing Drugs (e.g., Tetracyclines, Fluoroquinolones, Thiazides) | Coal tar is photosensitizing; additive risk of severe sunburn/phototoxicity. | Major |
| Oral Anticoagulants (e.g., Warfarin) | Absorbed salicylic acid may potentiate anticoagulant effect by displacing warfarin from protein binding sites and inhibiting platelet function. | Major (with large surface area application) |
| Oral Hypoglycemics (e.g., Sulfonylureas) | Salicylates may potentiate hypoglycemic effect. | Moderate (with large surface area application) |
| Methotrexate | Salicylates can reduce renal clearance of methotrexate, increasing risk of toxicity. | Major (with large surface area application) |