ADAPALENE
Clinical safety rating: avoid
Contraindicated (not allowed)
Retinoic acid receptor agonist; binds to RARβ/γ nuclear receptors, modulating gene expression to normalize follicular keratinization and reduce comedogenesis.
| Metabolism | Hepatic metabolism via CYP2B6, CYP2C9, CYP3A4; also glucuronidation and oxidation pathways. |
| Excretion | Adapalene is eliminated primarily via biliary excretion into feces. After oral administration in animals, approximately 80% of the dose is recovered in feces and about 10% in urine; for topical application, systemic absorption is minimal and the small absorbed fraction undergoes similar hepatobiliary elimination. |
| Half-life | The terminal elimination half-life of adapalene after topical application is approximately 17 hours (range 7–51 hours), reflecting slow release from skin depot and hepatic clearance. This supports once-daily dosing. |
| Protein binding | Adapalene is highly protein-bound (>99%), primarily to albumin and lipoproteins, in human plasma. |
| Volume of Distribution | After intravenous administration in animals, the volume of distribution is approximately 1.4 L/kg, suggesting extensive tissue distribution. In humans, following topical application, the apparent Vd is not readily calculable due to low systemic absorption. |
| Bioavailability | Topical bioavailability of adapalene is extremely low (less than 1% of applied dose is absorbed systemically based on plasma concentration measurements). Oral bioavailability in humans is negligible as adapalene is not administered orally. |
| Onset of Action | For topical acne treatment: clinical improvement is typically observed after 4–8 weeks of once-daily application; visible reduction in inflammatory and non-inflammatory lesions begins around week 4. |
| Duration of Action | The pharmacodynamic effect persists with continued daily application. After discontinuation, therapeutic benefit gradually wanes over several weeks; no prolonged duration beyond dosing interval is expected. |
Apply a pea-sized amount topically to affected areas once daily in the evening.
| Dosage form | GEL |
| Renal impairment | No dose adjustment required; negligible systemic absorption. |
| Liver impairment | No dose adjustment required; not metabolized hepatically. |
| Pediatric use | Approved for acne vulgaris in children ≥9 years: apply a pea-sized amount topically once daily. |
| Geriatric use | No specific dose adjustment; use with caution due to increased skin fragility. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
No major systemic drug interactions due to minimal absorption Use of abrasive soaps or cosmetics may cause significant irritation Avoid excessive sun exposure.
| Breastfeeding | Unknown if adapalene is excreted in human milk. Minimal systemic absorption suggests low excretion. M/P ratio not available. Caution advised; avoid nursing area contact. Benefits vs risks should be considered. |
| Teratogenic Risk | Pregnancy Category C. Oral retinoids are teratogenic; topical adapalene has minimal systemic absorption (<0.1% of applied dose). No adequate studies in pregnant women. First trimester: theoretical risk of retinoid embryopathy (craniofacial, cardiac, CNS defects). Second/third trimesters: risks considered low due to negligible systemic exposure. Avoid use unless clearly needed. |
■ FDA Black Box Warning
No FDA boxed warning.
| Common Effects | Skin rash Vomiting Dizziness General discomfort Headache |
| Serious Effects |
["Hypersensitivity to adapalene or any component","Pre-existing severe eczema or sunburn"]
| Precautions | ["Photosensitivity may occur; minimize sun/UV exposure.","Local irritation (erythema, peeling, dryness) common; consider lower concentration or dosing frequency.","Pregnancy: Teratogenic in animal studies; avoid use in pregnant women (Category C)."] |
| Food/Dietary | No significant food interactions. Avoid topical application with fatty foods or oils on skin as they may increase absorption. |
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| Fetal Monitoring | No specific monitoring required beyond usual prenatal care. If accidental high-dose oral exposure, fetal ultrasound for anomalies. |
| Fertility Effects | No known effects on fertility in animal studies. Topical use unlikely to impact reproductive function due to low absorption. |
| Clinical Pearls | Adapalene is a third-generation topical retinoid with anti-inflammatory properties. It is less irritating than tretinoin and is FDA-approved for acne vulgaris. It works by normalizing follicular keratinization and reducing comedone formation. Onset of therapeutic effect is typically 8-12 weeks. Combination with benzoyl peroxide or clindamycin may enhance efficacy. Avoid concurrent use of other topical retinoids. Use with caution in patients with eczema or sunburn. |
| Patient Advice | Apply a pea-sized amount to clean, dry skin once daily in the evening. · Avoid applying to broken, eczematous, or sunburned skin. · Use sunscreen daily as adapalene increases photosensitivity. · May cause initial dryness, peeling, or redness; use moisturizer as needed. · Therapeutic effect may not be seen for 8-12 weeks; do not discontinue prematurely. · Do not use if pregnant, planning to become pregnant, or breastfeeding. |