Adapalene

Adverse reactions reported from adapalene include photosensitivity, irritation, redness, dryness, itching, and burning. These are usually mild adverse events.；Adapalene is less irritating compared to other topical retinoids. In a blinded, randomized, controlled, parallel-group study of 591 acne patients, a combined safety analysis conducted in the United States and Europe compared adapalene 0.1% gel and tretinoin 0.025% gel. The number of patients discontinuing the study due to adverse events was about twice as high in those using tretinoin (2.4%) compared to adapalene (1.3%). There were no systemic adverse reactions noted in the study. Most of the adverse reactions observed were related to skin irritation. Multiple other studies have demonstrated similar findings.；Adapalene 0.1% and 0.3% have also been compared to tazarotene in multiple studies showing adapalene to be non-inferior in efficacy and demonstrated superior tolerability. The enhanced tolerability of adapalene has been attributed, in part, to the selective affinity to the nuclear RAR-beta and RAR-gamma receptors, as opposed to RAR-alpha. The decreased risk of skin irritation may contribute to better long-term compliance. Exposure to ultraviolet light should be minimized in patients using adapalene gel. Patients exposed to high levels of sun exposure and sensitive to sunlight should exercise caution. Using sunscreen and protective clothing over adapalene-treated areas is suggested when patients cannot avoid exposure to the sunlight.；Rare, severe allergic reactions characteristically demonstrate pruritus, facial edema, lip swelling, and eyelid swelling. If a patient experiences anaphylactic reactions with symptoms, including facial swelling, hives, chest pain, or shortness of breath, adapalene should be discontinued, and the patient should seek immediate medical evaluation.

If the adapalene is applied excessively, marked redness, scaling, or skin discomfort may occur. In addition, according to product labeling, chronic ingestion of the drug may lead to the same adverse drug reactions associated with excessive oral intake of vitamin A.

Mechanistically, adapalene binds to specific retinoic acid nuclear receptors (gamma and beta) and retinoid X receptors but does not bind to the cytosolic receptor protein. Although the exact mode of action of adapalene is unknown, it is suggested that topical adapalene may normalize the differentiation of follicular epithelial cells resulting in decreased microcomedone formation.

◉ Summary of Use during Lactation；Topical adapalene has not been studied during breastfeeding. Because it is poorly absorbed after topical application, and blood levels are less than 0.25 mcg/L with long-term use, it is probably a low risk to the nursing infant. Absorption should be minimized by applying it to the smallest possible surface area of the body for the shortest time possible. Do not apply to the nipple area and ensure that the infant’s skin does not come into direct contact with the areas of skin that have been treated.；◉ Effects in Breastfed Infants；Relevant published information was not found as of the revision date.；◉ Effects on Lactation and Breastmilk；Relevant published information was not found as of the revision date.

Extensive information regarding adapalene metabolism in humans is unavailable, although it is known to accumulate in the liver and GI-tract. In human, mouse, rat, rabbit, and dog cultured hepatocytes, metabolism appears to affect the methoxybenzene moiety but remains incompletely characterized. The major products of metabolism are glucuronides. Approximately 25% of the drug is metabolized; the rest is excreted as parent drug.

Metabolized mainly by O-demethylation, hydroxylation and conjugation, and excretion is primarily by the biliary route. Route of Elimination: Excretion appears to be primarily by the biliary route.

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ADAPALENE

Established Pharmacologic Class [EPC] - Retinoid

Chemical Structure [CS] - Retinoids

Adapalene is a Retinoid.

ADAPALENE

Anti-inflammatory agents that are non-steroidal in nature. In addition to anti-inflammatory actions, they have analgesic, antipyretic, and platelet-inhibitory actions. They act by blocking the synthesis of prostaglandins by inhibiting cyclooxygenase, which converts arachidonic acid to cyclic endoperoxides, precursors of prostaglandins. Inhibition of prostaglandin synthesis accounts for their analgesic, antipyretic, and platelet-inhibitory actions; other mechanisms may contribute to their anti-inflammatory effects.

Drugs used to treat or prevent skin disorders or for the routine care of skin.

Adapalene is applied topically and absorbed through the skin. In one clinical study treating patients once per day with 2g of 0.3% gel applied to 2 mg/cm2 of skin, 15 patients had detectable blood plasma adapalene levels (0.1 ng/ml) resulting in a mean Cmax of 0.553 ± 0.466 ng/ml and a mean AUC of 8.37 ± 8.46 ng\*h/ml on day 10.

Adapalene is primarily excreted by the biliary route at about 30 ng/g of the topically applied amount. Approximately 75% of the drug remains unchanged.

Adapalene is rapidly cleared from blood plasma, typically undetectable after 72 hours following topical application.