How topical retinoid drugs can be used to treat acne

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Topical Retinoid Drugs in Acne Treatment

Retinoids are derived from retinoic acid, commonly called Vitamin A. They were first observed to be effective in curing acne in the 1970’s. Mild non-inflammatory acne, characterized by the presence of comedones is best treated by topical retinoids, whereas moderate acne can by treat with a combination of retinoids with systemic drugs.

Mechanism of action:

The basic clinical lesion the microcomedo, if left untreated can progress to inflammatory acne with pustules and residual scarring. Retinoids bind and activate retinoid receptors on cells. This leads to the control of the cell differentiation in the hair follicle and controls acne progression. The topical retinoid treatment should therefore not only be restricted to application on visible lesions, but the entire acne prone area to help prevent future spots.

Types: There are three generations of retinoids:

a) nonaromatics: such as retinol, tretinoin and isotretinoin
b) monoaromatic retinoids
c) polyaromatic retinoids: such as arotinoid, adapalene and tazatorene (these have anti-inflammatory efficacy)

Topical retinoids popularly used in effectively treating acne are tretinoin, isotretinoin, adapalane, tazarotene and retinaldehyde.

Tretinoin

Tretinoin is available in cream, gel and solution forms. It increases the formation of follicular epithelial cells and eliminates follicular epithelial cells thus preventing excess cellular debris and facilitating the drainage of comedone. This also helps prevent the formation of new comedones. The follicles become clear and more within the reach of antimicrobial agents. This in turn inhibits the P. acnes bacteria proliferation.

Side effects include skin irritation and flare ups of existing lesions along with photosensitivity, i.e. increased sensitivity of skin to sunlight. Night time application starting with a lower potency is advised. Patients with sensitive skin should avoid tretinoin, however nowadays two new formulations of tretinoin, namely the polyolpolymer-2 and the microsponge delivery system, are used for lower accompanying irritation.

Isotretinoin

This is a first generation retinoid which has comedolytic properties caused by changing the turnover of epithelial cells in hair follicles. It is available in gel and oral formulations. The gel form does not have the sebum suppressor effect of oral isotretinoin. Its effect in reducing both comedolytic as well as inflammatory acne is almost equal to tretinoin, with lesser side effect compared to tretinoin.

Adapalene

This is a third generation polyaromatic retinoid. It normalizes cellular keratinization and inflammation, thus it is extremely comedolytic as well as anti inflammatory. Adapalene is stable with oxygen and light so it can be applied at any time of the day and it can be combined with benzoyl proxide. Though as effective as tretinoin, it is much better tolerated and produces less skin irritation and erythema. There is negligible absorption of adapalene and once it goes into the corneum strata, it becomes enclosed in the targeted area of the epidermis and hail follicle.

Tazarotene

It has been seen that tazarotene when applied once a day has greater success in treating non inflammatory acne and reducing its severity compared to tretinoin. Also tazarotene gel .05% is more effective in lessening the number of open comedones and papules and reducing pustules faster than the same potency of tretinoin gel. However, it is as equally intolerable as tretinoin. Moderate skin irritation accompanied by burning and itching sensations, erythema, peeling and dryness is felt by some patients. So it is advised that tazarotene be applied for a very short period of time of 30 seconds to 5 minutes everyday for optimum results, but with a lower irritation level.

Retinaldehyde

This topical retinoid with .05% potency has an effect similar to that of tretinoin but with the added benefit of better tolerance It has a comedolytic effect and directly prevents the proliferation of P.acnes.

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