Medicine for acne: Tretinoin

Tretinoin
Tretinoin (Retin-A), also known as retinoic acid, is the agent of choice for noninflammatory acne consisting of open and closed comedones. It is available in various preparations: Retin-A solution (0.05%) is the strongest and most irritating. Retin-A gel (0.025% and 0.01%) is drying and is for oily skin. Retin-A cream (0.1%, 0.05%, and 0.025%) is lubricating and is for dry skin

Mechanism of action
Tretinoin, an oxidation product of vitamin A, initiates increased cell turnover in both normal follicles and comedones and reduces the cohesion between keratinized cells. It acts specifically on microcomedones (the precursor lesion of all forms of acne), causing fragmentation and expulsion of the microplug, expulsion of comedones, and conversion of closed comedones to open comedones. New comedone formation is prevented by continued use. Inflammation may occur during this process, temporarily making acne worse. Continual topical application leads to thinning of the stratum corneum, making the skin more susceptible to sunburn; sun damage; and irritation from wind, cold, or dryness. Irritants such as astringents, alcohol, and acne soaps will not be tolerated as they were previously. The incidence of contact allergy is very low. Because of the direct action of tretinoin on the microcomedone, many clinicians believe tretinoin is appropriate for all forms of acne

Combination therapy: synergism
Tretinoin enhances the penetration of other topical agents such as topical antibiotics and benzoyl peroxide. The enhanced penetration results in a synergistic effect with greater overall drug efficacy and a faster response to treatment

Application techniques
The skin should be washed gently with a mild soap (e.g., Purpose, Basis) no more than two to three times each day, using the hands rather than a washcloth. Special acne or abrasive soaps should be avoided. To minimize possible irritation, the skin should be allowed to dry completely by waiting 20 to 30 minutes before applying tretinoin. Tretinoin is applied in a thin layer once daily. Medication is applied to the entire area, not just to individual lesions. An amount the size of a pea is enough for a full facial application. Patients with sensitive skin or those living in cold, dry climates may start with an application every other or every third day. The frequency of application can be gradually increased to as often as twice each day if tolerated. The corners of the nose, the mouth, and the eyes should be avoided; these areas are the most sensitive and the most easily irritated. Tretinoin is applied to the chin less frequently during the initial stages of therapy; the chin is sensitive and is usually the first area to become red and scaly. Sunscreens should be worn during the summer months if exposure is anticipated.

Response to treatment

One to four weeks
During the first few weeks, patients may experience redness, burning, or peeling. Those with excessive irritation should use less frequent applications (i.e., every other or every third day.) Most patients adapt to treatment within 4 weeks and return to daily applications. Those tolerating daily applications may be advanced to a higher dosage or to the more potent solution.

Three to six weeks
New papules and pustules may appear because comedones become irritated during the process of being dislodged. Patients unaware of this phenomenon may discontinue treatment. Some patients never get worse and sometimes begin to improve dramatically by the fifth or sixth week

After six weeks
Most patients improve by the ninth to twelfth week and exhibit continuous improvement thereafter. Some patients never adapt to tretinoin and experience continuous irritation or continue to worsen. An alternate treatment should be selected if adaptation has not occurred by 6 to 8 weeks. Some patients adapt but never improve. Tretinoin may be continued for months to prevent appearance of new lesions