Isotretinoin, a derivative of vitamin A is a pharmacologically unique agent indicated for patient with severe cystic acne unresponsive to conventional therapy. Various mechanisms of action have been proposed to explain the therapeutic effectiveness of isotretinoin. This drug inhibits sebum production, decreases sebaceous gland size, reduces the number of acnes within follicles, and normalizes the keratinization process. Significant clinical response to Isotretinoin generally occurs with doses ranging from 0.1 to 1.5 mg/kg/day. Since the frequency and severity of adverse reactions appears to be dosen-related, the use of lower Isotretinoin is favored. A less favorable clinical response and subsequent retreatment is often necessary, however, when the lowest dose is used. Doses between 0.5 to 1 mh/kg/day appear most optimal if given once or twice a day for 15 to 20 weeks. Patients may continue to clinically improve after treatment has ended, but if total cyst counts have been reduced by 70% two months after cessation of therapy, a second 15-week course of Isotretinoin may be instituted. Lasting remissions occur in up to 90% of uncomplicated cases after 20 weeks of therapy. Lesions on the back appear to respond more slowly and may require higher doses or more courses of treatment. The bioavailability of Isotretinoin is increased when taken with food.

Side effects with Isotretinoin are significant. Cheilitis (i.e., chapped, peeling lips) seems to affect more than 90% of patients using this drug. Facial skin desquamation secondary to Isotretinoin affects about 30% of patients and seems to be due to retinoid-induced loss of desmosomes and less cohesive outer epidermis. Noncomedogenic emollients or 1% hydrocortisone cream may be helpful in managing these particular adverse reactions.

Conjunctivitis and/or eye irritation (greater than 50% incidence) are manifested usually by dry eyes and inability to tolerate contact lenses. These adverse effects are possibly due to lower tear film stability from decreased sebaceous meibomian gland secretion. Corneal opacities and decreased night vision have also been reported in patients taking Isotretinoin for cystic acne. Patients who have dry eyes before therapy and those who use contact lenses should be cautioned in advance tat eye dryness may be significant and ability to wear contact lenses may be impaired for a period of days to weeks in most cases.