Isotretinoin (13-cis retinoic acid) is an oral retinoid that has been available for the treatment of acne since 1971 in Europe, and since 1983 in the United States. The Food and Drug Administration (FDA) indication for the use of isotretinoin is severe, nodulocystic acne that has not been helped by other treatments, including antibiotics. However, patients with other forms of acne have also benefited from isotretinoin. These patients include those with: significant acne unresponsive to treatment including oral antibiotics, acne that results in significant physicial or emotional scarring, and patients with gram-negative folliculitis, pyoderma faciale, and acne fulminans (88,89).
The exact mechanism of action of isotretinoin is not known. It is believed that 13-cis – retinoic acid exerts its action by isomerization to all-trans-retinoic acid, which then interacts with the retinoid receptors (90). It is the only acne medicine available that affects all four pathogenic factors of acne. Isotretinoin is comedolytic, reduces sebaceous gland size (up to 90%), and suppresses sebum production which in turn inhibits P. acnes and its ability to elicit inflammation (91). During the course of isotretinoin therapy, the pustular lesions generally clear first, and the codemos will be the last to resolve. Lesions on the face and upper arms tend to respond faster to isotretinoin than lesions on the trunk (92).