Isotretinoin

Isotretinoin is a unique therapy because it targets all aspects of the acne disease process. Its effects are summarised in Box 10.4.

Box 10.4 Effects of isotretinoin Decreases the size of, and secretions from, the sebaceous glands; Normalises the follicular keratinisation thus preventing follicular plugging and comedone formation; Alters the microenvironment of the follicle so that it is not conducive to P. acnes growth; Has an anti-inflammatory effect.

Taking isotretinoin can reduce the sebum production by up to 90%; the effect of this is that P. acnes levels decrease significantly (Gollnick et al., 2003). This in turn leads to a significant decrease in inflammatory lesions. Most cases respond to a single 4–6 month course. Pustules clear more rapidly than papules and nodules and those lesions on the face, upper arms and legs clear more quickly than those on the trunk. Beneficial effect may take 1–2 months to notice and occasionally the acne may worsen in this period of time prior to improving. Patients need to be warned of this fact.

Dosing ranges from 0.1–2.0 mg/kg but in reality doses higher than 1.0 mg/kg are rarely used. In order to minimise potential side effects (especially a flare-up of the acne), a starting dose of 0.5 mg/kg/day for the first month may be advisable. If tolerability is not a problem, this dose may be followed by 1 mg/kg per day for the rest of the course. More severe deeper nodular acne may need a longer treatment period.