Retinoid

Retinoids are vitamin A derivatives. The most commonly used of these are tretinoin and isotretinoin. They can be administered locally or orally.

How do the retinoids work?

The retinoids act by returning the follicular keratinisation cycle to normal and by inhibiting the function of sebaceous glands. They also reduce the size of these glands. Result: the corneal plug (comedon) is reduced. Comedons and cysts therefore gradually disappear. These medicines also increase the permeability of the follicular wall to inflammatory agents. This action helps to reduce inflammatory lesions

Do they have any contraindications or precautions?

Retinoids increase sensitivity to sunlight. So it is essential for patients to protect themselves from sunlight during treatment. Other side-effects can also occur. These include dry mucosal membranes and joint pains. Isotretinoin can also have serious teratogenic effects on the unborn child. Any woman who becomes pregnant during treatment exposes the foetus to high risks of malformations: absence or incorrect implantation of an ear, abnormally large head, excessively small chin and cardiac, thymus or nervous system malformations. All female patients of child-bearing age must be followed up closely. They must also be using a contraceptive and perform regular pregnancy tests throughout treatment. Since 15 March 2010 the prescribing doctor in France must give a "patient diary" to any woman of child-bearing age who wishes to take this type of treatment. Administration of isotretinoin has also been associated with episodes of depression and even cases of suicide.

Source: Merck Manuel, 4^th edition