Drugs like quinine, mepacrine and chloroquine, apart from their activity as anti-malarials, have been found to be excellent sunscreens when given systemically. Out of these, quinine was found to be toxic when used for prolonged periods, while mepacrine produces a yellowish discoloration of the skin.
Chloroquine therefore, has been the mainstay of therapy as an oral sunscreen. It has been found to be particularly useful in discoid lupus erythematosus and polymorphous light sensitive eruptions. When given for prolonged periods, chloroquine has also been observed to produce the following side effects:
Ophthalmic toxicity: Patients may develop an early but transient disturbance in the vision due to corneal oedema or a late defect in the vision due to the deposition of precipitates on the posterior surface of the cornea. In the late stages, development of retinopathies may lead to a permanent damage to the vision.
Cutaneous toxicity: Chloroquine has been associated with the appearance of lichenoid drug eruptions, exfoliative dermatitis and depigmentation of the hairs. These side effects are, however, quite rare.
Fairly good results of chloroquine therapy without any major side effects have been observed by giving only one or two tablets of chloroquine a day for 15 days in a month and repeating such courses three or four times at the maximum.