Retigel: Apply Isotretinoin 0.05% gel cautiously over the affected area once or twice daily. Patients should be advised that 6-8 weeks of treatment may be required before a therapeutic effect is observed. The safety and efficacy of Isotretinoin have not been established in children since acne vulgaris rarely present in this age group. There are no specific recommendations for use in the elderly. Acne vulgaris does not present in the elderly.