| Local irritation The presence of cutaneous irritative signs (eg erythema, peeling, pruritus, sunburn, etc) should prohibit initiation or recommencement of treatment with Retin-A until the symptoms resolve.In certain sensitive individuals, topical use may induce severe local erythema, swelling, pruritus, warmth, burning or stinging, blistering, crusting and/or peeling at the site of application. If the degree of local irritation warrants, the patient should be directed to apply the medication less frequently or discontinue its use temporarily. If a patient experiences severe or persistent irritation, the patient should be advised to discontinue application of Retin-A completely and, if necessary, consult a physician.Weather extremes, such as wind or cold, also may be irritating to patients being treated with Retin-A.Exposure to sunlight, including ultraviolet sunlamps, should be avoided or minimised during the use of tretinoin. Patients with sunburn should be advised not to use the product until fully recovered because of potential severe irritation to skin. A patient who experiences considerable sun exposure due to occupational duties and/or anyone inherently sensitive to the sun should exercise particular caution. When exposure to sunlight cannot be avoided, use of sunscreen products and protective clothing over treated areas is recommended.General precautions for use: Before application of Retin-A, areas to be treated should be cleansed thoroughly.Abstain from washing the treated area frequently: twice daily is sufficient. Use of mild soap is recommended. Dry skin without rubbing.Avoid contact with eyes, eyelids, nostrils, mouth and mucous membranes. If contact in these areas occurs, careful washing with water is recommended.Warning: The weight of evidence indicates that topical tretinoin is not carcinogenic. In a lifetime study of CD-1 mice, a low incidence of skin tumours was seen at 100 and 200 times the estimated clinical dose but, although no such tumours were seen in the study controls, the incidence in these treated animals was within the historic control range for CD-1 mice.Studies in hairless albino mice suggest that tretinoin may accelerate the tumorigenic potential of UVB light from a solar simulator. In other studies, when lightly pigmented hairless mice treated with tretinoin were exposed to carcinogenic doses of UVB light, the photocarcinogenic effects of tretinoin were not observed. Due to significantly different experimental conditions, no strict comparison of this disparate data is possible. Although the significance of these studies in man is not clear, patients should avoid or minimise exposure to sunlight.The weight of evidence indicates that topical tretinoin is not mutagenic. The mutagenic potential of tretinoin was evaluated in the Ames assay and the in vivo mouse micronucleus assay, both of which showed negative findings.
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