Tretinoin, topical Retin

Thalidomide (Thalomid) Topotecan (Hycamtin) Tretinoin, Topical [Retinoic Acid] (Retin-A, Avita, Renova, Retin-A Micro)... 

In vitro and in vivo pharmacokinetic studies with tretinoin cream and gel indicated that less than 0.3% of the topically applied dose is bioavailable. Circulating plasma levels of tretinoin are only slightly elevated above those found in healthy normal controls. Estimates of in vivo bioavailability ot Retin-A M/cro following single and multiple daily applications, for a period of 28 days with the 0.1 % gel, were... 

Dermatological reactions to lithium include acne, follicular eruptions, and psoriasis. Hair loss and thinning also have been reported. Except for cases of exacerbation of psoriasis, these reactions are usually benign and may not warrant discontinuation of lithium treatment. Lithium-induced acne responds to topical treatment with retinoid acid, such as tretinoin (Retin-A). 

Topical retinoic acid is applied initially in a concentration sufficient to induce slight erythema with mild peeling. The concentration or frequency of application may be decreased if too much irritation occurs. Topical retinoic acid should be applied to dry skin only, and care should be taken to avoid contact with the corners of the nose, eyes, mouth, and mucous membranes. During the first 4-6 weeks of therapy, comedones not previously evident may appear and give the impression that the acne has been aggravated by the retinoic acid. However, with continued therapy, the lesions will clear, and in 8-12 weeks optimal clinical improvement should occur. A timed-release formulation of tretinoin containing microspheres (Retin-A Micro) delivers the medication over time and may be less irritating for sensitive patients. 

There are many types of preparations that contain retinol. Absorption is greatest for aqueous preparations, intermediate for emulsions, and slowest for oil solutions. Whereas oil-soluble preparations may lead to greater hepatic storage of the vitamin, water-miscible preparations usually provide higher concentrations in plasma. Vitamin A is available as capsules. Tretinoin (all-trans-retinoic acid Retin A) is available for topical use. Isotretinoin (13-ri.s-retinoic acid Accutane) is available for oral use, as is etretinate (Tegison). 

Epidermal keratinization and mucous membrane squamous metaplasia respond to both oral and topical vitamin A therapy. Vitamin A exists in three forms retinol, retinal, and retinoic acid.VitaminA increases the mucous production of goblet cells and perhaps the aqueous and lipid components of the tears as well. Tretinoin is a normal metabolite and the carboxylic form of retinol. Retinol is present in tears and the lacrimal gland appears to be its major provider. Retinoic acid has been shown to be effective in ocular surfece disorders such as squamous metaplasia by reversing the corneal and conjunctival keratinization and improving epithelium wound healing rate. 

Tretinoin (Retin-A) is applied topically (not in combination with other keratolytics). It may promote UV-induced skin cancer. Tretinoin should be avoided in sunny weather, and in pregnancy. Benefit is seen in about 10 weeks. Adapalene, a synthetic retinoid, may be better tolerated. 

A baby was born missing its right ear and external auditory canal. At 20 months an MRI scan of the brain showed focal atrophy and encephalomalacia of the right parieto-occipital lobe. His mother had used topical tretinoin (Retin A 0.025%) on her face and a large surface of the back before conception and during the first 2-3 months of pregnancy. His father had used oral isotretinoin before conception. 

Treatment has been difficult as the modalities that are useful in acne vulgaris are often ineffective in chloracne. Topical application of retinoic acid (0.005-0.3% concentration) or of tretinoin (Retin-A) gel or cream is of some benefit in controlling comedones, but other topical agents are of little use (Caputo et al. 1988). A combination of tetracycline and short courses of orally administered prednisone helped with severe inflammatory cases. A trial regimen of methotrexate, 25 mg every 10 days for several months was unsuccessful (Taylor et al. 1977). 

Retinoids have multiple properties in embriogenesis, growth control and differentiation of adult tissues, reproduction, and sight. In dermatology their use is well established for psoriasis, hereditary disorders of keratinization, acne, and skin aging. The most commonly used retinoids are aH-trans retinoic acid (tretinoin used topically), 13-cis retinoic acid [isotretinoin used both orally and topically), retinaldehyde/retinal and retinol [both of which are used topically). In addition there are the synthetic retinoids etretinate, acitretin, adapalene, tazarotene, etc. 

Tretinoin formulations available today include the traditional topical tretinoin cream (0.025%, 0.05%, 0.1%), gel (0.025%, 0.01%) or liquid (0.025%) developed for acne therapy (Retin-A ),... 

---