RETIN-A

Fi re 12.6 Schematic diagram Illustrating the proton movements in the photocycle of bacteriorhodopsin. The protein adopts two main conformational states, tense (T) and relaxed (R). The T state binds trans-tetinal tightly and the R state binds c/s-retinal. (a) Stmcture of bacteriorhodopsin in the T state with hflus-retinal bound to Lys 216 via a Schiff base, (b) A proton is transferred from the Schiff base to Asp 85 following isomerization of retinal and a conformational change of the protein. 

Retacnyl (Galderma) Retin A (Janssen-Cilag) Retinova (Roc)... 

It is still debatable whether preparation of the skin is required for deep chemical peeling. We feel that topical retin A preparations used daily for 3-6 weeks prior to the procedure may create better and more even penetration of the peeling solution in sebaceous and hyperkeratotic skins. We did not find any benefit of this regimen in thin-skinned patients. 

Tretinoin Retin-A Retin-A Micro 0.025%, 0.05%, and 0.1 % cream 0.01%, 0.025% gel 0.05% solution 0.04% and 0.1% gel Apply a small amount once daily before bedtime Skin irritation, dryness, photosensitivity initially may worsen acne Skin irritation, dryness, photosensitivity initially may worsen acne... 

The visual pigment present in rods has been termed rhodopsin and consists of 11-m-retinal, a derivative of vitamin A1( and a lipoprotein called opsin. Recent evidence(43) suggests that in native rhodopsin the retinal chromo-phore is covalently bonded to a phosphatidylethanolamine residue of the lipid portion of opsin. The structure of 1 l-cis-retinal is as follows ... 

Horwitz, J., Heller, J. Photoselection and linear dichroism of retinals. A method for identification and measurement of various geometrical isomers. J. Biol. Chem. 248, 1051-1055 (1973). 

Special tasks. Some lipids have adopted special roles in the body. Steroids, eicosanoids, and some metabolites of phospholipids have signaling functions. They serve as hormones, mediators, and second messengers (see p.370). Other lipids form anchors to attach proteins to membranes (see p.214). The lipids also produce cofactors for enzymatic reactions—e.g., vitamin K (see p.52) and ubiquinone (see p.l04). The carotenoid retinal, a light-sensitive lipid, is of central importance in the process of vision (see p.358). 

Tretinoin (Various), Avita (Bertek), Retin-A (Ortho)... 

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... 

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

Foscarnet is indicated for the treatment of CMV retinitis in AIDS patients. Its effectiveness is comparable to that of ganciclovir these drugs are synergistic when given to counteract refractory retinitis. A decreased incidence of Kaposi s sarcoma has been observed in AIDS patients who have undergone foscarnet therapy. 

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. 

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