Abnormalities in plasma lipids are a recognized side effect of isotretinoin therapy for nodulocystic acne. We studied 60 patients during 20 weeks of isotretinoin therapy, to measure changes in plasma lipids and lipoproteins, to compare plasma lipid responses in men and women, and to determine whether there are alterations in levels of lipoprotein lipase or hepatic triglyceride lipase that could explain the development of isotretinoin-induced hypertriglyceridemia. Mean triglyceride levels rose in men and women, with maximum mean increases of 46.3 mg per deciliter (P less than 0.0001) and 52.3 mg per deciliter (P less than 0.002), respectively. The maximum level was reached by 4 weeks of therapy in men but not until the 12th week in women. Nine of 53 patients (17 per cent) completing 20 weeks of isotretinoin therapy acquired hypertriglyceridemia, with values of 200 to 600 mg per deciliter. Both men and women had significant increases in mean plasma levels of cholesterol and low-density-lipoprotein cholesterol and decreases in mean levels of high-density-lipoprotein cholesterol. There were no significant changes in mean levels of lipoprotein lipase or hepatic triglyceride lipase. Plasma lipid and lipoprotein levels returned to base line by eight weeks after discontinuation of the drug. If sustained over a long period, the change in the ratio of low-density-lipoprotein cholesterol to high-density-lipoprotein cholesterol that we observed, from 2.4 to 3.0 (P less than 0.0001), would predict an increased risk of cardiovascular disease.

This review examines the commonly available topical acne agents and factors that determine their percutaneous absorption. Reported and theoretical adverse effects from systemic exposure are detailed. The topical retinoid class, which includes tretinoin, adapalene and tazarotene, and the topical antibacterials, clindamycin and erythromycin, are regulated by prescription in most countries. Used appropriately, the above-mentioned drugs deliver, at most, miniscule amounts of active ingredient into the circulation. Clear-cut links to systemic toxicity in humans are practically nonexistent, except in the case of topical clindamycin, which has been associated with diarrhea rarely, and there have been 2 cases of pseudomembranous colitis reported. Birth defects have occurred in two patients treated with tretinoin and one patient treated with adapalene, but causation was not proven. Another prescription drug, 20% azelaic acid, is associated with relatively high systemic exposure, which is presumed innocuous because it is a normal dietary constituent whose endogenous levels are not altered by topical use. Benzoyl peroxide, salicylic acid, sulfur, and sodium sulfacetamide are available in concentrations of 2% or more in over-the-counter acne treatments and some prescription products. All of these agents are known to exhibit some degree of percutaneous absorption. They remain largely unregulated because, other than skin irritation, only local allergic contact dermatitis from benzoyl peroxide in about 2.5% of patients and rare local and systemic hypersensitivity reactions from sodium sulfacetamide have been reported. Salicylism has occurred using methyl salicylate ointments and high concentrations of salicylic acid on widespread areas of hyperkeratotic skin, but there are no known cases resulting from salicylic acid acne products. Caution is advised in special circumstances, such as during childhood, pregnancy, lactation and concomitant therapy with other drugs, because relevant studies are lacking. Animal data support avoidance of many topical agents, particularly known teratogens such as retinoids and salicylic acid, in pregnant women. Salicylate avoidance is advised during lactation, because aspirin use carries the risk of bleeding disorders in nursing infants.

This issue provides a clinical overview of atopic dermatitis (exzema) focusing on prevention, diagnosis, treatment, practice improvement, and patient information. Readers can complete the accompanying CME quiz for 1.5 credits. Only ACP members and individual subscribers can access the electronic features of In the Clinic. Non-subscribers who wish to access this issue of In the Clinic can elect "Pay for View." Subscribers can receive 1.5 category 1 CME credits by completing the CME quiz that accompanies this issue of In the Clinic. The content of In the Clinic is drawn from the clinical information and education resources of the American College of Physicians (ACP), including PIER (Physicians' Information and Education Resource) and MKSAP (Medical Knowledge and Self Assessment Program). Annals of Internal Medicine editors develop In the Clinic from these primary sources in collaboration with the ACP's Medical Education and Publishing division and with assistance of science writers and physician writers. Editorial consultants from PIER and MKSAP provide expert review of the content. Readers who are interested in these primary resources for more detail can consult www.acponline.org, http://pier.acponline.org, and other resources referenced within each issue of In the Clinic.

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Topical retinoic acid was introduced for acne treatment three decades ago. Since that time, researchers have discovered thousands of retinoids, originally defined as chemical analogs of vitamin A. After the identification of nuclear retinoid receptors in 1987, the definition of this class expanded to include molecules that bind to and activate such receptors. The receptor-selective retinoid agents, adapalene and tazarotene, were developed in the 1990s. Other innovations of the past decade include retinoid formulations and methods aimed at limiting retinoid absorption. Cutaneous irritation may be reduced without losing retinoid efficacy by inhibiting retinoid penetration into the deep epidermis and dermis. Examples include tretinoin in slow-release vehicles and the short-contact method of tazarotene gel therapy. Only trace amounts of adapalene are absorbed after topical application, perhaps explaining its relatively low irritancy. New formulations of existing agents, such as additional concentrations of tretinoin in microsphere gel and cream formulations of tazarotene, are now under investigation for acne. Current research focused on receptor selectivity holds the promise of yielding new retinoid molecules with improved benefits and safety.