Acne is a skin condition in which pimples (comedones) appear on the skin, usually on the face, chest, or back. Adolescents and young adults are most often afflicted. Acne tends to be more severe in males; however, with females, acne may persist into adulthood.
Causes and Types of Acne
The skin has hair follicles that each contains a hair shaft and an oil gland. The oil glands continuously produce and secrete oil to lubricate and protect the skin. However, when dead skin cells and oil (sebum) build up inside the follicle and close off the follicle's pore, pimples appear, in the form of either blackheads or whiteheads. If the plugging material protrudes from the opening at the surface of the skin, this plug of oil and dead cells darkens, forming blackheads; if the plugging material does not protrude, whiteheads form. This type of acne is referred to as comedonal. When the accumulated material of a closed-off pimple causes the follicular wall to rupture, an internal inflammatory reaction occurs, causing oil, dead cells, and bacteria to spill onto the skin. The skin around the pore becomes red and inflamed, and the result is inflammatory acne. When white blood cells infiltrate the area to repair the inflammation, papules, nodules, and cysts may develop. Papules form near the surface of the skin, whereas nodules and cysts are caused by inflammation deeper in the skin.
In the past many persons attributed abnormally high oil secretion and the development of acne to the afflicted individual's diet and hygiene. However, current research suggests that oil secretion is under genetic control, primarily related to the ability of androgenic hormones to stimulate oil secretion. The bacterial species Propionibacterium acnes is believed to play a role in converting acne into an inflammatory condition. Stress and the use of certain cosmetics may also be contributing factors.
Treatment of Acne
There are many ways to treat acne. Gentle washing of the face is important because it helps to remove accumulated oil, bacteria, and dead cells on the skin's surface. Other treatments help to unclog pores, kill bacteria, or minimize oil. Products that help to open up pores include mild cleansers, scrubs, exfoliants, and masques. All of these are available without a prescription. Exfoliants remove the outer layer of skin, thus opening pores. These agents, as well as astringents and toners, help to wipe away excess oil. Antibacterial agents are used to kill bacteria. The most common mild antibacterial agent is benzoyl peroxide. It is available in the form of creams or lotions that are applied to affected areas, and may even be found in some cleansers. Other antibacterial agents available by prescription include topical antibiotics such as erythromycin , clindamycin, and sulfacetamide, and oral antibiotics such as tetracycline, doxycycline, minocycline, and sulfa drugs.
Benzoyl peroxide. Benzoyl peroxide encourages peeling of the outermost layer of the skin and, as mentioned previously, is a mild bactericidal agent. It kills bacteria by virtue of its oxidizing properties. It is often included in prescription acne medications, and in nonprescription acne products such as gels, lotions, and cleansers. It may be used alone or with other treatments. At even low concentrations (2.5–10%), benzoyl peroxide diminishes the population of Propionibacterium acnes. The most common adverse effects are dry skin and bleaching of the skin.
Retinoids. The term "retinoid" refers to retinol or other closely related derivatives, either natural or synthetic. Retinoids may or may not have retinol-like ( vitamin A–like) activity. Retinoids affect epithelial cells by binding to receptors inside these cells, inducing alterations in the transcription of genes. Retinoids enhance the synthesis of some proteins, such as proteins that serve as receptors for certain hormones and growth factors, and reduce the synthesis of others. Some of the most commonly prescribed treatments for acne—tretinoin, isotretinoin, and adapalene—are retinoids. (See Table 1.)
Tretinoin became available as a topical treatment for acne in the United States in 1971. Tretinoin is also known by its chemical name, all- trans -retinoic acid. It increases the turnover of skin cells at the surface of the hair follicle. This leads to the extrusion of comedones. Side effects include local skin irritation and increased sun sensitivity. Newer preparations of tretinoin, designed to achieve slow absorption of the drug into epithelial cells, cause less skin irritation than forms available initially. Improvement in acne may not be noticeable until two to three weeks after treatment begins.
In 1982 the Food and Drug Administration (FDA) approved the oral use of isotretinoin (Accutane) for the treatment of severe nodulocystic acne that has not responded to antibiotics. This drug is not active topically. As the name suggests, isotretinoin is an isomer of tretinoin. The only structural difference between the two molecules lies in the spatial arrangement of the atoms around one carbon-carbon double bond. Isotretinoin has the chemical name 13- cis -retinoic acid. Through mechanisms not well understood, it decreases the size of the sebaceous glands and inhibits closure of the pore. These actions may diminish the ultimate formation of cysts. As is
|GENERIC AND BRAND NAMES OF SOME COMMONLY PRESCRIBED ACNE MEDICATIONS|
|Brand Name||Generic Name|
|SOURCE: Data obtained from http://www.healthsquare.com/drugmain.htm|
|Desquam-E, Benzac W, Benzagel, Clinac BPO, Triaz||benzoyl peroxide|
|Retin-A, Renova, Avita||tretinoin|
the case with other retinoids, arachidonic acid release from macrophages is inhibited. This may account for the anti-inflammatory effects of retinoids. Isotretinoin's anti-acne effects can last for months to years following a twenty week course. And, unlike antibiotic treatments, treatment with isotretinoin does not promote antibiotic-resistant bacteria.
Reservations toward the use of isotretinoin (Accutane) are related to its severe side effects. Any of the retinoids, including vitamin A, can have severe side effects. Some of the symptoms of hypervitaminosis A are the same as the major toxic effects associated with the therapeutic use of retinoids. When retinoids are applied to the skin, few systemic side effects occur. For isotretinoin, which is administered orally, side effects are much more common. Among those reported are skin blistering, skin fragility, hair loss, headache, nausea, vomiting, visual disturbances, and increased levels of triglycerides and decreased levels of high density lipoproteins in blood plasma. Furthermore, because isotretinoin can cause severe birth defects, including physical abnormalities and mental retardation, a female patient taking it must not become pregnant. Female patients must obtain a negative serum pregnancy test before treatment can begin, and written consent forms must be signed. These patients should also not become pregnant for some time after the drug has been discontinued. In 1998, as a result of medical reports associating Accutane use with depression and suicide, the FDA issued new safety information regarding isotretinoin.
Newer retinoids. Medical chemists are often able to modify the structure of a drug that has unwanted side effects or problems making it difficult to administer. Even slight structural changes may result in an improved pharmacological agent that requires lower dosing, or has fewer side effects, or both. The development of adapalene is an example. A better retinoid might have enhanced stability, enhanced anti-inflammatory effects, or result in decreased skin irritation. The naphthoic-acid derivative adapalene, developed in the 1990s, works better and with less local skin irritation than earlier retinoids. The reduced side effects are attributed to the selectivity of adapalene for nuclear retinoic acid receptors within follicular epithelial cells. Although many persons will have acne during their teen years, effective treatment is available.
SEE ALSO Retinol .
Jennifer L. Powers
Bershad, Susan V. (2001). "The Modern Age of Acne Therapy: A Review of Current Treatment Options." The Mount Sinai Journal of Medicine 68(4–5):279–286. Full text also available from http://www.mssm.edu/msjournal .
Information available from http://www.accutaneaction.com .
Information available from http://www.differin.com .
Information available from http://www.fda.gov .
Information available from http://healthsquare.com/drugmain.htm .