Descriptions of each prescription acne treatment available in Canada and their mechanisms of action.
PRESCRIPTION MEDICATIONS
TOPICAL MEDICATIONS
The most effective acne medications are available only by physician prescription. As with any potent pharmaceutical agent, they should be used only after examination by a physician and under the supervision of a physician and pharmacist. Prescribed topical medications include the topical antibiotics and topical retinoids.
TOPICAL ANTIBIOTICS
The antibiotics used topically in treatment of acne are believed to be effective for reasons in addition to anti-bacterial activity. All antibiotics are powerful drugs that must be used as directed by a physician. Topical antibiotics alone are not generally recommended. In fact, long-term use may increase risk for antibiotic resistance in skin bacteria. They should be used in combination with other topical agents.
Azelaic acid—a naturally occurring acid that has been adapted to use for treating acne. Its anti-acne activities are antimicrobial (reducing populations of Propionibacterium acnes ), and decrease of hyper-keratinization (may inhibit comedo formation). P. acnes is the predominant microbiologic organism in sebaceous follicles. It is generally accepted that P. acnes plays a role in acne by releasing metabolic products that contribute to the inflammation of acne. Azelaic acid is applied as a cream. A course of treatment may require several months.
Erythromycin—a member of the macrolide family of antibiotics, erythromycin is active against a broad spectrum of bacteria. Systemically it is used to treat diseases such as pneumonia. Its principal topical use is in treatment of acne vulgaris, for its anti-acne effects are both antimicrobial and anti-inflammatory. A combination erythromycin/benzoyl peroxide agent combines the effects of two antimicrobial agents plus reduction of skin oiliness.
Clindamycin—a semisynthetic antibiotic with antimicrobial activity similar to that of erythromycin. Clindamycin has a long history of use in treatment of acne.
Tetracycline—This group of broad-spectrum antibiotics were among the first antibiotics adapted to the topical treatment of acne, but today are used much less frequently in Canada and the developed world as topical medication. Undesirable side effects of odor and yellow staining of skin limited the acceptance of tetracycline topical agents.
Sulfonamide—The sulfonamides are among the oldest antibacterial agents, in use since the 1930s. Sodium sulfonamide lotion is available for treatment of acne and reducing inflammatory lesions.
Many other antibiotics are used topically to treat skin infections. The antibiotics discussed above are those in current topical use in Canada to treat acne vulgaris. A dermatologist can determine for each individual patient (1) whether topical antibiotics are appropriate, and (2) which topical antibiotic should be prescribed.
TOPICAL RETINOIDS
Retinoids are a class of molecules in the vitamin A family of molecules. The retinoids are very potent as anti-acne medications. The retinoid activation of specific RARs normalizes abnormal growth and death of cells in the sebaceous follicle; abnormal follicular cell cycles are believed to play a major role in plugging sebaceous follicles and causing comedones to form.
Retinoids are adapted as anti-acne medications in both topical and systemic forms; the systemic form will be discussed next month in the last of this three-part series on acne treatments.
The most common side effects of topical retinoids are redness, dryness, peeling and itching of skin in the areas of retinoid application. Risk for birth defects is a major side effect of systemic retinoids; the risk is much lower for topical retinoids but should be discussed with the physician when a female acne patient is pregnant or likely to become pregnant.
The topical natural and synthetic retinoids currently available as acne medications in the United States are:
Tretinoin—also known as vitamin A acid, a natural retinoid. Tretinoin is a molecule in the very large family of vitamin A-type molecules that are important for good vision, good skin quality and general good health. Tretinoin influences skin cell growth and death cycles by a cascade of events that begins with binding to RARs and ends with both direct and indirect alteration of genes that control follicular cell cycles. Topical tretinoin is available as a cream, gel or solution—a dermatologist will prescribe the form of application best for each individual patient. The maximum benefit of tretinoin’s anti-acne activity may require several weeks of treatment.
Adapalene—a synthetic retinoid applied as a gel or cream, it has potent retinoid and anti-inflammatory activity. Side effects are similar to those of tretinoin.
Tazarotene—a synthetic retinoid applied as a gel or cream, it acts on the follicular cell cycle by a biochemical pathway different from that of tretinoin. Side effects are similar to those of tretinoin.
ORAL ANTIBIOTICS
Broad-spectrum antibiotics have been a mainstay of systemic therapy for moderate to severe and persistent acne for many years. Numerous studies have provided evidence supporting the effectiveness of oral broad-spectrum antibiotics. The anti-acne activity of oral antibiotics appears to include physiologic effects in the sebaceous follicle as well as reduction of bacterial populations in the follicle.
Oral tetracycline has a long history in the treatment of acne, and remains one of the most widely used. A typical tetracycline regimen for treating moderate to severe acne is a starting dose of 500 to 1000 milligrams a day, decreased as improvement is noted. Long-term, low-dose tetracycline therapy may be continued for many months to maintain suppression of acne. Higher doses may be prescribed for very severe acne, with regular monitoring for systemic side effects. Tetracycline may cause staining of teeth in children, and should generally not be taken by children younger than 8 years of age. Oral tetracycline may cause permanent teeth staining or skeletal defects in a fetus and therefore should not be taken by a woman who is pregnant.
Oral erythromycin is an alternative to tetracycline that is safe for use in pregnant women and young children.
Oral minocycline and doxycycline are synthetically derived from tetracycline. Some evidence suggests that these antibiotics may be more effective than tetracycline in treating acne. Minocycline has a long history of use in the treatment of acne. Doxycycline may induce sensitivity to sunlight. Neither should be taken by pregnant women.
HORMONAL THERAPIES,
Androgenic ("male") hormones are known to have physiologic effects on sebaceous follicles that promote the development of acne. The purpose of hormonal therapy is to block or lessen acne-promoting effects of androgenic hormones.
Estrogen is a "feminine" hormone that counteracts effects of androgenic hormones and decreases sebum secretion in the sebaceous follicles. Estrogen has wide-ranging physiologic effects in the body and its use must be closely monitored—often by both a gynecologist and a dermatologist. The use of estrogen alone in the treatment of acne may be indicated in carefully selected patients.
Estrogen-containing oral contraceptives are prescribed more frequently than estrogen alone in hormonal therapy of acne in females. The effects of estrogen are balanced by other hormonal constituents of oral contraceptives. While oral contraceptives have a better safety profile than estrogen alone in treating acne, their use must be monitored for side effects of nausea, weight gain, menstrual spotting and breast tenderness. Hormonal therapy may be a treatment of choice for women whose acne does not respond to other medication.
CORTICOSTEROIDS
These powerful anti-inflammation drugs may be prescribed for short courses to treat very severe acne. Their metabolic effects limit long-term use. Low-dose corticosteroids are helpful in specific instances—for example, to suppress excessive secretion of androgenic hormones. Corticosteroids can induce development of steroid acne with prolonged use.
OTHER HORMONE THERAPIES
The anti-androgen spironolactone reduces sebum production and improves acne in some patients. Side effects include irregular menstruation in women, breast tenderness, headache and fatigue. The anti-androgen may be used along with an oral contraceptive to reduce irregular menstrual bleeding.
Flutamide is an anti-androgen sometimes prescribed together with an oral contraceptive to treat acne and hirsutism (excessive growth of facial and body hair) in women. It should not be taken by pregnant women.
ISOTRETINOIN
Isotretinoin is the most effective drug available for treatment of severe cystic acne and acne resistant to other medications. It is a synthetic retinoid. The retinoids are molecules of the vitamin A family of molecules. Isotretinoin is a potent drug, usually reserved for treatment of very severe cystic acne and acne that is resistant to other medications. It is very effective in treating all forms of acne; the remissions achieved with isotretinoin usually last for many months to many years.
A number of side effects are associated with isotretinoin therapy, the most serious being the potential to cause severe birth defects to a developing fetus. The most common side effect of isotretinoin therapy is dryness of the skin and mucous membranes. Other, less common, side effects include nausea and vomiting, bone and joint pain, headache, thinning hair, psychological depression, and changes in blood and enzyme profiles monitored in regular follow-up examinations. Regularly scheduled monitoring for side effects is recommended by the physician. For most persons treated with isotretinoin, side effects are tolerable and not a reason to discontinue therapy before remission is achieved. It is imperative that women of childbearing potential follow the pregnancy prevention program and guidelines. Women who are planning a pregnancy, are pregnant or are nursing must not use isotretinoin. It is recommended that women planning a pregnancy discontinue the use of isotretinoin for one month.
