Acne is caused by the effects of hormones on the pilosebaceous unit, consisting of a hair follicle, sebaceous gland, and a hair. The follicle becomes obstructed and an overgrowth of a normal skin bacteria, Propionibacterium acnes, causes destruction of the lining of the follicle. This process allows follicular material to enter the dermis, causing an inflammatory response. For a more detailed description of this process, see What Causes Acne?
How Antibiotics Work for Acne
Antibiotics work by several mechanisms. The most important is the decrease in the number of bacteria in and around the follicle. Antibiotics also work by reducing the irritating chemicals produced by white blood cells. Finally, antibiotics reduce the concentration of free fatty acids in the sebum, also reducing the inflammatory response. The most frequently used antibiotics for acne are summarized here.
Tetracycline is the most widely prescribed antibiotic for acne. The usual starting dose is 500 mg twice a day continued until a significant decrease in acne lesions is seen. The dose can then be decreased to 250 mg twice a day or discontinued. The main drawback for this antibiotic is that it must be taken on an empty stomach to be the most effective. For a teenage boy who eats frequently, this can be very difficult. Tetracycline should not be given to pregnant women or children under 9 years of age.
Erythromycin is a very commonly used antibiotic for acne. It has several advantages over tetracycline. First, it has anti-inflammatory properties that help reduce redness in lesions, in addition to killing bacteria. Also, it can and should be taken with food - a benefit for teenagers. The dosage of erythromycin varies with the type used, but it is typically prescribed as 250 - 500 mg twice a day. It can cause stomach upset and nausea, but can be used in pregnant women.
Minocycline is a tetracycline derivative that has been used effectively for decades as a treatment for acne. It is especially useful for pustular type acne. While the absorption of minocycline is decreased with food, it is not as significant as the decrease seen with tetracycline. The usual starting dose is 50 to 100 mg twice a day. Major side effects of minocycline include dizziness, nausea, vomiting, skin pigmentation changes, and tooth discoloration. The skin and tooth changes are seen more often in people who have taken minocycline for a long time.
Doxycycline is often used for people who do not respond to or cannot tolerate erythromycin or tetracycline. The dosage of doxycycline is started at 50 to 100 mg twice a day. It should be taken with food; otherwise it can cause significant nausea. Doxycycline is more likely than tetracycline to increase sensitivity to the sun, or cause sunburns.
Clindamycin is very useful as an oral antibiotic for acne, but it is most widely prescribed as a topical antibiotic. The starting dose is 75 to 150 mg twice a day. The major side effect of clindamycin therapy is serious intestinal infection called pseudomembranous colitis caused by the bacteria, Clostridium difficile.
Side Effects of All Antibiotics
All antibiotics can cause candida vaginal yeast infections in women. Tetracycline seems to be the antibiotic that most frequently has this side effect. All oral antibiotics can also lessen the effectiveness of birth control pills,