Purpose

• Doxycycline and other antibiotics are generally prescribed as initial treatment for severe acne when topical treatments do not work. Usually antibiotics are prescribed for short-term therapy, but some people take them for acne treatment for many months or even years. An alternative strategy is to use doxycycline at high dosages for a short time instead of taking low dosages for long time frames, in order to prevent bacteria from becoming drug-resistant.
  
  

Dosage

• Doxycycline is the most frequently prescribed oral antibiotic in the U.S. for acne treatment, according to a study published in a 2007 issue of SkinMed. The usual dose is 50 to 100 milligrams taken twice daily. One brand, Doryx, is a time-released form that is taken once a day. Doryx is more expensive, but decreases stomach upset that often occurs when taking doxycycline.
  
  

Additional Uses

• Doxycycline also is prescribed for bacterial infections such as chlamydia, gonorrhea, syphilis, urinary tract infections, Lyme disease and anthrax. It is also effective in reducing rosacea, a skin disorder that causes redness, inflammation, swelling and sometimes small pimples.
  
  

Side Effects

• People taking doxycycline should avoid overexposure to sunlight, because doxycycline causes sensitivity to light, which can result in sunburn. Other side effects, which usually disappear after a short time, can include diarrhea, fatigue, lack of appetite, nausea and stomach pain. Taking doxycycline with food can eliminate problems with nausea. Serious symptoms that may require discontinuing doxycycline use include rash or itching, severe diarrhea, abnormal bruising or bleeding, and infrequent urination.
  
  

Combination Treatment

• Doxycycline is usually intended as a treatment in combination with a topical retinoid medication, a type of vitamin A that reduces acne. Doxycycline typically is prescribed after topical treatment has not worked, but continuing to use the topical treatment along with the antibiotic is "significantly superior" to doxycycline alone, as shown by the SkinMed study.