Nearly every case of acne can be treated, regardless of its severity, according to the American Academy of Dermatology, or AAD. When moderate to severe acne fails to respond to over-the-counter treatments, it may require prescription medications. Oral antibiotics are the standard treatment for moderate to severe acne to help fight inflammation and diminish bacteria. Oral antibiotics generally take six to eight weeks to work, according to the American Academy of Family Physicians.
Azithromycin
Azithromycin is an oral medication that may help to treat moderate to severe cases of acne. Azithromycin works by killing and preventing the spread of bacteria, says Drugs.com.
A study published in the Dermatology Online Journal found that taking 500 mg of azithromycin daily for eight weeks effectively treated moderate to severe acne in the majority of the 52 adolescents who participated in the study. The study was led by M.D. Spadola of the Department of Specialistic and Experimental Clinical Medicine, Division of Dermatology, University of Bologna, Italy.
Side effects of azithromycin may include constipation, headache and nausea.
Tetracycline
Oral tetracycline medications work to diminish inflammatory acne lesions called papules and pustules, according to the American Academy of Dermatology.
The average dose of tetracycline for moderate to severe acne ranges between 500 and 1,000 mg daily and may be lowered as the condition improves. Tetracycline therapy may continue on a longer-term basis at a low-dose to help prevent recurring breakouts. Adverse reactions may include vomiting, nausea and diarrhea.
Children younger than 8 should not take tetracycline, as it may hamper growth and discolor developing teeth.
Minocycline & Doxycycline
Minocycline and doxycycline are synthetic versions of tetracycline. These oral medications are prescribed to fight bacterial infections, including acne, according to the National Institutes of Health, or NIH.
Minocycline is sometimes prescribed when other oral antibiotics have failed to work. Doxycycline may also be effective for stubborn cases of moderate to severe acne. It may be especially helpful in treating inflammatory acne, notes AAD.
Side effects of these medications may include headaches, dizziness, nausea and diarrhea.
Isotretinoin
Moderate to severe cases of acne that are very resistant to other treatments may find success with oral istretinoin, according to the American Academy of Dermatology.
A study published in April 2006 of the Journal of the American Academy of Dermatology found that a low daily dose of isotretinoin, defined as 20 mg, effectively treated moderate acne with few severe side effects. The study was led by B. Amichai of the Huzot Clinic of Clalit Health Services, Ashkelon, Israel.
This highly effective medication has been known to cause a number of side effects, including sun sensitivity, impaired night vision, muscle pain and nosebleeds, notes the Mayo Clinic.
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