Severe acne doesn't always respond to the first medication you try. Your dermatologist may need to prescribe several different types of medicines before you find one that works to help clear your skin. Some physicians use the oral antibiotics sulfamethoxazole and trimethoprim together--sold under the brand name Purbac in some countries, and brands including Bactrim and Septra in the U.S.--to treat bad acne that has failed to respond to other antibiotics.
Almost everyone gets acne, usually as teenagers when your awakening hormones also awaken your skin's sebaceous glands, which manufacture the oil for your skin, according to the Cleveland Clinic. Too much of that oil can bock your hair follicles, creating plugs that turn into small pimples. If bacterial infection sets in, smaller pimples can become inflamed, and additional blocked follicles will become pimples.
Purbac combines the active ingredients trimethoprim and sulfamethoxazole into an oral sulfa drug that treats the bacterial infection in acne, according to the National Library of Medicine's online drugs database. Physicians also prescribe it to treat urinary tract infections and pneumonia. The medication comes in both tablet and liquid forms, and in most cases, you'll take it twice per day. You should take it with a full glass of water each time.
Purbac and other antibiotics cause nausea, vomiting and stomach upset in some patients who take them, according to Drugs.com. If you experience these while taking the medication for your acne, talk with your physician about them. In addition, a very small minority of patients experience serious side effects from Purbac, including fever, sore throat and a headache combined with a skin rash. If you have any sign of a skin rash while taking the medication, no matter how minor, you should contact your physician immediately.
Medical research studies show that drugs with Purbac's combination of sulfamethoxazole and trimethoprim can effectively treat acne when other forms of antibiotics have failed. In a study published in the journal "Dermatologica" in 1978, clinicians treated 42 patients with sulfamethoxazole and trimethoprim, all of whom had acne that had become resistant to tetracycline antibiotics. A total of 79 percent of patients reported excellent results or complete resolution of their acne at the end of 18 weeks of treatment.
If you need an oral antibiotic, dermatologists generally start with erythromycin or a tetracycline, such as minocycline and doxycycline. Physicians generally reserve sulfamethoxazole-trimethoprim antibiotics such as Purbac for cases where the skin condition stops responding to the more commonly used drugs. In addition, you may need to use a topical prescription or over-the-counter medication in addition to Purbac to completely clear your skin.