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Bactrim DS & Respiratory Infections

Bactrim DS contains 800 mg sulfamethoxazole and 160 mg trimethoprim. The DS signifies double strength compared to the regular strength (400 mg/80 mg). Both sulfamethoxazole and trimethoprim are antibiotics. The brand Septra also contains these ingredients. The U.S. Food and Drug Administration has approved Bactrim DS for two respiratory indications: acute exacerbation of chronic bronchitis in adults due to susceptible strains of bacteria, and prevention of pneumonia caused by Pneumocystis carinii in immuno-suppressed patients.

  1. Growing Resistance

    • The official prescribing information for Bactrim DS notes that it should be used only for infections known or likely to be caused by susceptible bacteria. A study by Ian Critchley published in the December 2007 issue of the journal Antimicrobial Agents and Chemotherapy found that up to 25 percent of the strains of Streptococcus pneumoniae and Haemophilus influenzae had resistance to Bactrim DS. Another study in the same journal by Pauliina Kärpänoja in July 2008 revealed that restricting Bactrim DS use can reduce the resistance rates of S. pneumoniae.

    Bronchitis

    • Bactrim DS treats flare-ups of chronic bronchitis in adults. This kind of bronchitis generally results from some non-infectious disease or constant exposure to an irritant such as tobacco smoke. The irritation can enable bacteria to infect the lungs. In such cases, an antibiotic can cure the infection but not the underlying irritation. According to a June 2009 article by Jazeela Fayyaz on Emedicine.com, Bactrim DS "remains a good and inexpensive choice" for treating this kind of bronchitis.

    P. Carinii Pneumonia Prevention

    • The National Institutes of Health guidelines for preventing pneumonia caused by P. carinii, updated in September 2009, refer to Bactrim DS as the "drug of choice" because of its clinical and cost effectiveness as well as its safety. P. carinii normally does not cause a problem, but in immuno-suppressed persons, such as those who have had a transplant or who are HIV-positive, it can colonize the lungs. Taken regularly, Bactrim DS will prevent such infections. The guidelines also recommend Bactrim DS when P. carinii infections actually occur.

    Dosing

    • Adults with acute exacerbation of chronic bronchitis should take one Bactrim DS tablet (or two tablets of the regular strength) every 12 hours for two weeks. For preventing P. carinii pneumonia, adults should take one Bactrim DS tablet daily. Generally children will take one-half to one tablet daily. For treating P. carinii pneumonia, the dose for both adults and children relates to body weight, taken every six hours for two to three weeks. Patients should take Bactrim DS for the full duration of treatment to completely eradicate the bacteria, otherwise resistant bacteria will develop.

    Safety

    • As with many antibiotics, the most common side effects of Bactrim DS pertain to the gastrointestinal system and include nausea, vomiting and anorexia. Allergic skin reactions can also occur. Certain rare but serious reactions have been reported. All reactions require immediate medical attention.

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