Many opportunistic infections can be prevented by using cotrimoxazole prophylaxis, particularly in the case of:

Indications for Prophylactic Treatment Using Cotrimoxazole

Prophylactic treatment using Cotrimoxazole should be provided if any of the following criteria apply:


For adults: One double-strength tablet (160/800 mg) or two single strength tablets once a day on a daily basis. For those weight is<60 kg.

Criteria for Stopping:

Follow up and Monitoring:



The fixed dose combination of trimethoprim and sulfamethoxazole is called cotrimoxazole.

Trimethoprim is a diaminopyrimidine which selectively inhibits bacterial dihydrofolate reductase (DHFRase).

Sulfamethoxazole is the Sulfonamides considered to be derivatives of p-aminobenzoic acid’(PABA) which are Intermediate acting (8-12 hours).

It has slower oral absorption and urinary excretion resulting in intermediate duration of action; half-life in adults average 10 hours. It is the preferred compound for combining with trimethoprim because the half-life of both is similar.

However, a high fraction is acetylated, which is relatively insoluble-crystalluria can occur.

Adverse effects: All adverse effects seen with sulfonamides can be produced by cotrimoxazole.

Cotrimoxazole should not be given during pregnancy. Trimethoprim being an antifolate, there is theoretical teratogenic risk. Neonatal haemolysis and methaemoglobinaemia can occur if it is given near term.


Through cotrimoxazole is still used, its popularity in the treatment of systemic infections has declined. Common indications are:

  1. Urinary tract infections: Most acute uncomplicated infections respond rapidly. Single dose therapy with 4 tablets of cotrimoxazole has been successfully for acute cystitis. Course of 3-10 days have been advised for lower and upper urinary tract infections, according to associated features. Cotrimoxazole is especially valuable for chronic or recurrent cases or in prostatis, because trimethoprim is concentrated in prostate.
  2. Respiratory tract infections: Both upper and lower respiratory tract infections, including chronic bronchitis and facia-maxillary infections, otitis media caused by gram positive cocci and influenzae respond well.
  3. Bacterial diarrheas and dysentery: Cotrimoxazole may be used for severe and invasive infections by coli, Shigella, nontyphoid Salmonella, and Y. enterocolitica. Though response rate is lower than previously, and fluoroquinolones are more commonly used, it is still a valuable alternative for empirical therapy of infective diarrhea.
  4. Pneumocystis jiroveci: Causes severe pneumonia in neutropenic and AIDS patients. Cotrimoxazole has prophylactic as well as therapeutic value, but high doses are needed.
  5. Chancroid: Cotrimoxazole (800+160 mg) BD for 14 days is a third choice, but less expensive, alternative to ceftriaxone, azithromycin or ciprofloxacin.
  6. Typhoid: Initially Cotrimoxazole was an effective alternative to chloramphenicol. However, it has become unreliable, and is seldom used now.
  7. Cotrimoxazole is an alternative to penicillin for protecting agranulocytosis patients and for treating respiratory or other infections in them. Intensive parenteral cotrimoxazole therapy has been used successfully in septicemias, but other drugs are commonly employed now.



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