Trimethoprim-sulfamethoxazole (TMP-SMX, Bactrim, Septra) can be used as prophylaxis for Pneumocystis carinii infection.
Oral formulations for TMP-SMX (in fixed dose ratio of 1 to 5):
(1) single strength tablet (80 mg TMP, 400 mg SMX)
(2) double strength tablet (DS, 160 mg TMP, 800 mg SMX)
(3) suspension (8 mg TMP per mL, 40 mg SMX per mL)
Prophylaxis in adults may include one of the following:
(1) 1 double strength tablet daily
(2) 1 single strength tablet daily
(3) 1 double strength tablet daily for 3 consecutive days per week
Prophylaxis in children:
(1) daily dose based on body surface area (BSA) 150 mg TMP per square meter BSA and 750 mg SMX per square meter BSA
(2) maximum daily dose is 320 mg TMP and 1600 mg SMX
(3) daily dose divided in 2 and given orally every 12 hours
(4) therapy is given on 3 consecutive days per week
Body Surface Area
Tablet every 12 hours
< 0.53 square meter
use liquid suspension
0.53 square meter
0.5 single strength
1.06 square meter
1.0 single strength
1.59 square meters
1.5 single strength
2.12 square meter
2.0 single strength or 1 double strength
Side effects are relatively common in patients receiving prophylaxis. Lower dose or 3 day per week regimens have a lower risk of complications.
TMP-SMX is contraindicated in infants < 2 months old.
If renal function is impaired, then the dose should be reduced.
> 30 mL per min
15 - 30 mL per min
reduce by 50%
< 15 mL per min
use alternative therapy
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Specialty: Infectious Diseases, Pharmacology, clinical