‘More is not better’ may be the case with trimethoprim/sulfamethoxazole (TMP/SMX) Pneumocystis prophylaxis (PCP) (J Pediatr 2014; 164: 389-92).  This study indicates that a single-day course of TMP/SMX prophylaxis is as effective as other regimens.

Design: Prospective survey of 20 centers with newly diagnosed cancer between 2009-2011.  This included 1093 with solid tumors and 1373 with leukemia/lymphoma.  55.6% received 3-day/week prophylaxis, 16.5% received 2-day/week regimen, and 27.9% received 1-day/week regimen (5-10 mg/kg/day into 2 doses).

Key result:

• Incidence of PCP at 3 years was 0.09% overall.  The two cases occurred in the 2-day regimen (though both had withdrawn from treatment)

The authors note the need for PCP prophylaxis has been questioned for solid tumor patients.  However, the lack of PCP among the 439  children with leukemia/lymphoma indicates that a single day per week regimen is effective.

Bottomline: In GI/liver patients who need TMP/SMX prophylaxis, 1-day per week regimen is likely effective (as it is in leukemia/lymphoma patients).  One-day/week is easier and should help with compliance, which is the key to preventing PCP.