The aim of our study was to examine the primary prophylactic effect of sulfamethoxazole/trimethoprim single strength (SMZ/TM SS) against Pneumocystis jirovecii pneumonia (PCP) in connective tissue disease (CTD) patients with immune dysfunction induced by the long-term use of prednisolone. Prevalence of adverse drug reactions (ADRs) to sulfonamide in these patients was the secondary outcome.
This was a retrospective cohort study. Medical records of CTD patients who were treated with prednisolone ≥20 mg per day or equivalent doses of corticosteroid for more than 2 weeks and were followed for at least 12 weeks after receiving this dosage of corticosteroids at the Rheumatology clinic of Ramathibodi Hospital between October 2006 and September 2007 were reviewed. Information regarding clinical status, laboratory features, and clinical course of the enrolled subjects was recorded.
There were 138 episodes of PCP risk in 132 CTD patients; 59 episodes received SMZ/TM SS, while 79 episodes did not. All 6 PCP cases developed in patients without prophylaxis with an overall incidence of 4.3%. The incidence of PCP between the 2 groups was significantly different (P = 0.038). Absolute risk reduction and relative risk reduction were 7.3% and 100%, respectively. All ADR developed in 5 systemic lupus erythematosus patients (8.5%): 4 had drug rashes and 1 had mild hepatitis. There was no correlation between the use of, or allergic reactions to, SMZ/TM and lupus flare.
Sulfamethoxazole/trimethoprim single strength can be used effectively as a primary prophylaxis against PCP in high-risk CTD patients. Only mild ADR developed at this dosage. Further evaluations in larger groups of CTD patients are warranted.