Results

Of the 500 patients reviewed, 121 patients were excluded due to impaired renal function (GFR <60 mL/min/1.73 m2), 168 did not have follow-up data, and 50 patients received less than two doses of co-trimoxazole. One hundred sixty-one patients who fulfilled the inclusion criteria were included. Of these, 57.1% (n=92) were male and 57.1% (n=92) were prescribed other medications known to contribute to hyperkalemia. Around 24% of the patients had hypertension, 56% had diabetes, and 46% were status-post organ transplant. The patients were divided into two groups based on the co-trimoxazole (DS tablet 800/160 mg) dosing frequency; once daily vs. twice daily dosing regimen. The number of patients in each group was comparable (Table 1).
Hyperkalemia (potassium serum concentration >5.5 mEq/L) was observed in 46 (28.6%) patients, of whom, 25 (29 %) were in the twice-daily dosing group. Thirty-five (76.1%) of the patients who developed hyperkalemia were receiving concurrent medications known to increase potassium serum levels (Table 1). Receiving co-trimoxazole in combination with β-blockers, immunosuppressant agents alone or in combination with β-blockers was significantly associated with higher incidence of hyperkalemia when compared to receiving co-trimoxazole alone [OR 3.2, 95% CI (1.1-9.7), p=0.035, OR 3.2, 95% CI (1.2-8.3), p=0.019, OR 3.4, 95% CI (1.2-9.8), p=0.024] (Table 2). Moreover, patients with age >60 years were more prone to develop hyperkalemia when compared to younger age groups 18-39 years [OR 6.37, 95% CI (2.6-18.8), p=0.001]
[Please insert Table 1 here]
[Please insert Table 2 here]
After adjusting the confounders with the multivariate logistic regression analysis, only the following factors were found be significant. Patients with age >60 years were more prone to develop hyperkalemia when compared to the younger age groups 18-39 years [adjusted OR 6.5, 95% CI (2.1-19.7), p=0.001]. Moreover, the middle age group (40-60 years) was also found to have higher incidence of hyperkalemia than the younger age group 18-39 years [adjusted OR 3.5, 95% CI (1.2-10.5), p=0.023]. In addition, the co-administration of other medications that may induce hyperkalemia was found to be associated with higher incidence of hyperkalemia when compared to those receiving co-trimoxazole alone [adjusted OR 3.2, 95% CI (1.4-7.3), p=0.005].