Hyperkalemia in an Elderly Patient Receiving Standard Doses of Trimethoprim-Sulfamethoxazol — Case Report and Brief Review of the Literature

Abstract

MA Al-Murayeh, CM Kjellstrand, Hyperkalemia in an Elderly Patient Receiving Standard Doses of TrimethoprimSulfamethoxazol -Case Report and Brief Review of the Literature. 1995; 15(4): 402-403 Trimethoprim sulfamethoxazole (Tmp-Smx) is a commonly used antimicrobial drug in the treatment of respiratory tract and urinary tract infections.Tmp-Smx has been in clinical use since 1968. 1 It may induce an isolated elevation of serum creatinine (pseudorenal failure), interstitial nephritis with acute renal failure 2-4 and mild hyperkalemia when used in patients with acquired immunodeficiency syndrome (AIDS).5 There have been rare case reports of dangerous hyperkalemia in patients receiving high doses of co-trimoxazole. 6 Recently, three elderly patients were reported to have developed hyperkalemia with standard doses of In this article we present the case history of a patient who developed moderate hyperkalemia while on regular dose Tmp-Smx and also a brief review of the literature on this topic to increase the awareness of this potentially lethal complication which may be under-recognized. Case ReportAn 89-year-old female fractured both her left hip and left humerus after a fall in her apartment. She underwent surgery and while an in-patient developed a symptomatic lower urinary tract infection caused by Escherichia coli, sensitive to both Tmp-Smx and ampicillin.Her serum chemistries on admission were Na 135 mmol/L, K 3.8 mmol/L, Cl 103 mmol/L, total C0 2 23.4 mmol/L, blood urea nitrogen (BUN) 5.1 mmol/L and creatinine 90 μmol/L Urinalysis on admission was normal. She was started on Tmp-Smx orally, one tablet twice a day. Each tablet consisted of trimethoprim 160 mg and sulfamethoxazole 800 mg.On the fourth day on Tmp-Smx her serum potassium increased to 5.8 mmol/L. This could not be explained on clinical grounds as she was not diabetic or hypertensive nor did she have renal failure. The patient was not on any known medication that might alter the potassium metabolism or homeostasis; there was no change in her diet and she was not dehydrated.Her serum chemistries were repeated on the sixth day and were as follows: Na 139 mmol/L, K 6.4 mmol/L, Cl 104 mmol/L, BUN 8.7 mmol/L, CO 2 22.5 mmol/L, creatinine 170 μmol/L. Urinalysis was unremarkable, there was no peripheral eosinophilia and clinically she continued to be afebrile and had no skin rashes. An electrocardiogram showed elevated and peaked T-waves.Tmp-Smx was discontinued and the patient was given kayexalate orally (30 g once) and 10 U of regular insulin in an intravenous drip of 500 mL dextrose 10%, infused over five hours. Serum potassium fell to 5.3 mmol/L and serum creatinine decreased to 120 μmol/L. During the week following discontinuation of Tmp-Smx, her serum potassium stabilized at 5.0 mmol/L and serum creatinine at 90 μmol/L. The clinical course of potassium and creatinine are demonstrated in Figure 1. DiscussionOur patient had mild acute renal failure and moderate hyperkalemia caused by Tmp-Smx. Hyperkalemia is not generally recognized as a complication...