Submitted by Dr LAU Chun Wing Arthur, ICU, PYNEH, Hong Kong, on 30 May 2009
An adult male patient of normal renal function and urine output was receiving co-trimoxazole (trimethoprim-sulphamethoxazole, septrin) for Xanthomonas maltophilia pneumonia. Three days later, his K level became 5.5 mmol/L. Na, Ur, Cr, urine output remain normal. Which is the most likely cause of the hyperkalaemia?
A. Xanthomonas maltophilia pyelonephritis
B. Trimethoprim
C. Sulphamethoxazole
D. Others
Answer: B
For this early onset of hyperkalaemia, it is likely due to the amiloride-like potassium-sparing properties of trimethoprim.
For sulfamethoxazole, the nephrotoxic reactions including interstitial nephritis and tubular necrosis, which may result in renal failure, have been attributed to hypersensitivity to sulfamethoxazole. Lumbar pain, haematuria, oliguria, and anuria may also occur due to crystallisation in the urine of sulfamethoxazole or its less soluble acetylated metabolite.
Xanthomonas maltophila has been reported to be a cause of pyelonephritis, but that was due to direct introduction from chronic urinary tract catheterization.
References
1. Martindale on trimethoprim, sulfamethoxazole
2. McDonald GR, Pernenkil R. Community-acquired Xanthomonas maltophilia pyelonephritis. South Med J. 1993 Aug;86(8):967-8.