- Gary C Curhan, MD, ScD
Gary C Curhan, MD, ScD
- Section Editor — Chronic Kidney Disease
- Professor of Medicine
- Harvard Medical School
Triamterene is a potassium-sparing diuretic that is commonly used in the treatment of hypertension in combination with a thiazide diuretic. It is not widely appreciated, however, that triamterene is a potential nephrotoxin, occasionally inducing crystalluria and cast formation, and rarely causing stone formation or reversible acute kidney injury [1,2].
CRYSTALLURIA AND CAST FORMATION
Triamterene can induce the formation of both triamterene crystals (which are usually brown in color, spherical, and appear as a "Maltese cross" under polarized light) and granular casts (which can look identical to brown pigmented casts), at least when used in higher doses. The following studies illustrate this effect:
●In a study of 20 healthy adults who ingested 100 mg of triamterene, all 20 excreted triamterene crystals, and 17 out of 20 excreted granular casts, which were present within 11 hours of taking the drug . Alkalinization of the urine to a pH of 7.5 or higher prevented the appearance of crystals.
●In a study of 26 hypertensive patients given 50 mg of triamterene, crystals and casts were seen in 14 (54 percent) .
Whether crystals and casts commonly occur with 37.5 mg of triamterene (a more typical dose) is unknown. The mechanism responsible for the cast formation is unclear but appears to be specific to triamterene, as this finding is not seen with amiloride, another potassium-sparing diuretic [3,4].
- Sica DA, Gehr TW. Triamterene and the kidney. Nephron 1989; 51:454.
- Perazella MA. Crystal-induced acute renal failure. Am J Med 1999; 106:459.
- Fairley KF, Woo KT, Birch DF, et al. Triamterene-induced crystalluria and cylinduria: clinical and experimental studies. Clin Nephrol 1986; 26:169.
- Spence JD, Wong DG, Lindsay RM. Effects of triamterene and amiloride on urinary sediment in hypertensive patients taking hydrochlorothiazide. Lancet 1985; 2:73.
- Woolfson RG, Mansell MA. Does triamterene cause renal calculi? BMJ 1991; 303:1217.
- Carr MC, Prien EL Jr, Babayan RK. Triamterene nephrolithiasis: renewed attention is warranted. J Urol 1990; 144:1339.
- Sabot JF, Bornet CE, Favre S, Sabot-Gueriaux S. The analysis of peculiar urinary (and other) calculi: an endless source of challenge. Clin Chim Acta 1999; 283:151.
- Ettinger B, Oldroyd NO, Sörgel F. Triamterene nephrolithiasis. JAMA 1980; 244:2443.
- Sörgel F, Ettinger B, Benet LZ. The true composition of kidney stones passed during triamterene therapy. J Urol 1985; 134:871.
- Daudon M, Jungers P. Drug-induced renal calculi: epidemiology, prevention and management. Drugs 2004; 64:245.
- Matlaga BR, Shah OD, Assimos DG. Drug-induced urinary calculi. Rev Urol 2003; 5:227.
- Favre L, Glasson P, Vallotton MB. Reversible acute renal failure from combined triamterene and indomethacin: a study in healthy subjects. Ann Intern Med 1982; 96:317.
- Weinberg MS, Quigg RJ, Salant DJ, Bernard DB. Anuric renal failure precipitated by indomethacin and triamterene. Nephron 1985; 40:216.
- Nasr SH, Milliner DS, Wooldridge TD, Sethi S. Triamterene crystalline nephropathy. Am J Kidney Dis 2014; 63:148.