Triamterene-induced nephrolithiasis

Drug-Induced Kidney Stones and Crystalline Nephropathy: Pathophysiology, Prevention and Treatment

Drug-induced calculi represent 1-2% of all renal calculi. The drugs reported to produce calculi may be divided into two groups. The first one includes poorly soluble drugs with high urine excretion that favour crystallisation in the urine. Among them, drugs used for the treatment of patients with human immunodeficiency, namely atazanavir and other protease inhibitors, and sulphadiazine used for the treatment of cerebral toxoplasmosis, are the most frequent causes. Besides these drugs, about 20 other molecules may induce nephrolithiasis, such as ceftriaxone or ephedrine-containing preparations in subjects receiving high doses or long-term treatment. Calculi analysis by physical methods including infrared spectroscopy or X-ray diffraction is needed to demonstrate the presence of the drug or its metabolites within the calculi. Some drugs may also provoke heavy intra-tubular crystal precipitation causing acute renal failure. Here, the identification of crystalluria or crystals within the kidney tissue in the case of renal biopsy is of major diagnostic value. The second group includes drugs that provoke the formation of urinary calculi as a consequence of their metabolic effects on urinary pH and/or the excretion of calcium, phosphate, oxalate, citrate, uric acid or other purines. Among such metabolically induced calculi are those formed in patients taking uncontrolled calcium/vitamin D supplements, or being treated with carbonic anhydrase inhibitors such as acetazolamide or topiramate. Here, diagnosis relies on a careful clinical inquiry to differentiate between common calculi and metabolically induced calculi, of which the incidence is probably underestimated. Specific patient-dependent risk factors also exist in relation to urine pH, volume of diuresis and other factors, thus providing a basis for preventive or curative measures against stone formation.

Accurate stone analysis: the impact on disease diagnosis and treatment

This manuscript reviews the requirements for acceptable compositional analysis of kidney stones using various biophysical methods. High-resolution X-ray powder diffraction crystallography and Fourier transform infrared spectroscopy (FTIR) are the only acceptable methods in our labs for kidney stone analysis. The use of well-constructed spectral reference libraries is the basis for accurate and complete stone analysis. The literature included in this manuscript identify errors in most commercial laboratories and in some academic centers. We provide personal comments on why such errors are occurring at such high rates, and although the work load is rather large, it is very worthwhile in providing accurate stone compositions. We also provide the results of our almost 90,000 stone analyses and a breakdown of the number of components we have observed in the various stones. We also offer advice on determining the method used by the various FTIR equipment manufacturers who also provide a stone analysis library so that the FTIR users can feel comfortable in the accuracy of their reported results. Such an analysis on the accuracy of the individual reference libraries could positively influence the reduction in their respective error rates.

Secondary and miscellaneous urolithiasis. Medications, urinary diversions, and foreign bodies

Secondary stones, those with no "classic" cause, provide unusual diagnostic and treatment challenges to the urologist. Stones related to medications, to urinary diversions or augmentation, or to presence of foreign bodies within the urinary tract occur rarely. Nevertheless, they represent situations that may be corrected fully by appropriate conservative or procedural therapy, and therefore they must be included in the differential diagnosis of many patients who present with symptoms of urolithiasis.

The analysis of peculiar urinary (and other) calculi: an endless source of challenge

The exact composition of calculi is clinically important, but many specimens are not examined, with resultant loss of important information. We describe the incidence and nature of false stones, peculiar calculi and crystals growing on surprising materials. We studied 3100 calculi (97% urinary, 2% digestive and 1% others). Fourier transform infrared spectroscopy was used to identify calculi by detailed comparison with libraries of reference spectra. We also used UV-visible spectroscopy, nuclear magnetic resonance and gas chromatography-mass spectrometry for specific situations. Among 3100 calculi, 154 (5%) had an unusual composition; 101 specimens (3.3%) were false calculi or artifacts, 31 (1%) contained drugs or metabolites and 22 (0.7%) corresponded to crystallizations around other materials. The findings contribute to immediate patient management and to advances in scientific and medical knowledge. We conclude that the analysis of all calculi must be carried out, to determine their composition, and an efficient strategy must be used.

Medical therapy, calcium oxalate urolithiasis

The development of diagnostic protocols that identify specific risk factors for calcium oxalate nephrolithiasis has led to the formulation of directed medical regimens that are aimed at correcting the underlying metabolic disturbances. Initiation of these treatment programs has reduced markedly the rate of stone formation in the majority of patients who form stones. This article discusses the rationale that underlies the choice of medical therapy for the various pathophysiologic causes of calcium oxalate nephrolithiasis and the appropriate use of available medications.

Renal function in the elderly: results from the European Working Party on High Blood Pressure in the Elderly trial

Effects of antihypertensive treatment on renal function were analyzed in data from a prospective, double-blind investigation of 840 patients randomly assigned to placebo or to active treatment with a combination of triamterene and hydrochlorothiazide. Baseline serum creatinine levels were significantly and positively correlated to age, gender (higher in men), systolic blood pressure, and history of cardiovascular complications. During a five-year follow-up period, serum creatinine levels increased significantly in treated patients but not in placebo patients. Five patients died of renal causes (one in the placebo group, four in the treated group), and five patients dropped out of the study because of an increase in serum creatinine of more than 100% (four received active treatment). The incidence of renal complications in the hypertensive elderly is small. The current data do not support the hypothesis that renal deterioration can be prevented by antihypertensive treatment.

Physicochemical and structural studies of triamterene

It has been shown by several physicochemical techniques that the existence of different crystal forms of triamterene, as well as the crystalline products from different solvents with distinct differences in melting points, does not necessarily imply polymorphic crystal forms. The crystalline structure for triamterene is reported herein, revealing a N,N-dimethylformamide molecule and a water molecule within the crystal lattice. Triamterene crystallizes in a face-centered orthorhombic space group, Fdd2 (#43), when grown from aqueous solutions of dimethylformamide (N,N-DMF). In addition, the asymmetric unit contains a partially occupied molecule which is situated on a crystallographic twofold axis. Weak hydrogen bonding occurs between atoms O(1) and N(7), with a distance of 2.66 A, O(1) and N(5) with a distance of 2.96 A, O(2) and N(1), at two different symmetry sites of 2.99 A, and N(2) and N(7), with a distance of 2.91 A. The different solvated crystalline triamterene specimens have different melting points depending on organic solvation, water, or both.

Triamterene bladder calculus

A case report of triamterene bladder calculus is presented. Triamterene containing antihypertensives should be used with caution in patients with predisposition to form stones.

Triamterene and renal stone formation: the influence of triamterene and triamterene stones on calcium oxalate crystallization

A constant composition method has been used to compare the effects of triamterene renal stone material, synthetic triamterene precipitates, and soluble triamterene on the nucleation and crystallization kinetics of calcium oxalate in aqueous solution in vitro. Crystallization studies have been carried out with the concentrations of calcium and oxalate ions maintained constant by the potentiometrically controlled addition of concentrated reagent solutions containing these ions. Triamterene renal stones were found to be much less effective than synthetic triamterene towards promoting the nucleation and crystallization of calcium oxalate from supersaturated solution. Renal stones composed of triamterene and matrix did not significantly enhance the deposition of calcium oxalate compared to nonseeded controls. The triamterene stones were also found to be ineffective in promoting calcium oxalate crystallization compared to other precipitates thought to be involved in the etiology of stone disease such as calcium hydroxyapatite. For stones of mixed triamterene/calcium oxalate composition, the enhancement of the nucleation and crystallization of calcium oxalate was directly related to the calcium oxalate content of the stone seed material. The presence of soluble triamterene or its metabolites in solution did not influence the crystallization kinetics of pure calcium oxalate seed materials. The results of this study indicate that triamterene in stones does not significantly contribute to further stone development through the enhancement of calcium oxalate crystallization processes.

Etiopathogenesis of uncommon canine uroliths. Xanthine, carbonate, drugs, and drug metabolites

Metabolic disorders, medication, and diagnostic agents may be associated with urolithiasis in dogs. Examples of uroliths that have been uncommonly encountered in dogs include xanthine, dolomite, tetracycline, and sulfonamides. Detection of these and other apparently uncommon uroliths requires a high index of suspicion and proper methods of analysis.

Metabolic fate and solubility of triamterene--not an explanation for triamterene nephrolithiasis

In an attempt to explain the triamterene stone diathesis, we studied the excretion and solubility of triamterene, 1, and its metabolite, the sulfate ester of the hydroxy derivative of triamterene, 3. The urinary excretion pattern and metabolism in stone formers was the same as in other chronic users of triamterene or healthy volunteers. The solubility of triamterene in urine was approximately one-half of its solubility in buffer solution, whereas the sulfate ester, 3, was nearly twice as soluble in urine as in the buffer solution. In the majority of the subjects studied, we found concentrations of 3 which approached or exceeded apparent solubility limits in urine. This was not true for triamterene where most measured urine concentrations were less than the apparent solubility as determined by equilibration. Alteration in the metabolism of triamterene is probably not a causative factor for triamterene nephrolithiasis. The saturation of urine with triamterene and especially with the sulfate ester, 3, may be related to stone formation, but other physical factors play a role in determining the relative amounts of drug found in calculus material.

Triamterene stones and computerized axial tomography

A recently recognized entity in the differential diagnosis of radiolucent filling defects of the pyelocalyceal systems is triamterene calculus. A case is presented of a patient on triamterene therapy for hypertension in whom a symptomatic triamterene calculus formed which was diagnosed by computerized axial tomography.

The true composition of kidney stones passed during triamterene therapy

The potassium-sparing agent triamterene and its metabolites have been identified as components of kidney stones passed by patients receiving that drug. We have analyzed 66 such kidney stones by use of quantitative thin-layer chromatography. The stones contained not only the unchanged triamterene but also significant amounts of an intermediate metabolite, hydroxytriamterene, and large amounts of the sulfate ester of hydroxytriamterene. Of the stones 49 per cent contained less than 5 per cent triamterene and its metabolites, and no stone comprised 100 per cent triamterene-derived material. Of all the triamterene-related material unchanged triamterene dominated. However, the relative fractions of triamterene and hydroxytriamterene in the kidney stones exceeded the relative fractions of these 2 components in the urine.

Excretion of triamterene and its metabolite in triamterene stone patients

As triamterene users may form kidney stones containing deposits of triamterene and its metabolites, we studied urinary excretion to detect any altered metabolism of triamterene in these patients. We found no significant differences between patients and matched control subjects in total recovery, hourly excretion patterns, and concentrations of triamterene and its sulfate metabolite. Approximately half of all subjects tested revealed urine concentrations of the sulfate metabolite that exceeded the observed solubility limit.

Triamterene calculus

Triamterene therapy is an unusual cause of nephrolithiasis and, when this agent is found in a stone, generally it is deposited in minor amounts. We report a renal calculus consisting mostly of triamterene and its 2 major metabolites in a patient taking a triamterene-containing drug, and discuss some implications.

Sulphate conjugation of p-hydroxytriamterene by platelet phenol sulphotransferase: assay conditions and correlation with metabolism in man

1 Sulphate conjugation catalyzed by phenol sulphotransferase (PST) is an important pathway in the metabolism of many drugs including triamterene. Variations in PST activity in an easily obtained tissue such as the platelet might reflect individual differences in the sulphate conjugation in other organs and tissues. Human platelets contain at least two forms of PST, a thermolabile (TL) form for which dopamine is a substrate and a thermostable (TS) form for which low concentrations of p-nitrophenol serve as a substrate. 2 p-OH-triamterene, the major metabolite of triamterene, is conjugated with sulphate in vivo. p-OH-triamterene was a substrate for platelet PST with an apparent Michaelis-Menten value of 26 microM. Thermal stability studies indicated that p-OH-triamterene was a substrate for only the TS form of platelet PST. 3 When platelet homogenates from 29 individual subjects were tested, there was a significant correlation between PST activities measured with 4 microM p-nitrophenol and with p-OH-triamterene (r = 0.985, P less than 0.0001) but not between activities measured with dopamine and with p-OH-triamterene (r = 0.023, P greater than 0.2). These results confirmed that p-OH-triamterene was a substrate for only the TS form of human platelet PST. 4 The same 29 subjects were treated with 1 mg/kg of triamterene orally. 24-h urinary excretions of triamterene, p-OH-triamterene and p-OH-triamterene sulphate averaged 15.3%, 6.3% and 78.4%, respectively, of the total of triamterene plus measured metabolites excreted. The excretion of triamterene plus the two metabolites averaged 43.1 +/- 2.6% (mean +/- s.e. mean) of the ingested dose. There was not a significant correlation between the proportion of p-OH-triamterene excreted as sulphate conjugate and the activities of either the TS or TL forms of platelet PST activity.

Triamterene and renal stone formation

We investigated the influence of triamterene (TA), and its metabolites parahydroxytriamterene (PHTA), and parahydroxytriamterene sulfate (PHTAS) on the nucleation and crystal growth of calcium oxalate monohydrate (COM), in supersaturated solution at 37C using a new constant composition technique. The spontaneous precipitation of COM is preceded by induction periods which decrease with increasing supersaturation. The addition of the triamterene seed materials substantially reduces there delay periods and induces the crystal growth of COM. Specific surface area and scanning electron microscopic results indicate that the seed materials act as sources for the heterogeneous nucleation of COM. In addition, the surface of the more crystalline PHTAS appears to offer sites from which COM crystals can develop as well formed rosettes. This evidence suggests that in addition to triamterene renal stone formation, TA and its metabolites may catalyze the precipitation of other stone forming minerals with which urines may be supersaturated.

Triamterene stone: advantage of crystallographic analysis

Microscopic crystallographic analysis of renal calculi provides clinically useful information concerning the pathogenesis of stone disease and is, therefore, superior to conventional chemical analysis of stones. The advantages of crystallography, performed at a centralized, experienced stone-analysis center, are highlighted by the recent discovery of triamterene deposits in kidney stones. Deposits of other medications and their metabolites have also been uncovered. Two case reports are presented, the clinical implications of these and related findings are discussed.

Triamterene nephrolithiasis complicating dyazide therapy

A case of triamterene nephrolithiasis is reported in a man after 4 years of hydrochlorothiazide-triamterene therapy for hypertension. The stone passed spontaneously and was found to contain a triamterene metabolite admixed with uric acid salts. Factors affecting triamterene nephrolithiasis are discussed and 2 previously reported cases are reviewed.

Toxic nephropathy from diagnostic and therapeutic agents. Review and commentary

Drugs commonly used for diagnostic and therapeutic purposes may cause toxic nephropathy. There are several factors that account for renal susceptibility. Precise mechanisms of toxicity are generally not known, and therapy depends upon recognizing and removing the offending agent. Drugs that affect identifiable segments of the nephron or that produce similar syndromes are grouped together. Measures that might prevent toxicity are presented.