"What are diuretics and how do they work?
The amount of fluid (water) retained by the body is controlled primarily by the kidneys. This occurs due to the kidney's ability to control the retention and elimination of sodium and chlorid"...
Abnormal elevation of serum potassium levels (greater than or equal to 5.5 mEq/liter) can occur with all potassium-sparing agents, including Dyrenium (triamterene). Hyperkalemia is more likely to occur in patients with renal impairment and diabetes (even without evidence of renal impairment), and in the elderly or severely ill. Since uncorrected hyperkalemia may be fatal, serum potassium levels must be monitored at frequent intervals especially in patients receiving Dyrenium (triamterene), when dosages are changed or with any illness that may influence renal function.
There have been isolated reports of hypersensitivity reactions; therefore, patients should be observed regularly for the possible occurrence of blood dyscrasias, liver damage or other idiosyncratic reactions.
Periodic BUN and serum potassium determinations should be made to check kidney function, especially in patients with suspected or confirmed renal insufficiency. It is particularly important to make serum potassium determinations in elderly or diabetic patients receiving the drug; these patients should be observed carefully for possible serum potassium increases.
If hyperkalemia is present or suspected, an electrocardiogram should be obtained. If the ECG shows no widening of the QRS or arrhythmia in the presence of hyperkalemia, it is usually sufficient to discontinue Dyrenium (triamterene) and any potassium supplementation, and substitute a thiazide alone. Sodium polystyrene sulfonate (Kayexalate®‚ Sanofi Synthelabo) may be administered to enhance the excretion of excess potassium. The presence of a widened QRS complex or arrhythmia in association with hyperkalemia requires prompt additional therapy. For tachyarrhythmia, infuse 44 mEq of sodium bicarbonate or 10 mL of 10% calcium gluconate or calcium chloride over several minutes. For asystole, bradycardia or A-V block transvenous pacing is also recommended.
The effect of calcium and sodium bicarbonate is transient and repeated administration may be required. When indicated by the clinical situation, excess K+ may be removed by dialysis or oral or rectal administration of Kayexalate®. Infusion of glucose and insulin has also been used to treat hyperkalemia.
Dyrenium (triamterene) tends to conserve potassium rather than to promote the excretion as do many diuretics and, occasionally, can cause increases in serum potassium which, in some instances, can result in hyperkalemia. In rare instances, hyperkalemia has been associated with cardiac irregularities.
Electrolyte imbalance often encountered in such diseases as congestive heart failure, renal disease or cirrhosis may be aggravated or caused independently by any effective diuretic agent including Dyrenium (triamterene) . The use of full doses of a diuretic when salt intake is restricted can result in a low-salt syndrome.
Triamterene can cause mild nitrogen retention, which is reversible upon withdrawal of the drug, and is seldom observed with intermittent (every-other-day) therapy.
By the very nature of their illness, cirrhotics with splenomegaly sometimes have marked variations in their blood. Since triamterene is a weak folic acid antagonist, it may contribute to the appearance of megaloblastosis in cases where folic acid stores have been depleted. Therefore, periodic blood studies in these patients are recommended. They should also be observed for exacerbations of underlying liver disease.
Triamterene has been reported in renal stones in association with other calculus components. Dyrenium (triamterene) should be used with caution in patients with histories of renal stones.
Carcinogenesis: In studies conducted under the auspices of the National Toxicology Program, groups of rats were fed diets containing 0, 150, 300 or 600 ppm of triamterene, and groups of mice were fed diets containing 0, 100, 200 or 400 ppm triamterene. Male and female rats exposed to the highest tested concentration received triamterene at about 25 and 30 mg/kg/day, respectively. Male and female mice exposed to the highest tested concentration received triamterene at about 45 and 60 mg/kg/day, respectively.
There was an increased incidence of hepatocellular neoplasia (primarily adenomas) in male and female mice at the highest dosage level. These doses represent 7.5X and 10X the Maximum Recommended Human Dose (MRHD) of 300 mg/kg/day (or 6 mg/kg/day based on a 50 kg patient) for male and female mice, respectively, when based on body weight and 0.7X and 0.9X the MRHD when based on body-surface area.
Although hepatocellular neoplasia (exclusively adenomas) in the rat study was limited to triamterene-exposed males, incidence was not dosedependent and there was no statistically significant difference from control incidence at any dose level.
Mutagenesis: Triamterene was not mutagenic in bacteria (Salmonella typhimurium strains TA98, TA100, TA1535 or TA1537) with or without metabolic activation. It did not induce chromosomal aberrations in Chinese hamster ovary (CHO) cells in vitro with or without metabolic activation, but it did induce sister chromatid exchanges in CHO cells in vitro with and without metabolic activation.
Impairment of Fertility: Studies of the effects of triamterene on animal reproductive function have not been conducted.
Pregnancy: Category C
Teratogenic Effects: Reproduction studies have been performed in rats at doses as high as 20 times the Maximum Recommended Human Dose (MRHD) on the basis of body weight, and 6 times the MRHD on the basis of body-surface area, without evidence of harm to the fetus due to triamterene. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
Nonteratogenic Effects: Triamterene has been shown to cross the placental barrier and appear in cord blood. The use of triamterene in pregnant women requires that the anticipated benefits be weighed against possible hazards to the fetus. These possible hazards include adverse reactions which have occurred in the adult.
Nursing Mothers: Triamterene has not been studied in nursing mothers. Triamterene appears in animal milk and is likely present in human milk. If use of the drug product is deemed essential, the patient should stop nursing.
Pediatric Use: Safety and effectiveness in pediatric patients have not been established.
Last reviewed on RxList: 5/28/2008
This monograph has been modified to include the generic and brand name in many instances.
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