Triamterene

Triamterene capsules are approved to treat edema (fluid retention) caused by several different conditions. Both Dyrenium and Triamterene Capsules USP are approved for the same uses:

• Edema associated with congestive heart failure
• Edema associated with cirrhosis of the liver
• Edema associated with nephrotic syndrome (a kidney condition causing protein loss and swelling)
• Steroid-induced edema (fluid retention caused by corticosteroid medications)
• Idiopathic edema (fluid retention with no identified cause)
• Edema due to secondary hyperaldosteronism (excess production of a hormone that makes the body hold onto sodium and water)
• Used alone or combined with other diuretics for added fluid removal or to help preserve potassium levels
• May help patients who do not respond fully to thiazide or other diuretics because of secondary hyperaldosteronism

Triamterene works by blocking a specific sodium-potassium exchange in the distal tubule — a segment of the kidney's filtering tube. Normally, your kidneys reabsorb sodium (keeping it in your body) while flushing out potassium. Triamterene stops that trade: sodium and water leave through urine, and potassium stays behind. Importantly, this effect happens directly on kidney tissue and does not depend on the hormone aldosterone — which makes it different from spironolactone, another potassium-sparing diuretic.

Because only a relatively small portion of filtered sodium reaches the part of the kidney where triamterene acts, the diuretic effect is modest on its own. Combining it with a more proximally acting diuretic (one that acts earlier in the kidney) increases both the fluid removed and the potassium-sparing benefit.

Triamterene capsules are taken by mouth, generally twice a day after meals. Taking it with food helps reduce stomach upset. Your prescriber will start you at an appropriate dose and adjust it based on how you respond. If you are also taking another diuretic or blood pressure medication, your doctor will likely start both at a lower dose and adjust from there.

• Always take it after meals unless your doctor says otherwise
• Do not stop potassium supplements on your own — your doctor will tell you if you need to discontinue them when starting triamterene
• Follow your prescriber's instructions closely; do not change your dose without talking to them first

Most side effects with triamterene are uncommon, but it's helpful to know what to watch for. Common side effects include:

• Nausea, vomiting, or diarrhea
• Weakness or fatigue
• Dizziness
• Headache
• Dry mouth
• High potassium levels (hyperkalemia)
• Rash or sensitivity to sunlight (photosensitivity)

More serious reactions — including severe allergic reactions (anaphylaxis), kidney problems (including kidney stones or acute kidney failure), liver abnormalities, and blood disorders — are rare but require immediate medical attention. If you notice muscle weakness, irregular heartbeat, yellowing of the skin or eyes, or signs of an allergic reaction, contact your doctor right away.

• High potassium (hyperkalemia): This is the most critical risk. Potassium can build up to dangerous levels, especially if you have kidney disease, diabetes, or are older or seriously ill. Untreated hyperkalemia can cause fatal heart rhythm problems. Your potassium levels must be checked regularly.
• Kidney function monitoring: Regular blood tests (BUN, creatinine, and potassium) are needed to make sure your kidneys are handling the medication safely.
• Do not combine with other potassium-sparing drugs: Using triamterene with spironolactone or amiloride is dangerous and contraindicated. Two deaths have been reported from this combination.
• Allergic and rare reactions: Blood disorders, liver damage, and serious allergic reactions have been reported rarely. Report any unusual symptoms to your doctor promptly.
• Diabetes: Triamterene may raise blood sugar levels. People with diabetes may need their diabetes medication adjusted.

Triamterene interacts with several medications and substances — always share your full medication list with your prescriber and pharmacist.

• Lithium — triamterene can raise lithium levels dangerously; close monitoring is required
• NSAIDs (like ibuprofen, naproxen, indomethacin) — may cause acute kidney failure when combined with triamterene; use with caution
• ACE inhibitors (blood pressure drugs like lisinopril) — increase the risk of high potassium levels
• Other potassium-sparing diuretics (spironolactone, amiloride) — must NOT be combined; potentially life-threatening
• Potassium supplements, salt substitutes, or low-salt milk — can push potassium to dangerous levels; avoid unless specifically directed by your doctor
• Blood pressure medications and other diuretics — effects may be intensified; dose adjustments may be needed
• Chlorpropamide (a diabetes medication) — combined use may cause severely low sodium levels
• Stored blood — high potassium content in stored blood can worsen hyperkalemia risk

This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.

• Tell your doctor if you have kidney disease — severe or worsening kidney dysfunction is a contraindication, with a possible exception for nephrotic syndrome
• Tell your doctor if you have severe liver disease — this is also a contraindication
• Tell your doctor if you have diabetes — you are at higher risk for high potassium, and blood sugar control may be affected
• Tell your doctor if you are older — elderly patients are more vulnerable to potassium buildup and kidney effects
• Do not take triamterene if you already have elevated potassium levels or azotemia (excess waste products in the blood from poor kidney function)
• Do not take if you are unable to urinate (anuria) — triamterene is contraindicated in anuria
• Tell your doctor if you are pregnant or planning to become pregnant — routine diuretic use in pregnancy is generally not recommended, though there may be specific situations where it's appropriate; discuss with your doctor
• Stop all potassium supplements and potassium-containing salt substitutes before or when starting triamterene, unless your doctor advises otherwise
• Tell your doctor if you have a known allergy to triamterene or any of its ingredients

Taking too much triamterene would most likely cause an imbalance in electrolytes, particularly dangerously high potassium, along with possible nausea, vomiting, stomach upset, weakness, and low blood pressure. There is no specific antidote. If an overdose is suspected, immediate medical attention is needed — treatment involves clearing the stomach, carefully monitoring electrolytes and fluid balance, and supportive care.

Triamterene reduces sodium reabsorption in the kidney's distal tubule, leading to increased sodium and water excretion in urine while potassium is retained. The diuretic effect typically begins within 2 to 4 hours of taking a dose, and most patients notice a response within the first day of treatment — though maximum benefit may take several days to develop. The duration of diuresis generally tapers off about 7 to 9 hours after administration, though this varies depending on kidney function. Because triamterene does not cause excessive loss of acids, it does not typically lead to alkalosis (a rise in blood pH seen with some other diuretics).

Triamterene is rapidly absorbed when taken by mouth, though somewhat less than half of the oral dose makes it into the bloodstream. Peak blood levels in healthy people occur around 3 hours after a dose. It is primarily broken down (metabolized) in the body into a compound called the sulfate conjugate of hydroxytriamterene, which is the main form found in the blood and urine. About 21% of the dose is recovered in urine over 48 hours. Although triamterene is about 67% bound to proteins in the blood, dialysis may still provide some benefit in cases of serious overdose.

Store at 25°C (77°F); excursions permitted to 15° - 30°C (59° - 86°F) . Dispense in a tight, light resistant container.