DYRENIUM
Clinical safety rating: caution
Comprehensive clinical and safety monograph for DYRENIUM (DYRENIUM).
Potassium-sparing diuretic; competitively inhibits sodium reabsorption in the distal renal tubule, reducing sodium-potassium exchange and increasing sodium and chloride excretion while retaining potassium.
| Metabolism | Hepatic metabolism, primarily via hydroxylation and sulfation; undergoes enterohepatic circulation. |
| Excretion | Primarily renal (hepatic metabolism to active metabolites, then renal excretion); approximately 50% of the dose is excreted unchanged in urine; minor biliary/fecal elimination. |
| Half-life | Terminal elimination half-life approximately 24-72 hours (average 48 hours), prolonged in renal impairment; clinical context: supports once-daily dosing, but accumulation may occur with repeated dosing. |
| Protein binding | Approximately 80-90% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Vd approximately 0.5-1.5 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: approximately 50% (range 30-70%) due to first-pass metabolism. |
| Onset of Action | Oral: diuresis begins within 2-4 hours; peak effect at 6-12 hours. |
| Duration of Action | Oral: diuretic effect lasts 12-24 hours; antihypertensive effect persists with regular dosing. |
Oral: 100 mg twice daily. Maximum: 300 mg/day.
| Dosage form | CAPSULE |
| Renal impairment | CrCl 50-90 mL/min: reduce dose by 50%; CrCl <50 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: reduce dose by 50%; Child-Pugh B or C: contraindicated. |
| Pediatric use | Not recommended for children (safety and efficacy not established). |
| Geriatric use | Start at 50 mg twice daily; monitor electrolytes and renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for DYRENIUM (DYRENIUM).
| Breastfeeding | Triamterene is excreted in human milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. Data on effects on nursing infants are limited. caution is advised; consider alternatives, especially in neonates or high-risk infants due to potential for electrolyte imbalances. |
| Teratogenic Risk | DYRENIUM (triamterene) is a potassium-sparing diuretic. There are no adequate and well-controlled studies in pregnant women. Triamterene has been shown to cross the placental barrier in animals. Potential risks include electrolyte imbalances (hyperkalemia, hyponatremia) in the fetus. Use during pregnancy only if clearly needed. First trimester: Risk cannot be ruled out; avoid if possible due to potential effects on organogenesis. Second and third trimesters: May cause electrolyte disturbances in the fetus/newborn; use with caution. |
■ FDA Black Box Warning
None.
| Serious Effects |
["Hyperkalemia","Anuria","Severe renal impairment (CrCl <10 mL/min)","Concomitant use with potassium supplements or other potassium-sparing diuretics","Hypersensitivity to triamterene"]
| Precautions | ["Hyperkalemia risk, especially in patients with renal impairment, diabetes, or those taking ACE inhibitors/ARBs","Electrolyte imbalances (hyponatremia, hypomagnesemia)","Metabolic acidosis","May cause photosensitivity; caution with sun exposure"] |
| Food/Dietary | Avoid high-potassium foods (bananas, oranges, tomatoes, spinach, potatoes, avocados) and salt substitutes containing potassium chloride. Grapefruit juice may increase potassium levels; limit intake. Alcohol may increase dizziness. |
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| Fetal Monitoring | Monitor serum electrolytes (potassium, sodium, chloride) and renal function regularly. Assess fetal growth and amniotic fluid volume via ultrasound due to potential for reduced placental perfusion. Monitor for signs of hyperkalemia (ECG changes, muscle weakness) in both mother and neonate. Blood pressure monitoring is recommended. |
| Fertility Effects | Triamterene has no known direct effects on human fertility. However, diuretic use may cause electrolyte disturbances that could theoretically affect reproductive function. Animal studies have not shown impaired fertility at clinically relevant doses. |
| Clinical Pearls | Monitor serum potassium closely, especially in patients with renal impairment or on ACE inhibitors/ARBs. Avoid use in severe hepatic disease due to risk of hyperkalemia. May cause photosensitivity; advise sun protection. Onset of diuresis is 2-4 hours after oral dose. Not effective for hypertension monotherapy; typically used with thiazide or loop diuretics. |
| Patient Advice | Take exactly as prescribed; do not double doses. · Avoid potassium supplements and salt substitutes containing potassium. · Report muscle weakness, palpitations, or fatigue immediately. · Protect skin from sunlight; use sunscreen and protective clothing. · May cause dizziness; avoid driving if affected. · Maintain adequate fluid intake unless restricted by your doctor. |