MAXZIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MAXZIDE (MAXZIDE).
Maxzide is a combination of triamterene, a potassium-sparing diuretic that inhibits sodium reabsorption in the distal renal tubule, and hydrochlorothiazide, a thiazide diuretic that inhibits sodium and chloride reabsorption in the distal convoluted tubule. The combination reduces electrolyte disturbances.
| Metabolism | Triamterene is metabolized in the liver to active metabolites (hydroxytriamterene sulfate); hydrochlorothiazide is not extensively metabolized. |
| Excretion | Renal: triamterene and hydrochlorothiazide are primarily excreted by the kidneys. Triamterene is extensively metabolized; about 20-30% of the dose is excreted unchanged in urine, with additional metabolites. Hydrochlorothiazide is excreted unchanged in urine (at least 61% of an oral dose within 24 hours). |
| Half-life | Triamterene: terminal half-life is approximately 4-6 hours in healthy individuals, but may be prolonged in renal impairment. Hydrochlorothiazide: terminal half-life is approximately 6-15 hours, and it accumulates in renal dysfunction. The combination product's effective half-life is influenced by both components. |
| Protein binding | Triamterene: approximately 50-70% bound to plasma proteins. Hydrochlorothiazide: approximately 40-68% bound to plasma albumin. |
| Volume of Distribution | Triamterene: apparent Vd is about 1.5-2 L/kg. Hydrochlorothiazide: apparent Vd is about 3-4 L/kg, indicating extensive distribution into tissues. |
| Bioavailability | Oral bioavailability: triamterene is approximately 50-70% (with food may increase); hydrochlorothiazide is approximately 70-80%. Maxzide tablets have similar bioavailability to individual components. |
| Onset of Action | Oral: diuretic effect begins within 2 hours after administration, with peak effect at 4-6 hours for hydrochlorothiazide and triamterene. |
| Duration of Action | Duration of diuretic effect is approximately 12-16 hours after a single oral dose, but antihypertensive effects persist for up to 24 hours with continued dosing. |
Hydrochlorothiazide 25 mg / triamterene 37.5 mg orally once daily; may increase to twice daily if needed. Max dose: hydrochlorothiazide 50 mg / triamterene 75 mg daily.
| Dosage form | TABLET |
| Renal impairment | GFR 30-49 mL/min: use with caution; GFR <30 mL/min: contraindicated due to risk of hyperkalemia. |
| Liver impairment | Child-Pugh class A: no adjustment; Child-Pugh class B or C: contraindicated due to potential electrolyte disturbances and diuretic-induced hepatic encephalopathy. |
| Pediatric use | Not established; safety and efficacy in pediatric patients have not been determined. |
| Geriatric use | Initiate at lowest dose (hydrochlorothiazide 12.5 mg/triamterene 37.5 mg) and titrate slowly due to increased risk of electrolyte imbalance and renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MAXZIDE (MAXZIDE).
| Breastfeeding | Hydrochlorothiazide is excreted in breast milk at low levels (M/P ratio approximately 0.5-0.6). Triamterene is also excreted. Potential for neonatal electrolyte disturbances and diuresis. Not recommended during breastfeeding unless essential, with monitoring of infant serum electrolytes and hydration status. |
| Teratogenic Risk | MAXZIDE (triamterene/hydrochlorothiazide) is contraindicated in pregnancy. Thiazide diuretics cross the placenta and are associated with fetal or neonatal jaundice, thrombocytopenia, and electrolyte imbalances. First trimester use may increase risk of neural tube defects. Second and third trimester exposure may cause fetal hypotension, hyponatremia, hypokalemia, and decreased placental perfusion. |
■ FDA Black Box Warning
None
| Serious Effects |
["Hyperkalemia","Anuria","Acute or chronic renal insufficiency","Concomitant use with other potassium-sparing diuretics or potassium supplements","Hypersensitivity to triamterene, hydrochlorothiazide, or sulfonamide-derived drugs"]
| Precautions | ["Hyperkalemia risk, especially in patients with renal impairment, diabetes, or using other drugs that increase potassium","Monitor serum electrolytes, renal function, and blood glucose","May cause acute myopia and angle-closure glaucoma","Exacerbation or activation of systemic lupus erythematosus"] |
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| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (potassium, sodium, chloride, bicarbonate), renal function (BUN, creatinine), and uric acid. Fetal monitoring includes ultrasound for growth restriction and amniotic fluid volume assessment (risk of oligohydramnios). |
| Fertility Effects | No well-established effects on fertility. Thiazide diuretics may cause metabolic disturbances (e.g., electrolyte imbalances, hyperuricemia) that could theoretically affect reproductive function. Reversible with discontinuation. |