HYDROPRES 25
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HYDROPRES 25 (HYDROPRES 25).
Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing sodium and water reabsorption. Reserpine depletes catecholamines from central and peripheral nerve terminals by inhibiting vesicular monoamine uptake, leading to decreased sympathetic outflow.
| Metabolism | Hydrochlorothiazide is not metabolized; reserpine is extensively metabolized in the liver via hydrolysis and conjugation. |
| Excretion | Renal: hydrochlorothiazide 70% unchanged, reserpine ~30% unchanged; fecal: reserpine ~60% metabolites |
| Half-life | Hydrochlorothiazide: 6-15 hr; reserpine: 50-100 hr (terminal, with prolonged adrenergic depletion lasting days) |
| Protein binding | Hydrochlorothiazide: ~68% bound to albumin; reserpine: ~96% bound to albumin and alpha-1-acid glycoprotein |
| Volume of Distribution | Hydrochlorothiazide: ~3.6 L/kg (extensive tissue distribution); reserpine: ~5-10 L/kg (large Vd due to lipid solubility and tissue binding) |
| Bioavailability | Oral: hydrochlorothiazide ~65-72%; reserpine ~40-50% (extensive first-pass metabolism) |
| Onset of Action | Oral: hydrochlorothiazide diuresis within 2 hr; reserpine hypotension weeks for full effect |
| Duration of Action | Hydrochlorothiazide: 6-12 hr; reserpine: prolonged (days to weeks) due to irreversible vesicular monoamine transporter binding |
1 tablet orally once daily, each tablet contains hydrochlorothiazide 25 mg and reserpine 0.125 mg. Dosage may be increased to 2 tablets daily if needed.
| Dosage form | TABLET |
| Renal impairment | eGFR 30-60 mL/min: reduce dose to 1 tablet every other day. eGFR <30 mL/min: contraindicated due to hydrochlorothiazide component. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B or C: avoid use due to reserpine's potential for precipitating hepatic encephalopathy. |
| Pediatric use | Not recommended for pediatric use; safety and efficacy not established. |
| Geriatric use | Initiate at half the adult dose (0.5 tablet orally once daily) and titrate slowly, monitoring for hypotension, electrolyte imbalance, and CNS depression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HYDROPRES 25 (HYDROPRES 25).
| Breastfeeding | Hydrochlorothiazide and reserpine are excreted into breast milk. M/P ratio unknown. Thiazides can suppress lactation; reserpine may cause respiratory depression, bradycardia, and hypothermia in neonates. Use contraindicated during breastfeeding. |
| Teratogenic Risk | Pregnancy Category D. First trimester: Increased risk of fetal malformations (cardiovascular, CNS). Second/third trimesters: Fetal/neonatal hypotension, renal dysfunction, oligohydramnios, skull ossification defects, and death from hypotension/hyperkalemia. |
■ FDA Black Box Warning
Reserpine may cause mental depression and is contraindicated in patients with a history of depression, especially with suicidal tendencies.
| Serious Effects |
["Anuria","Sulfonamide allergy (hydrochlorothiazide)","History of depression or suicidal tendency (reserpine)","Active peptic ulcer","Ulcerative colitis","Electroconvulsive therapy","Hypersensitivity to any component"]
| Precautions | ["Electrolyte imbalance (hypokalemia, hyponatremia, hypomagnesemia)","Hyperuricemia","Sulfonamide allergy cross-sensitivity","Depression, especially at higher doses of reserpine","Bradycardia and arrhythmias","Exacerbation of systemic lupus erythematosus"] |
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| Fetal Monitoring |
| Maternal: Blood pressure, serum electrolytes (especially potassium, sodium), renal function, uric acid, and blood glucose. Fetal: Ultrasound for oligohydramnios, growth restriction, and fetal heart rate monitoring if used in third trimester. Neonatal: Observe for hypotension, electrolyte disturbances, and respiratory depression. |
| Fertility Effects | Reserpine can cause galactorrhea and gynecomastia due to prolactin elevation. Hydrochlorothiazide may rarely cause reversible erectile dysfunction. Both drugs have no direct effect on ovulation or spermatogenesis. |