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 |
| Molecular Weight | Hydrochlorothiazide: 297.74 Da; Reserpine: 608.68 Da. HYDROPRES 25 contains hydrochlorothiazide 25 mg and reserpine 0.125 mg, so combined molecular weight not applicable. Individual values: 297.74 and 608.68 Da. |
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 | Contraindicated: Risk of fetal hypotension, renal impairment, and oligohydramnios. ACE inhibitor effect with hydrochlorothiazide component further increases risk during first trimester. |
| 2nd trimester | Contraindicated: Fetal toxicity including oligohydramnios, skull ossification defects, and renal dysfunction reported. Hydrochlorothiazide may cause neonatal thrombocytopenia. |
| 3rd trimester | Contraindicated: High risk of neonatal hypotension, anuria, hyperkalemia, and intracranial hemorrhage. May cause electrolyte imbalances in neonate. |
Clinical note
Comprehensive clinical and safety monograph for HYDROPRES 25 (HYDROPRES 25).
| Placental transfer | Both components cross the placenta. Hydrochlorothiazide reaches fetal serum levels similar to maternal; reserpine accumulates in fetal tissues with potential for adverse effects. |
| Breastfeeding | Hydrochlorothiazide and reserpine are excreted into breast milk. May suppress lactation and cause adverse effects in nursing infants such as galactorrhea, lethargy, and electrolyte disturbances. Use only if essential and monitor infant for signs of hypotension. |
■ 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 |
Hypersensitivity to hydrochlorothiazide, reserpine, or sulfonamidesAnuriaRenal impairment (creatinine clearance <30 mL/min)Hepatic coma or pre-comaActive peptic ulcer or ulcerative colitisElectroconvulsive therapy (within 7 days)PheochromocytomaConcurrent use with MAOIsHistory of mental depression (especially with suicidal tendencies)Pregnancy (all trimesters)
| 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 |
| Food/Dietary | Avoid excessive intake of tyramine-rich foods (aged cheeses, cured meats, fermented products) due to risk of hypertensive crisis if reserpine acts as a monoamine depleter. Limit alcohol. Maintain adequate fluid intake; avoid high-sodium foods which can counteract antihypertensive effect. |
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| Lactation Rating | L4 (Possibly Hazardous) |
| 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. |
| 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. |
| Clinical Pearls | HYDROPRES 25 is a fixed-dose combination of hydrochlorothiazide 25 mg and reserpine 0.125 mg. Reserpine depletes catecholamines, causing delayed onset (2-3 weeks) of maximal antihypertensive effect. Monitor for depression, nasal congestion, and bradycardia. Avoid in patients with history of major depression, peptic ulcer, or pheochromocytoma. Hydrochlorothiazide may cause electrolyte disturbances; monitor potassium. |
| Patient Advice | Take exactly as prescribed, usually once daily; do not discontinue abruptly. · May cause dizziness or drowsiness; avoid driving until you know how you react. · Report signs of depression (mood changes, insomnia) or slow heartbeat. · Avoid alcohol, which can increase dizziness and drowsiness. · This drug can make you more sensitive to sun; use sunscreen and protective clothing. · Do not take with MAO inhibitors; inform all healthcare providers you are taking this medication. · Monitor blood pressure regularly and keep appointments for lab tests (potassium, kidney function). |