RESERPINE AND HYDROCHLOROTHIAZIDE-50
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Reserpine irreversibly inhibits the vesicular monoamine transporter 2 (VMAT2), depleting presynaptic stores of catecholamines (norepinephrine, dopamine, serotonin) in central and peripheral neurons, leading to reduced sympathetic outflow. Hydrochlorothiazide is a thiazide-type diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, increasing sodium, chloride, and water excretion, thereby reducing plasma volume and cardiac output.
| Metabolism | Reserpine is extensively metabolized via hepatic CYP450 enzymes (primarily CYP3A4) to inactive metabolites. Hydrochlorothiazide undergoes minimal hepatic metabolism; most is excreted unchanged in urine. |
| Excretion | Reserpine: renal (30% as metabolites, <1% unchanged); fecal (60% as metabolites). Hydrochlorothiazide: renal (≥95% unchanged via active tubular secretion). |
| Half-life | Reserpine: 50-100 hours (biphasic, terminal half-life 4.5-11 days due to enterohepatic recirculation). Hydrochlorothiazide: 6-15 hours (increased in renal impairment). |
| Protein binding | Reserpine: ~96% bound to plasma proteins (mainly albumin and alpha-1 acid glycoprotein). Hydrochlorothiazide: 68% bound to albumin. |
| Volume of Distribution | Reserpine: 7.5-8.5 L/kg (extensive tissue binding, especially adipose and brain). Hydrochlorothiazide: 3-5 L/kg (distributes into erythrocytes). |
| Bioavailability | Reserpine: oral 50% (variable due to first-pass metabolism). Hydrochlorothiazide: oral 65-75% (reduced with food). |
| Onset of Action | Reserpine: oral 3-6 hours (antihypertensive effect). Hydrochlorothiazide: oral 2 hours (diuresis). |
| Duration of Action | Reserpine: oral 6-24 hours (antihypertensive). Hydrochlorothiazide: oral 6-12 hours (diuresis). |
| Molecular Weight | Reserpine: 608.68 Da; Hydrochlorothiazide: 297.74 Da |
1 tablet (containing 0.1 mg reserpine and 50 mg hydrochlorothiazide) orally once daily; may increase to 2 tablets daily in divided doses if needed.
| Dosage form | TABLET |
| Renal impairment | Hydrochlorothiazide: Contraindicated if GFR <30 mL/min; for GFR 30–50 mL/min, use reduced dose (e.g., 25 mg hydrochlorothiazide component) or alternative. Reserpine: No specific adjustment, but use caution if severe impairment. |
| Liver impairment | Reserpine (Child-Pugh A or B): No specific adjustment; Child-Pugh C: Avoid due to risk of hepatic encephalopathy. Hydrochlorothiazide (Child-Pugh A or B): Use caution; Child-Pugh C: Avoid due to risk of electrolyte disturbances and hypokalemia precipitating encephalopathy. |
| Pediatric use | Not typically recommended; if used, reserpine dose: 0.02–0.25 mg/kg/day in 1–2 divided doses (max 5 mg/day); hydrochlorothiazide dose: 2–3 mg/kg/day in 2 divided doses (max 50 mg/day). Base on weight. |
| Geriatric use | Start with 0.5 tablet (0.05 mg reserpine/25 mg hydrochlorothiazide) once daily; monitor for orthostatic hypotension, electrolyte imbalance, and CNS depression. Adjust slowly. |
| 1st trimester | Reserpine crosses placenta; associated with increased risk of congenital malformations (neural tube defects, cleft palate) and neonatal effects (respiratory depression, bradycardia, hypothermia). Hydrochlorothiazide may cause fetal electrolyte disturbances and volume depletion. Avoid use in first trimester unless benefit outweighs risk. |
| 2nd trimester | Reserpine and hydrochlorothiazide continue to pose risks including fetal growth restriction, electrolyte imbalances, and potential teratogenicity. Use only if essential and monitor maternal and fetal status closely. |
| 3rd trimester | Reserpine can cause neonatal respiratory depression, bradycardia, and hypothermia. Hydrochlorothiazide may cause neonatal thrombocytopenia, electrolyte disturbances, and possibly fetal hypotension. Avoid during third trimester due to risk of adverse neonatal outcomes. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Placental transfer |
■ FDA Black Box Warning
None
| Common Effects | Depression |
| Serious Effects |
Hypersensitivity to reserpine, hydrochlorothiazide, or sulfonamide-derived drugsHistory of mental depression (especially with suicidal tendencies)Active peptic ulcer or ulcerative colitisElectroshock therapy (within 7 days)AnuriaSevere renal impairment (CrCl <30 mL/min)Hepatic coma or precomaPregnancy (especially third trimester)
| Precautions | May cause mental depression, especially at higher doses; discontinue if signs of depression appear., Electrolyte imbalances (hypokalemia, hyponatremia, hypomagnesemia, hypercalcemia) with hydrochlorothiazide; monitor electrolytes., Sulfonamide-related hypersensitivity reactions; cross-sensitivity with other sulfonamides possible., May precipitate gout or hyperuricemia; monitor uric acid., Use caution in patients with renal impairment; avoid in anuria., May increase lithium toxicity; monitor lithium levels., Reserpine may cause bradycardia, orthostatic hypotension, and nasal congestion. |
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| Reserpine crosses the placenta readily; hydrochlorothiazide crosses the placenta with measurable fetal serum levels. Both have been detected in cord blood and amniotic fluid. |
| Breastfeeding | Reserpine is excreted into breast milk; potentially causing respiratory depression, bradycardia, and hyperprolactinemia in the infant. Hydrochlorothiazide is excreted in low amounts but may suppress lactation. Use with caution; monitor infant for sedation, poor feeding, and electrolyte imbalances. Consider alternative antihypertensives. |
| Lactation Rating | L4 |
| Teratogenic Risk | First trimester: Reserpine crosses placenta; risk of congenital malformations not established but animal studies show fetal harm. Hydrochlorothiazide associated with neural tube defects in early pregnancy. Second trimester: Risk of fetal bradycardia with reserpine; diuretic use may reduce placental perfusion. Third trimester: Reserpine may cause neonatal respiratory depression, bradycardia, hypothermia, and nasal congestion. Hydrochlorothiazide can cause electrolyte disturbances in neonate. |
| Fetal Monitoring | Monitor maternal blood pressure closely, avoid hypotension. Check maternal serum electrolytes (sodium, potassium) regularly due to thiazide. Assess fetal growth via ultrasound for potential intrauterine growth restriction. Monitor fetal heart rate for bradycardia. In third trimester, assess neonatal for symptoms of reserpine withdrawal. |
| Fertility Effects | Reserpine may cause hyperprolactinemia, leading to decreased libido, menstrual irregularities, and impaired fertility. Hydrochlorothiazide has no known direct effect on fertility. |
| Food/Dietary | Avoid excessive intake of sodium (salt) as it can counteract the antihypertensive effect. Limit alcohol consumption. Hydrochlorothiazide may cause potassium loss; consume potassium-rich foods (e.g., bananas, oranges, potatoes) unless otherwise advised. Avoid high-tyramine foods (e.g., aged cheeses, cured meats, sauerkraut) as reserpine may theoretically potentiate pressor response, though risk is lower than with MAOIs. |
| Clinical Pearls | Reserpine depletes catecholamines and serotonin from postganglionic adrenergic nerve endings, leading to orthostatic hypotension, nasal congestion, and increased gastric acid secretion. Hydrochlorothiazide is a thiazide diuretic causing hypokalemia, hyponatremia, hyperuricemia, and hyperglycemia. Monitor electrolytes, renal function, and blood pressure regularly. Avoid use in patients with a history of depression, peptic ulcer disease, or gout. Combination may cause severe bradycardia and sedation. Discontinue reserpine 2 weeks before electroconvulsive therapy. Use with caution in patients on digoxin due to hypokalemia risk. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily in the morning with food to reduce stomach upset. · Rise slowly from sitting or lying down to prevent dizziness or fainting due to low blood pressure. · You may experience nasal congestion, drowsiness, or vivid dreams - especially early in treatment. · Avoid alcohol as it can worsen dizziness and drowsiness. · Report any signs of depression, unusual weight gain, or swelling of ankles or feet to your doctor. · This medication may increase your blood sugar and uric acid levels; monitor if you have diabetes or gout. · Do not stop taking this medication abruptly without consulting your doctor, as blood pressure may rise rapidly. · Wear sunscreen and protective clothing, as hydrochlorothiazide can increase sensitivity to sunlight. |