CHLOROTHIAZIDE W/ RESERPINE
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Chlorothiazide inhibits the Na+/Cl- cotransporter in the distal convoluted tubule, reducing sodium and water reabsorption. Reserpine depletes catecholamines from postganglionic sympathetic nerve endings by inhibiting the vesicular monoamine transporter (VMAT), leading to reduced peripheral vascular resistance and central nervous system depletion.
| Metabolism | Chlorothiazide: Not extensively metabolized; excreted unchanged in urine. Reserpine: Extensively metabolized in the liver via hydrolysis and conjugation; undergoes enterohepatic circulation. |
| Excretion | Chlorothiazide: primarily renal (90-95% unchanged via tubular secretion); Reserpine: hepatic metabolism, renal excretion of metabolites (60% as metabolites, <1% unchanged). |
| Half-life | Chlorothiazide: 1.5-2 hours; Reserpine: 50-100 hours (terminal, due to enterohepatic recirculation and tissue binding). |
| Protein binding | Chlorothiazide: 20-40% bound to albumin; Reserpine: >95% bound to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Chlorothiazide: 0.2-0.4 L/kg (confined to extracellular fluid); Reserpine: 8-10 L/kg (extensive tissue binding, particularly lipid-rich tissues). |
| Bioavailability | Chlorothiazide: oral 30-50% (luminal degradation and limited absorption); Reserpine: oral 50-60% (extensive first-pass hepatic metabolism). |
| Onset of Action | Chlorothiazide: oral diuresis within 2 hours; Reserpine: oral hypotensive effect within 3-6 hours. |
| Duration of Action | Chlorothiazide: diuresis lasts 6-12 hours; Reserpine: hypotensive effect persists 1-2 weeks after discontinuation due to irreversible vesicular monoamine depletion. |
| Molecular Weight | Chlorothiazide: 295.72 Da; Reserpine: 608.68 Da |
Oral, 500 mg chlorothiazide / 0.125 mg reserpine once or twice daily. Maximum daily dose: 1000 mg chlorothiazide / 0.25 mg reserpine.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: reduce dose by 50% or extend interval; GFR <30 mL/min: contraindicated. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: avoid use. |
| Pediatric use | Chlorothiazide: 10-20 mg/kg/day orally in 2 divided doses; reserpine: 0.005-0.02 mg/kg/day orally in 1-2 divided doses. Maximum pediatric dose: 375 mg chlorothiazide/0.05 mg reserpine per day. |
| Geriatric use | Initiate at lowest dose (250 mg chlorothiazide/0.1 mg reserpine daily). Monitor for orthostatic hypotension, electrolyte disturbances, and CNS depression. Adjust based on renal function. |
| 1st trimester | Avoid. Reserpine crosses placenta; may cause fetal bradycardia, respiratory depression, and hypothermia. Thiazide diuretics may reduce placental perfusion. |
| 2nd trimester | Avoid. Continued risk of fetal adverse effects from reserpine (nasal congestion, lethargy) and thiazide (electrolyte imbalances, oligohydramnios). |
| 3rd trimester | Avoid. Reserpine can cause neonatal respiratory depression, bradycardia, and hypothermia. Thiazides may cause fetal or neonatal jaundice, thrombocytopenia. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Placental transfer | Reserpine crosses the placenta readily; chlorothiazide crosses but to a lesser extent. |
| Breastfeeding |
■ FDA Black Box Warning
Reserpine component: May increase risk of breast cancer in postmenopausal women (based on epidemiological studies); also associated with mental depression, especially in patients with a history of depression.
| Common Effects | Depression |
| Serious Effects |
Hypersensitivity to chlorothiazide, reserpine, or sulfonamide derivativesHistory of mental depression (especially with suicidal tendencies)Active peptic ulcer diseaseUlcerative colitisElectroconvulsive therapy (within 7 days)Severe renal impairment (anuria) or severe hepatic impairment
| Precautions | Electrolyte imbalance (hypokalemia, hyponatremia) with chlorothiazide, Orthostatic hypotension and bradycardia with reserpine, Depression risk with reserpine; avoid in patients with history of depression, Sulfonamide sensitivity cross-reactivity (chlorothiazide is a sulfonamide derivative), May exacerbate systemic lupus erythematosus, Gout and hyperuricemia with chlorothiazide |
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| Reserpine is excreted into breast milk and may cause adverse effects in nursing infants, including nasal congestion, respiratory depression, and bradycardia. Chlorothiazide is also excreted but in low amounts; however, combination therapy is not recommended during breastfeeding due to reserpine risks. |
| Lactation Rating | L5 (Contraindicated per manufacturer; avoid breastfeeding) |
| Teratogenic Risk | First trimester: Limited data, but thiazide diuretics are generally avoided due to potential placental hypoperfusion. Second/third trimester: May cause electrolyte disturbances, fetal/neonatal jaundice, thrombocytopenia, and possible fetal/neonatal hypotension. Reserpine may increase risk of neonatal respiratory depression, nasal congestion, and lethargy. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium, sodium, chloride), renal function, and blood glucose. Fetal monitoring for growth, amniotic fluid volume, and signs of distress. Neonatal monitoring for electrolyte imbalance, jaundice, thrombocytopenia, and respiratory depression. |
| Fertility Effects | Chlorothiazide: No direct evidence of impaired fertility. Reserpine: May cause menstrual irregularities and decreased libido in females; in males, may reduce seminal volume and sperm motility. Potential impact on ovulation and spermatogenesis. |
| Food/Dietary |
| Avoid foods high in sodium as they may counteract antihypertensive effects. Limit alcohol intake. May increase potassium loss; ensure adequate potassium intake from foods like bananas, oranges, and potatoes unless contraindicated. Avoid natural licorice as it can worsen hypokalemia. |
| Clinical Pearls | Chlorothiazide is a thiazide diuretic; reserpine is a rauwolfia alkaloid that depletes catecholamines. Combination used historically for hypertension. Monitor for hypokalemia, hyperuricemia, and electrolyte imbalance. Reserpine may cause nasal congestion, depression, and bradycardia. Avoid use in patients with history of depression, peptic ulcer, or pheochromocytoma. Onset of antihypertensive effect is gradual over weeks. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. · You may experience dizziness or lightheadedness; rise slowly from sitting or lying down. · Avoid alcohol as it can increase side effects like dizziness. · Report symptoms of depression, mood changes, or unusual tiredness. · This drug may increase blood sugar; monitor if diabetic. · Avoid excessive sun exposure; use sunscreen as this drug can increase sun sensitivity. · Do not stop taking this medication abruptly; withdrawal may cause rapid blood pressure increase. · Regular blood tests may be needed to check electrolytes, uric acid, and kidney function. |