CHLOROTHIAZIDE-RESERPINE
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Chlorothiazide inhibits the sodium-chloride symporter (NCC) in the distal convoluted tubule of the nephron, reducing sodium and chloride reabsorption, leading to increased diuresis and natriuresis. Reserpine depletes catecholamines (norepinephrine, dopamine, serotonin) from peripheral sympathetic nerve endings by binding to and inhibiting the vesicular monoamine transporter (VMAT), resulting in reduced sympathetic outflow and vasodilation.
| Metabolism | Chlorothiazide is primarily excreted unchanged in urine; minimal hepatic metabolism. Reserpine is extensively metabolized via first-pass metabolism in the liver to various metabolites, including methyl reserpate and reserpic acid. |
| Excretion | Chlorothiazide: Renal excretion of unchanged drug (~90%) via tubular secretion; Reserpine: Hepatic metabolism with renal excretion of metabolites (30%) and fecal elimination (~60%). |
| Half-life | Chlorothiazide: Terminal half-life ~1.5-2 hours (prolonged in renal impairment); Reserpine: Biphasic with initial half-life ~4.5 hours and terminal half-life 50-100 hours. |
| Protein binding | Chlorothiazide: ~95% bound to plasma proteins; Reserpine: ~96% bound to albumin. |
| Volume of Distribution | Chlorothiazide: ~0.2 L/kg (limited to extracellular fluid); Reserpine: ~8-9 L/kg (extensive tissue distribution with high lipophilicity). |
| Bioavailability | Chlorothiazide: Oral bioavailability ~30-50% (incomplete absorption); Reserpine: Oral bioavailability ~30-50% due to extensive first-pass metabolism. |
| Onset of Action | Chlorothiazide: Oral diuresis within 2 hours; Reserpine: Oral antihypertensive effect onset 3-6 days. |
| Duration of Action | Chlorothiazide: Diuresis lasts 6-12 hours; Reserpine: Antihypertensive effect persists for 1-3 weeks after cessation due to irreversible monoamine depletion. |
| Molecular Weight | Chlorothiazide: 295.72 Da; Reserpine: 608.68 Da |
Oral: 500 mg chlorothiazide and 0.125 mg reserpine once daily; may increase to twice daily if needed. Maximum dose: 1 g chlorothiazide and 0.25 mg reserpine per day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: reduce dose by 50% or use alternative. GFR <30 mL/min: avoid use; chlorothiazide is ineffective. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce reserpine dose by 50% or use alternative. Child-Pugh C: avoid use due to risk of hepatic encephalopathy. |
| Pediatric use | Chlorothiazide: 10-20 mg/kg/day orally divided every 12 hours; reserpine: 0.01-0.02 mg/kg/day orally divided every 12 hours. Maximum chlorothiazide: 375 mg/day for children up to 2 years, 1 g/day for 2-12 years; reserpine: 0.25 mg/day. |
| Geriatric use | Start with lowest dose (250 mg chlorothiazide/0.125 mg reserpine) once daily; titrate cautiously due to increased risk of hypotension, electrolyte imbalance, and CNS effects. Monitor renal function and electrolytes frequently. |
| 1st trimester | Chlorothiazide is contraindicated in first trimester due to risk of fetal hypotension and electrolyte disturbances; reserpine is associated with increased risk of congenital malformations including neural tube defects. |
| 2nd trimester | Use only if clearly needed; may cause fetal jaundice, electrolyte abnormalities, and thrombocytopenia. Reserpine may cause fetal bradycardia and nasal congestion. |
| 3rd trimester | Avoid near term due to risk of neonatal thrombocytopenia, electrolyte imbalance, and hypotension. Reserpine may cause neonatal respiratory depression and nasal congestion. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Placental transfer | Both chlorothiazide and reserpine cross the placenta. Chlorothiazide achieves fetal serum concentrations similar to maternal; reserpine is detectable in fetal tissues. |
■ FDA Black Box Warning
None
| Common Effects | Depression |
| Serious Effects |
Hypersensitivity to chlorothiazide, reserpine, or sulfonamide derivativesAnuriaRenal failureHepatic comaHistory of mental depression (especially with suicidal tendency)Active peptic ulcerUlcerative colitisElectroconvulsive therapy
| Precautions | Electrolyte disturbances (hypokalemia, hyponatremia, hypomagnesemia), hyperuricemia, hyperglycemia, hypotension, sensitivity reactions (systemic lupus erythematosus exacerbation), increased risk of gout, photosensitivity, caution in hepatic impairment, renal impairment, pre-existing diabetes, history of major depression (especially with reserpine), history of peptic ulcer disease (reserpine increases gastric acid secretion), potential for drug interactions (e.g., digitalis, antihypertensives, corticosteroids). |
| Food/Dietary |
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| Breastfeeding | Chlorothiazide and reserpine are excreted into breast milk. Chlorothiazide may suppress lactation or cause electrolyte disturbances in the infant. Reserpine may cause drowsiness, diarrhea, and nasal congestion in the nursing infant. Use only if clearly needed and monitor infant for adverse effects. |
| Lactation Rating | L4 - Possibly Hazardous |
| Teratogenic Risk | Chlorothiazide-Reserpine: First trimester: Not recommended; thiazides have uncertain teratogenicity (possible fetal/neonatal electrolyte disturbances). Second/third trimesters: Avoid; may cause fetal/neonatal jaundice, thrombocytopenia, electrolyte abnormalities. Reserpine: crosses placenta; risk of neonatal respiratory depression, bradycardia, hypothermia. FDA Category C (reserpine) and D (chlorothiazide) if used in pregnancy-induced hypertension. |
| Fetal Monitoring | Maternal: Blood pressure, serum electrolytes (especially potassium), renal function, fetal ultrasound for growth restriction, nonstress test, biophysical profile. Neonatal: Monitor for jaundice, thrombocytopenia, electrolyte imbalances, respiratory depression. |
| Fertility Effects | Reserpine may cause menstrual irregularities, decreased libido, and galactorrhea. Chlorothiazide has no known direct effect on fertility. Overall, limited data; use with caution in women of childbearing potential. |
| Avoid excessive dietary sodium intake as it may counteract antihypertensive effect. Avoid natural licorice (glycyrrhizin) as it may cause hypokalemia and sodium retention. Limit alcohol consumption as it may enhance hypotensive effects and dizziness. Grapefruit juice may increase reserpine absorption; avoid concurrent consumption. |
| Clinical Pearls | Chlorothiazide-reserpine is a fixed-dose combination used for hypertension. Reserpine depletes catecholamines, causing delayed onset (weeks) and prolonged effect (weeks after discontinuation). Monitor for orthostatic hypotension, especially with concurrent diuretic therapy. Avoid in patients with history of depression or peptic ulcer disease due to reserpine's CNS and gastric effects. Hypokalemia from chlorothiazide may potentiate arrhythmias, especially with digoxin. Check electrolytes and renal function periodically. |
| Patient Advice | Take exactly as prescribed; do not stop suddenly as blood pressure may rise. · May cause dizziness or lightheadedness upon standing; rise slowly from sitting or lying positions. · Avoid alcohol and hot baths/showers as they can worsen dizziness. · Report any mood changes, depression, or suicidal thoughts to your doctor immediately. · This drug may cause nasal congestion; do not use over-the-counter decongestants without consulting your doctor. · Stay hydrated but avoid excessive salt intake; limit foods high in potassium unless advised by your doctor. · May cause increased urination; take in the morning to avoid nighttime trips to the bathroom. · Use sun protection; this drug may increase sensitivity to sunlight. |