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. |
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 | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Breastfeeding | Chlorothiazide: Excreted in breast milk; M/P ratio unknown; may suppress lactation. Reserpine: Excreted in breast milk; M/P ratio unknown; may cause infant sedation, diarrhea, nasal congestion. Avoid breastfeeding or use alternative antihypertensive. |
| 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. |
■ FDA Black Box Warning
None
| Common Effects | Depression |
| Serious Effects |
Anuria, hypersensitivity to sulfonamides (for chlorothiazide) or to reserpine, severe renal impairment (creatinine clearance <30 mL/min), hepatic coma or pre-coma, active peptic ulcer disease, ulcerative colitis, electroconvulsive therapy, history of major depression (especially with high doses), concurrent MAO inhibitor therapy (due to reserpine).
| 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). |
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| 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. |