HYDROCHLOROTHIAZIDE W/ RESERPINE AND HYDRALAZINE
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Hydrochlorothiazide inhibits the Na+/Cl- symporter in the distal convoluted tubule, reducing sodium and water reabsorption; reserpine depletes catecholamines from peripheral sympathetic nerve endings, reducing vascular tone and heart rate; hydralazine directly relaxes arteriolar smooth muscle, decreasing peripheral vascular resistance.
| Metabolism | Hydrochlorothiazide is not extensively metabolized; reserpine is hepatically metabolized via CYP3A4; hydralazine undergoes N-acetylation by NAT2 (polymorphic). |
| Excretion | Hydrochlorothiazide: 95% renal (unchanged and glucuronide conjugate). Reserpine: 30% renal (unchanged), 60% fecal (metabolites). Hydralazine: 60-65% renal (acetylated metabolites), 5-10% unchanged; 10% fecal. |
| Half-life | Hydrochlorothiazide: 6-15 hours (10 hours typical). Reserpine: 4.5-87 hours (biphasic, terminal 33 hours). Hydralazine: 2-8 hours (fast acetylators 2-4 hours, slow 4-8 hours). |
| Protein binding | Hydrochlorothiazide: 40-68% (albumin). Reserpine: 96% (albumin and beta-globulins). Hydralazine: 87-90% (albumin). |
| Volume of Distribution | Hydrochlorothiazide: 0.83-1.2 L/kg. Reserpine: 3.8-6.5 L/kg (extensive tissue binding). Hydralazine: 1.5-2.5 L/kg. |
| Bioavailability | Hydrochlorothiazide: 65-75% oral. Reserpine: 40-50% oral (extensive first-pass). Hydralazine: 30-50% oral (lean body mass; first-pass acetylation). |
| Onset of Action | Hydrochlorothiazide: diuresis within 2 hours. Reserpine: 3-6 days for antihypertensive effect. Hydralazine: 20-30 minutes oral; up to 1 hour for full effect. |
| Duration of Action | Hydrochlorothiazide: 6-12 hours. Reserpine: 2-6 weeks after discontinuation. Hydralazine: 3-8 hours (acetylator dependent). |
| Molecular Weight | Hydrochlorothiazide: 297.74 Da; Reserpine: 608.68 Da; Hydralazine: 160.17 Da |
1 tablet (hydrochlorothiazide 25 mg/reserpine 0.125 mg/hydralazine 25 mg) orally once daily. May increase to 2 tablets daily if needed.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR < 30 mL/min. For GFR 30-50 mL/min: use with caution, monitor electrolytes; avoid loop diuretic combination. For GFR > 50 mL/min: no adjustment needed. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: use with caution; consider reducing dose by 50% due to increased reserpine and hydralazine exposure. Child-Pugh C: avoid use. |
| Pediatric use | Not recommended for pediatric use due to lack of safety and efficacy data. |
| Geriatric use | Start at lowest dose (e.g., half tablet daily). Monitor for orthostatic hypotension, electrolyte disturbances, and CNS effects (reserpine). Avoid in patients with depression or severe renal impairment. |
| 1st trimester | Avoid; associated with fetal abnormalities including neural tube defects, cardiovascular malformations, and cleft lip/palate due to reserpine and hydralazine components. |
| 2nd trimester | Avoid; may cause fetal hypotension, renal impairment, electrolyte disturbances, and possible growth restriction. |
| 3rd trimester | Avoid; risk of neonatal complications such as hypotension, hypokalemia, thrombocytopenia, and respiratory depression. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Placental transfer | All three components cross the placenta; hydralazine and reserpine achieve significant fetal concentrations. Hydrochlorothiazide crosses readily and may cause fetal electrolyte disturbances. |
■ FDA Black Box Warning
Reserpine component: May cause mental depression, especially in patients with a history of depression; discontinue at first sign of depression.
| Common Effects | Depression |
| Serious Effects |
Known hypersensitivity to thiazides, reserpine, or hydralazineHistory of depression (especially with suicidal ideation) or electroconvulsive therapy (reserpine)Active peptic ulcer disease or ulcerative colitis (reserpine)Severe renal impairment (anuria, CrCl <30 mL/min)Severe hepatic impairmentCoronary artery disease or mitral valve rheumatic heart disease (hydralazine may exacerbate angina)Systemic lupus erythematosus (hydralazine may induce lupus)Concomitant MAO inhibitor therapyPheochromocytoma
| Precautions | Electrolyte imbalances (hypokalemia, hyponatremia), hypotension, lupus-like syndrome (hydralazine), depression (reserpine), increased risk of gout, sulfonamide allergy (hydrochlorothiazide cross-reactivity). |
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| Breastfeeding |
| Hydrochlorothiazide and reserpine are excreted into breast milk in small amounts; hydralazine is present in milk. The combination may suppress lactation, cause adverse effects in the infant (hypotension, electrolyte disturbances, extrapyramidal symptoms), and potential for kernicterus in jaundiced neonates. Not recommended during breastfeeding. |
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | First trimester: Reserpine crosses placenta, associated with increased risk of congenital malformations, including neural tube defects and cardiovascular anomalies. Hydralazine has been associated with fetal harm in animal studies; human data limited. Hydrochlorothiazide use in first trimester may increase risk of neural tube defects and oral clefts based on some studies. Second and third trimesters: Hydrochlorothiazide can cause fetal or neonatal jaundice, thrombocytopenia, and electrolyte disturbances. Reserpine may cause neonatal respiratory depression, bradycardia, and hypothermia. Hydralazine may cause fetal distress, hypotension, and reflex tachycardia. Combination product should be avoided during pregnancy. |
| Fetal Monitoring | Monitor maternal blood pressure, heart rate, and electrolytes (especially potassium, sodium, and bicarbonate). Assess for signs of fluid overload or dehydration. Fetal monitoring: ultrasound for growth restriction and amniotic fluid volume; nonstress test or biophysical profile if preeclampsia or fetal compromise suspected. Neonatal monitoring: observe for jaundice, thrombocytopenia, electrolyte imbalances, and bradycardia/hypotension after delivery. |
| Fertility Effects | Reserpine may cause hyperprolactinemia and inhibit ovulation through disruption of hypothalamic-pituitary axis. Hydralazine has been associated with reversible decreased libido and erectile dysfunction in males; no direct evidence of impaired fertility in females. Hydrochlorothiazide has no known significant effects on fertility. Use may adversely affect fertility, especially with reserpine component. |
| Food/Dietary |
| Avoid high-sodium foods, as they can decrease antihypertensive effect. Limit alcohol intake. Grapefruit juice may increase hydralazine levels; avoid excessive intake. Maintain adequate potassium intake (e.g., bananas, oranges) to counteract hypokalemia from thiazide. |
| Clinical Pearls | Monitor for orthostatic hypotension, especially at initiation. Reserpine may cause nasal congestion, depression, and increased gastric acid secretion; avoid in patients with peptic ulcer disease or history of depression. Hydralazine can induce a lupus-like syndrome, especially in slow acetylators. Thiazide diuretics may cause hypokalemia, hyperuricemia, and hyperglycemia. Combination product limits dose titration flexibility. |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. · Rise slowly from sitting or lying down to prevent dizziness. · Avoid alcohol, which can worsen low blood pressure. · Report unusual tiredness, depression, joint pain, fever, or chest pain to your doctor. · Use sunscreen and protective clothing; this medication may increase sun sensitivity. |