RESERPINE, HYDROCHLOROTHIAZIDE, AND HYDRALAZINE HYDROCHLORIDE
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Reserpine irreversibly inhibits the vesicular monoamine transporter (VMAT), depleting catecholamines and serotonin in peripheral sympathetic neurons. Hydrochlorothiazide inhibits the Na+/Cl- cotransporter in the distal convoluted tubule, reducing sodium and water reabsorption. Hydralazine directly vasodilates arterioles by relaxing vascular smooth muscle, possibly via nitric oxide-mediated guanylate cyclase activation.
| Metabolism | Reserpine: extensively metabolized in the liver via CYP enzymes (unknown specific isoenzymes). Hydrochlorothiazide: not metabolized; eliminated unchanged renally. Hydralazine: metabolized by hepatic N-acetyltransferase (NAT2); acetylation polymorphism. |
| Excretion | Reserpine: renal (60-70% as metabolites, <1% unchanged) and fecal (10-30%). Hydrochlorothiazide: renal (≥95% unchanged via tubular secretion). Hydralazine: renal (80-90% as metabolites, including acetylation products, and 10-15% unchanged). |
| Half-life | Reserpine: 50-100 hours (long, allows once-daily dosing; cumulative effects may persist after discontinuation). Hydrochlorothiazide: 6-15 hours (prolonged in renal impairment). Hydralazine: fast acetylators 2-4 hours, slow acetylators 4-8 hours (variable; justifies twice-daily dosing). |
| Protein binding | Reserpine: 95-96% (mainly albumin). Hydrochlorothiazide: 40-68% (albumin). Hydralazine: 85-90% (albumin and α1-acid glycoprotein). |
| Volume of Distribution | Reserpine: 1.6-3.4 L/kg (extensive tissue binding). Hydrochlorothiazide: 0.83-1.4 L/kg (not extensively distributed). Hydralazine: 0.5-0.8 L/kg (slow acetylators have lower Vd due to slower clearance). |
| Bioavailability | Reserpine: oral 50-60% (extensive first-pass metabolism). Hydrochlorothiazide: oral 65-75% (absorption reduced by food). Hydralazine: oral 30-50% (fast acetylators lower due to high first-pass acetylation; slow acetylators 30-50%). |
| Onset of Action | Oral: Reserpine 3-6 days (antihypertensive effect), Hydrochlorothiazide 2 hours (diuresis), Hydralazine 30-60 minutes (vasodilation). |
| Duration of Action | Reserpine: 6-24 hours (antihypertensive effect may persist up to weeks after cessation). Hydrochlorothiazide: 6-12 hours (diuresis). Hydralazine: 6-12 hours (antihypertensive effect; duration may be shorter in fast acetylators). |
| Molecular Weight | Reserpine: 608.68 Da (as reserpine base). Hydrochlorothiazide: 297.74 Da. Hydralazine hydrochloride: 196.64 Da (free base 160.18 Da). |
Each tablet contains reserpine 0.1 mg, hydrochlorothiazide 25 mg, and hydralazine hydrochloride 25 mg. One tablet orally once or twice daily, not to exceed 2 tablets per day.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in anuria or severe renal impairment (CrCl <30 mL/min). For CrCl 30-60 mL/min, reduce dose by 50% (maximum 1 tablet daily). Monitor electrolytes and renal function. |
| Liver impairment | Contraindicated in severe hepatic impairment (Child-Pugh class C). For Child-Pugh class B, reduce dose by 50% and monitor for signs of hepatic encephalopathy. For Child-Pugh class A, no adjustment needed but caution advised. |
| Pediatric use | Not recommended for pediatric use due to lack of safety and efficacy data. |
| Geriatric use | Initiate at half the standard dose (0.5 tablet daily) due to increased sensitivity, risk of hypotension, electrolyte imbalance, and impaired renal function. Monitor blood pressure and electrolytes closely. |
| 1st trimester | Reserpine: Crosses placenta; associated with increased risk of congenital malformations, including neural tube defects. Hydrochlorothiazide: May cause fetal electrolyte disturbances, jaundice, thrombocytopenia. Hydralazine: Inadequate human data; animal studies show adverse effects. Avoid in first trimester unless benefit outweighs risk. |
| 2nd trimester | Reserpine: Continued risk of fetal harm; may cause neonatal respiratory depression, bradycardia, and hypothermia. Hydrochlorothiazide: Risk of electrolyte imbalance, potential for decreased placental perfusion. Hydralazine: Use with caution; monitor maternal blood pressure and fetal status. Generally avoided if safer alternatives exist. |
| 3rd trimester | Reserpine: Risk of neonatal adverse effects (nasal congestion, lethargy, poor feeding) due to reserpine. Hydrochlorothiazide: May cause fetal or neonatal jaundice, thrombocytopenia, and electrolyte disturbances. Hydralazine: Risk of maternal hypotension and fetal distress. Avoid use near term. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
■ FDA Black Box Warning
None.
| Common Effects | Depression |
| Serious Effects |
Hypersensitivity to any componentActive peptic ulcer disease (reserpine)Ulcerative colitis (reserpine)History of mental depression, especially with suicidal tendencies (reserpine)Electroconvulsive therapy (reserpine)Anuria (hydrochlorothiazide)Severe renal impairment (hydrochlorothiazide)Coronary artery disease or mitral valve rheumatic heart disease (hydralazine)Aortic aneurysm (hydralazine)
| Precautions | Reserpine: risk of depression, peptic ulcer, and extrapyramidal symptoms; avoid in patients with a history of depression. Hydrochlorothiazide: electrolyte disturbances (hypokalemia, hyponatremia), hyperuricemia, hyperglycemia; may exacerbate renal insufficiency. Hydralazine: drug-induced lupus-like syndrome, peripheral neuritis (pyridoxine deficiency), tachycardia, and angina; use with caution in coronary artery disease. |
| Food/Dietary |
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| Placental transfer | Reserpine: Readily crosses placenta. Hydrochlorothiazide: Crosses placenta. Hydralazine: Crosses placenta (fetal plasma levels 50-100% of maternal). All three transfer. |
| Breastfeeding | Reserpine is excreted into breast milk and may cause adverse effects in the nursing infant (nasal congestion, diarrhea, sedation). Hydrochlorothiazide is excreted in small amounts; may suppress lactation. Hydralazine is excreted in small amounts; no reported adverse effects. Caution is advised; consider an alternative antihypertensive. |
| Lactation Rating | L4 (possibly hazardous) for reserpine component; overall combination rating L4 due to reserpine risks. |
| Teratogenic Risk | First trimester: Reserpine crosses placenta; limited human data but animal studies show no teratogenicity; may cause respiratory depression, bradycardia, hypothermia in neonate. Hydrochlorothiazide: not associated with major malformations but may cause electrolyte disturbances, thrombocytopenia, jaundice. Hydralazine: no evidence of teratogenicity in humans. Second and third trimesters: Reserpine may cause neonatal respiratory depression, bradycardia; hydrochlorothiazide may cause fetal/neonatal jaundice, thrombocytopenia, electrolyte imbalance; hydralazine may cause neonatal thrombocytopenia, lupus-like syndrome. Overall, use only if benefit outweighs risk; avoid in preeclampsia due to potential maternal hypotension. |
| Fetal Monitoring | Maternal: Blood pressure, heart rate, serum electrolytes (potassium, sodium), renal function, complete blood count, signs of lupus-like syndrome (hydralazine), depression (reserpine). Fetal: Ultrasound for growth and amniotic fluid volume (hydrochlorothiazide may cause oligohydramnios), fetal heart rate monitoring in third trimester. |
| Fertility Effects | Reserpine: may cause menstrual irregularities, galactorrhea, decreased libido in females; gynecomastia in males. Hydrochlorothiazide: no known direct effect on fertility. Hydralazine: no known direct effect on fertility. Limited data on combination drug. Potential reversible impact on spermatogenesis (reserpine). |
| Avoid grapefruit juice as it may affect hydralazine metabolism. Limit sodium intake to control blood pressure. Maintain consistent intake of potassium-rich foods (bananas, oranges, spinach) but avoid excessive supplementation unless prescribed. Avoid alcohol due to additive hypotensive effects. |
| Clinical Pearls | Reserpine depletes catecholamines; may cause severe depression. Hydrochlorothiazide is a thiazide diuretic; monitor electrolytes, especially potassium and magnesium. Hydralazine is a vasodilator; can cause drug-induced lupus (ANA testing recommended). Combination lowers BP via multiple mechanisms; watch for orthostatic hypotension, especially in elderly. Avoid abrupt discontinuation of reserpine to prevent sympathetic surge. Use with caution in patients with history of peptic ulcer (reserpine increases gastric acid secretion). |
| Patient Advice | Take this medication exactly as prescribed, usually once daily. · Avoid sudden stopping of the medication; consult your doctor before discontinuing. · Stand up slowly from sitting or lying positions to prevent dizziness. · Monitor for signs of depression, such as persistent sadness, loss of interest, or sleep disturbances. · Report any new or worsening muscle pain, fever, or rash (possible lupus). · Limit alcohol intake as it may worsen low blood pressure. · Use sun protection as hydrochlorothiazide increases skin sensitivity to sunlight. · Avoid potassium supplements or salt substitutes containing potassium unless directed by your doctor. · Maintain adequate fluid intake; avoid dehydration from diarrhea or vomiting. |