RESERPINE AND HYDROCHLOROTHIAZIDE
Clinical safety rating: safe
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
Reserpine is an adrenergic neuron blocking agent that depletes catecholamines and serotonin from central and peripheral neurons by inhibiting the vesicular monoamine transporter (VMAT). Hydrochlorothiazide is a thiazide diuretic that inhibits the sodium-chloride symporter in the distal convoluted tubule, reducing electrolyte resorption and causing diuresis.
| Metabolism | Reserpine is metabolized primarily by CYP3A4; Hydrochlorothiazide is not extensively metabolized (mostly excreted unchanged in urine). |
| Excretion | Reserpine: primarily renal (30-60% as metabolites, <1% unchanged) and fecal (40-60% via bile). Hydrochlorothiazide: predominantly renal (≥95% unchanged via glomerular filtration and tubular secretion). |
| Half-life | Reserpine: terminal half-life 50-100 hours (up to 11 days with chronic dosing due to tissue binding); clinically, antihypertensive effect persists for 1-6 weeks after discontinuation. Hydrochlorothiazide: terminal half-life 6-15 hours (mean ~9 hours); in renal impairment, half-life prolonged up to 24-40 hours. |
| Protein binding | Reserpine: approximately 96% bound to plasma proteins (primarily albumin). Hydrochlorothiazide: 65-70% bound to plasma proteins (mainly albumin). |
| Volume of Distribution | Reserpine: Vd 9.1 L/kg; extensive tissue distribution with high affinity for adipose tissue and brain. Hydrochlorothiazide: Vd 0.2-0.83 L/kg (mean ~0.55 L/kg); limited to extracellular fluid. |
| Bioavailability | Reserpine: oral bioavailability ~50% (extensive first-pass metabolism). Hydrochlorothiazide: oral bioavailability ~65-75% (range 50-80% due to saturable absorption). |
| Onset of Action | Reserpine: oral antihypertensive effect in 3-6 days; maximal effect in 3-6 weeks. Hydrochlorothiazide: oral diuresis begins within 2 hours, peak at 4-6 hours; antihypertensive effect in 2-3 days, maximal in 3-4 weeks. |
| Duration of Action | Reserpine: antihypertensive effect persists for 1-6 weeks after discontinuation due to irreversible binding. Hydrochlorothiazide: diuretic effect lasts ~6-12 hours; antihypertensive effect sustained for 24 hours with daily dosing. |
| Molecular Weight | Reserpine: 608.68 Da; Hydrochlorothiazide: 297.74 Da |
One tablet (0.125 mg reserpine and 25 mg hydrochlorothiazide) orally once daily. May be increased to two tablets once daily if needed. Maximum dose: 2 tablets (0.25 mg reserpine and 50 mg hydrochlorothiazide) per day.
| Dosage form | TABLET |
| Renal impairment | Contraindicated if GFR <30 mL/min. For GFR 30-60 mL/min: use with caution, monitor electrolytes, start at lowest dose. No dose adjustment specified for GFR >60 mL/min. |
| Liver impairment | Contraindicated in Child-Pugh class B or C. For Child-Pugh class A: use with caution, start at lowest dose, monitor for hepatic encephalopathy. No specific dose reduction quantified. |
| Pediatric use | Not recommended for use in pediatric patients due to lack of safety and efficacy data. |
| Geriatric use | Initiate at low end of dosing range (0.125 mg reserpine/25 mg hydrochlorothiazide once daily). Monitor for orthostatic hypotension, electrolyte imbalance, and renal function. Avoid if possible due to increased risk of adverse effects. |
| 1st trimester | Reserpine crosses the placenta and is associated with increased risk of congenital malformations (neural tube defects, cardiovascular) based on animal and limited human data. Hydrochlorothiazide is generally avoided in first trimester due to potential teratogenic effects (cleft lip/palate) in animal studies. Use contraindicated. |
| 2nd trimester | Reserpine is contraindicated due to risk of fetal bradycardia, hypothermia, and respiratory depression. Hydrochlorothiazide may cause fetal electrolyte disturbances and is generally avoided. Combined use not recommended. |
| 3rd trimester | Reserpine can cause neonatal bradycardia, respiratory depression, and hypothermia. Hydrochlorothiazide may cause neonatal jaundice, thrombocytopenia, and electrolyte imbalance. Avoid use near term. |
Clinical note
MAOIs can cause excitability and hypertension Can cause depression and suicidal ideation.
| FDA category | Animal |
| Placental transfer |
■ FDA Black Box Warning
None
| Common Effects | Depression |
| Serious Effects |
Active peptic ulcerUlcerative colitisKnown hypersensitivity to reserpine, hydrochlorothiazide, or sulfonamide-derived drugsElectroshock therapy (within 7 days)Severe renal impairment (CrCl <30 mL/min)Severe hepatic impairmentPregnancy (especially first trimester)BreastfeedingAnuriaConcurrent MAO inhibitor therapy
| Precautions | Risk of depression, especially in patients with history; discontinue if signs appear., May precipitate peptic ulcer disease; use cautiously in patients with history., Electrolyte imbalances, including hypokalemia, hyponatremia, and hypomagnesemia., Hyperuricemia may occur; monitor serum uric acid levels., May cause drowsiness or dizziness; caution with driving/operating machinery. |
| Food/Dietary |
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| Both reserpine and hydrochlorothiazide cross the human placenta. Reserpine has been detected in fetal tissues, and fetal exposure is significant. |
| Breastfeeding | Reserpine is excreted into breast milk and may cause adverse effects in nursing infants (e.g., bradycardia, hypotension, nasal congestion). Hydrochlorothiazide is also excreted in breast milk and may suppress lactation or cause electrolyte disturbances. Avoid breastfeeding during therapy due to both components. |
| Lactation Rating | L5 (Contraindicated) |
| Teratogenic Risk | First trimester: Reserpine crosses placenta; risk of fetal bradycardia, hypotonia, and hypothermia. Second/third trimester: Hydrochlorothiazide may cause fetal/neonatal electrolyte disturbances, jaundice, and thrombocytopenia. Use only if benefit outweighs risk. |
| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (especially potassium, bicarbonate), renal function, and uric acid. Fetal monitoring for growth restriction, arrhythmias, and electrolyte imbalance via ultrasound and fetal heart rate. |
| Fertility Effects | Hydrochlorothiazide may cause gynecomastia and erectile dysfunction in males; reserpine may impair libido and induce galactorrhea. Both may reduce fertility potential transiently. |
| Avoid high-sodium foods as they can counteract antihypertensive effect. Limit alcohol intake. Avoid excessive potassium intake or potassium supplements unless directed by physician, as hydrochlorothiazide can cause hypokalemia but reserpine may mask toxicity. Grapefruit juice may alter drug metabolism; avoid large amounts. Tyramine-rich foods (aged cheese, cured meats, fermented products) may rarely cause hypertensive crisis due to reserpine's catecholamine depletion. |
| Clinical Pearls | Reserpine depletes catecholamines and serotonin from postganglionic adrenergic nerve endings, causing gradual onset of antihypertensive effect over 2–3 weeks. Hydrochlorothiazide is a thiazide diuretic that initially reduces plasma volume and later decreases peripheral resistance. Monitor for depression, nasal congestion, bradycardia, and electrolyte imbalances (especially hypokalemia and hyponatremia). Avoid in patients with history of depression, peptic ulcer disease, or pheochromocytoma. Reserpine can cause extrapyramidal symptoms and pseudoparkinsonism. Hydrochlorothiazide may exacerbate gout and hypercalcemia. Use with caution in renal impairment (CrCl <30 mL/min). |
| Patient Advice | Take this medication exactly as prescribed; do not stop abruptly. · Avoid alcohol and other sedatives as reserpine can cause drowsiness. · Report signs of depression (mood changes, insomnia, loss of interest). · Rise slowly from sitting or lying to prevent dizziness from low blood pressure. · Maintain adequate fluid intake and avoid excessive salt substitutes high in potassium. · Monitor for swelling, weight gain, or shortness of breath, which may indicate fluid retention. · Avoid prolonged sun exposure and use sunscreen as hydrochlorothiazide increases photosensitivity. · Do not take other medications without consulting your doctor, especially cold remedies or appetite suppressants. · Regular blood tests may be needed to check electrolytes and kidney function. |