HYDRO-SERP "50"
Clinical safety rating: caution
Comprehensive clinical and safety monograph for HYDRO-SERP "50" (HYDRO-SERP "50").
Hydrochlorothiazide inhibits the Na+-Cl- symporter in the distal convoluted tubule, increasing excretion of sodium, chloride, and water. Reserpine depletes catecholamines (norepinephrine, dopamine) from peripheral sympathetic nerve endings, reducing vascular tone and heart rate.
| Metabolism | Hydrochlorothiazide is not extensively metabolized. Reserpine is metabolized primarily in the liver by CYP450 enzymes. |
| Excretion | Renal (50-70% as unchanged drug and metabolites), biliary/fecal (20-30%) |
| Half-life | 50-100 hours (prolonged in renal impairment; half-life up to 200 hours in severe renal disease) |
| Protein binding | 90-96% (primarily to albumin and alpha1-acid glycoprotein) |
| Volume of Distribution | 200-400 L/kg (extremely large due to extensive tissue binding, especially in adrenergic nerve terminals) |
| Bioavailability | Oral: 40-50% (extensive first-pass metabolism) |
| Onset of Action | Oral: 3-6 days for full antihypertensive effect (delayed due to gradual depletion of catecholamines); IV: 2-4 hours |
| Duration of Action | Oral: 1-6 weeks (persistent effect after discontinuation due to long half-life and nerve terminal depletion); IV: 6-24 hours |
Hydrochlorothiazide 50 mg orally once daily.
| Dosage form | TABLET |
| Renal impairment | Contraindicated in anuria. For GFR 30-60 mL/min: reduce dose to 25 mg daily. For GFR <30 mL/min: not recommended. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B/C: use with caution; monitor electrolytes and renal function; reduce dose if needed. |
| Pediatric use | Not typically recommended; safety and efficacy not established. |
| Geriatric use | Initiate at 12.5-25 mg orally once daily; titrate cautiously; monitor electrolytes and renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for HYDRO-SERP "50" (HYDRO-SERP "50").
| Breastfeeding | Hydrochlorothiazide: Excreted into human milk in small amounts; M/P ratio approximately 0.2. Reserpine: Excreted into breast milk; M/P ratio not well established. Both are considered compatible with breastfeeding by most authorities, but use caution as reserpine may cause gastrointestinal disturbances, nasal congestion, and lethargy in the infant. Monitor infant for side effects. |
| Teratogenic Risk | Hydrochlorothiazide: First trimester: Crosses placenta, risk of fetal or neonatal jaundice, thrombocytopenia, and possibly other adverse effects; limited human data, association with congenital anomalies not established. Second and third trimesters: May cause fetal or neonatal electrolyte disturbances, hypoglycemia, and decreased placental perfusion. Reserpine: First trimester: Animal studies show no teratogenic effects, human data insufficient. Second and third trimesters: May cause neonatal respiratory depression, bradycardia, hypothermia, and nasal congestion due to depletion of catecholamines. |
■ FDA Black Box Warning
None
| Serious Effects |
["Anuria","Known sulfonamide allergy (hydrochlorothiazide)","History of mental depression (reserpine)","Active peptic ulcer or ulcerative colitis (reserpine)","Electroconvulsive therapy (reserpine)"]
| Precautions | ["Electrolyte imbalance (especially hypokalemia)","Sulfonamide allergy (hydrochlorothiazide)","Mental depression (reserpine)","Bradycardia and arrhythmias (reserpine)"] |
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| Fetal Monitoring | Monitor maternal blood pressure, serum electrolytes (sodium, potassium), renal function, and uric acid. Assess for signs of fetal distress and growth restriction via ultrasound. In neonates, monitor for electrolyte imbalance, hypoglycemia, jaundice, and thrombocytopenia. |
| Fertility Effects | Hydrochlorothiazide: No known direct effect on fertility. Reserpine: May interfere with reproductive function due to central nervous system effects and possible hormonal disturbances; animal studies suggest impaired fertility at high doses. Human data are limited. |