HYDRO-SERP "25"
Clinical safety rating
cautionComprehensive clinical and safety monograph for HYDRO-SERP "25" (HYDRO-SERP "25").
Hydrochlorothiazide inhibits the Na+/Cl- symporter in the distal convoluted tubule of the kidney, reducing sodium and chloride reabsorption and promoting diuresis. Reserpine depletes catecholamines in postganglionic sympathetic nerve endings by inhibiting the vesicular monoamine transporter, leading to reduced sympathetic outflow and vasodilation.
| Metabolism | Hydrochlorothiazide is not extensively metabolized; reserpine is extensively metabolized in the liver via CYP450 enzymes. |
| Excretion | Renal (approximately 30-50% as unchanged drug and metabolites), biliary/fecal (approximately 50-70% as metabolites, with enterohepatic recirculation noted for reserpine component). |
| Half-life | Reserpine: terminal elimination half-life 33-45 hours (range 30-60 hours), with clinical context of prolonged autonomic effects lasting days; hydrochlorothiazide: terminal half-life 6-15 hours (mean 10 hours). |
| Protein binding | Reserpine: 95-98% bound to plasma proteins; hydrochlorothiazide: 60-70% bound to albumin. |
| Volume of Distribution | Reserpine: Vd approximately 0.5-0.7 L/kg, indicating extensive tissue distribution and high lipophilicity; hydrochlorothiazide: Vd 0.2-0.4 L/kg, primarily confined to extracellular fluid. |
| Bioavailability | Reserpine: oral bioavailability approximately 50% due to first-pass metabolism; hydrochlorothiazide: oral bioavailability 65-75%. |
| Onset of Action | Reserpine: oral 3-7 days for full antihypertensive effect; hydrochlorothiazide: oral 2 hours (diuresis), 3-4 hours (peak antihypertensive). |
| Duration of Action | Reserpine: oral 1-2 weeks after discontinuation due to irreversible binding to monoamine transporters; hydrochlorothiazide: oral 6-12 hours (diuretic), 12-24 hours (antihypertensive). |
| Molecular Weight | 273.8 |
Hydrochlorothiazide 25 mg orally once daily in the morning. Maximum 100 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: 25 mg once daily. GFR 15-29 mL/min: not recommended. GFR <15 mL/min: contraindicated. |
| Liver impairment | Child-Pugh Class A or B: no adjustment. Child-Pugh Class C: use with caution, consider starting at 12.5 mg daily. |
| Pediatric use | Weight-based: 1-2 mg/kg/day orally divided every 12-24 hours, maximum 100 mg/day. |
| Geriatric use | Start at 12.5 mg daily; monitor electrolytes and renal function; may increase to 25 mg daily if needed. |
| 1st trimester | Hydrochlorothiazide crosses placenta. Not recommended in first trimester due to risk of teratogenicity and placental hypoperfusion. Reserpine is associated with increased risk of congenital malformations. |
| 2nd trimester | Hydrochlorothiazide may cause electrolyte imbalances and oligohydramnios. Reserpine increases risk of neonatal jaundice and respiratory depression. Use only if benefit outweighs risk. |
| 3rd trimester | Hydrochlorothiazide can cause fetal electrolyte disturbances, thrombocytopenia, and jaundice. Reserpine may cause neonatal bradycardia, respiratory depression, and hypothermia. Avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for HYDRO-SERP "25" (HYDRO-SERP "25").
| Placental transfer | Both components cross the placenta. Hydrochlorothiazide shows significant transfer. Reserpine also crosses and can cause adverse fetal effects. |
| Breastfeeding | Hydrochlorothiazide is excreted into breast milk in low amounts; may suppress lactation. Reserpine is also excreted and may cause neonatal gastrointestinal and respiratory effects. Avoid breastfeeding due to potential for serious adverse reactions in the infant. |
| Lactation Rating | Avoid |
| Teratogenic Risk | FDA Pregnancy Category D. Use of reserpine in the first trimester is associated with an increased risk of congenital malformations, including neural tube defects and cardiovascular anomalies. In the second and third trimesters, exposure may cause fetal bradycardia, hypothermia, and respiratory depression due to depletion of catecholamines. Chronic use may lead to fetal growth restriction. |
| Fetal Monitoring | Maternal: Baseline and periodic monitoring of blood pressure, heart rate, mental status, and gastrointestinal function. Fetal: Ultrasound for growth assessment and amniotic fluid volume; fetal heart rate monitoring during labor for signs of bradycardia. |
| Fertility Effects | Reserpine may impair fertility in both males and females by interfering with hypothalamic-pituitary-gonadal axis. Animal studies have shown reduced spermatogenesis and ovulation. Human data are limited, but reserpine use has been associated with menstrual irregularities and erectile dysfunction. |
■ FDA Black Box Warning
None
| Serious Effects |
AnuriaHypersensitivity to hydrochlorothiazide or reserpineHistory of depression or suicide attemptActive peptic ulcer diseaseUlcerative colitis
| Precautions | May cause electrolyte imbalance (hypokalemia, hyponatremia), May exacerbate systemic lupus erythematosus, Reserpine may cause mental depression, peptic ulcer, and nasal congestion, Photosensitivity, Orthostatic hypotension with reserpine |
| Food/Dietary | Avoid high-sodium foods to enhance antihypertensive effect. Limit alcohol intake as it may potentiate hypotension. Grapefruit juice may alter drug metabolism; avoid excessive consumption. Maintain adequate potassium intake (bananas, oranges) unless advised otherwise by your doctor. |
| Clinical Pearls | Hydro-Serp '25' contains hydrochlorothiazide 25 mg and reserpine 0.125 mg. Monitor serum potassium and magnesium; hypokalemia increases digitalis toxicity risk. Reserpine may cause mental depression; use with caution in patients with history of depression. Taper reserpine before surgery to avoid hypertensive rebound. Avoid concurrent use with MAOIs. |
| Patient Advice | Take exactly as prescribed; do not discontinue abruptly. · This medication may make you dizzy or drowsy; avoid driving until you know how it affects you. · Rise slowly from sitting or lying to prevent falls from low blood pressure. · Report any mood changes, depression, or vivid dreams to your doctor. · Use sunscreen and protective clothing; this drug increases sun sensitivity. · Do not use potassium supplements or salt substitutes without asking your doctor. |
Loading safety data…