PROPRANOLOL HYDROCHLORIDE & HYDROCHLOROTHIAZIDE
Clinical safety rating: caution
Animal studies have proved adverse effects but may be safe for humans
Propranolol is a non-selective beta-adrenergic receptor antagonist blocking beta-1 and beta-2 receptors, reducing heart rate, myocardial contractility, and renin release; hydrochlorothiazide is a thiazide diuretic inhibiting sodium and chloride reabsorption in the distal convoluted tubule.
| Metabolism | Propranolol: extensively metabolized via hepatic glucuronidation, CYP1A2, CYP2D6; Hydrochlorothiazide: not significantly metabolized, excreted unchanged. |
| Excretion | Propranolol: <1% excreted unchanged in urine; extensively metabolized in liver, metabolites excreted renally. Hydrochlorothiazide: ≥95% excreted unchanged in urine via renal tubular secretion. |
| Half-life | Propranolol: 3-6 hours (terminal half-life); can increase with hepatic impairment. Hydrochlorothiazide: 6-15 hours (terminal half-life); prolonged in renal impairment. |
| Protein binding | Propranolol: 90% bound primarily to albumin; Hydrochlorothiazide: 40-68% bound to albumin. |
| Volume of Distribution | Propranolol: 4 L/kg (highly lipophilic, extensive tissue distribution). Hydrochlorothiazide: 0.83-3 L/kg (distributes into erythrocytes, minimal CNS). |
| Bioavailability | Propranolol: 30% (high first-pass metabolism); increased with food. Hydrochlorothiazide: 65-70% (oral); food may increase absorption. |
| Onset of Action | Oral: 1-2 hours for antihypertensive effect; peak effect at 2-4 hours. Hydrochlorothiazide diuretic effect begins within 2 hours, peaks at 4-6 hours. |
| Duration of Action | Propranolol: 6-12 hours (antihypertensive); given twice daily. Hydrochlorothiazide: 6-12 hours (diuretic); duration up to 12 hours. |
Propranolol hydrochloride 40-80 mg/hydrochlorothiazide 25-50 mg orally twice daily. Maximum propranolol 640 mg/day, hydrochlorothiazide 50 mg/day.
| Dosage form | TABLET |
| Renal impairment | GFR 30-50 mL/min: reduce dose by 50% or extend interval. GFR <30 mL/min: avoid hydrochlorothiazide; use propranolol with caution at 50% dose. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce propranolol dose by 50%. Child-Pugh C: contraindicated due to propranolol accumulation. |
| Pediatric use | Not recommended for hypertension; use individual components. For propranolol: 1-5 mg/kg/day divided q6-12h (max 16 mg/kg/day). Hydrochlorothiazide: 2 mg/kg/day divided q12h. |
| Geriatric use | Start at lowest dose (propranolol 40 mg/hydrochlorothiazide 12.5 mg) twice daily; increase slowly. Monitor for orthostatic hypotension, bradycardia, and electrolyte disturbances. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Other drugs that lower heart rate or blood pressure can have additive effects Abrupt withdrawal may exacerbate angina pectoris or cause myocardial infarction.
| Breastfeeding | Propranolol: M/P ratio ~1.2; minimal excretion into breast milk, considered compatible. Hydrochlorothiazide: M/P ratio ~0.6; low levels, but may suppress lactation; use caution in nursing mothers. |
| Teratogenic Risk | Propranolol: First-trimester exposure associated with intrauterine growth restriction (IUGR) and preterm birth; second/third trimester: fetal bradycardia, hypoglycemia, and respiratory depression at birth. Hydrochlorothiazide: First trimester: non-teratogenic; second/third trimester: potential fetal electrolyte disturbances, neonatal thrombocytopenia, and jaundice. |
■ FDA Black Box Warning
No FDA black box warning.
| Common Effects | angina |
| Serious Effects |
["Bronchial asthma or COPD with bronchospastic component.","Sinus bradycardia, sick sinus syndrome, or heart block greater than first degree.","Cardiogenic shock or decompensated heart failure.","Anuria or hypersensitivity to thiazide diuretics or sulfonamides.","Pheochromocytoma (untreated)."]
| Precautions | ["Abrupt withdrawal may exacerbate angina or increase risk of myocardial infarction in patients with coronary artery disease.","May mask signs of hyperthyroidism and hypoglycemia.","Beta-blockers may worsen heart failure symptoms; avoid in decompensated heart failure.","Hydrochlorothiazide may cause hypokalemia, hyponatremia, hyperuricemia, and hypercalcemia.","May exacerbate renal impairment; monitor renal function.","Exacerbation of peripheral vascular disease."] |
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| Fetal Monitoring | Maternal: Blood pressure, heart rate, serum electrolytes, and renal function. Fetal: Ultrasound for growth (each trimester) and fetal heart rate monitoring; neonatal monitoring for bradycardia, hypoglycemia, and electrolyte imbalance. |
| Fertility Effects | Propranolol: No known significant effect on fertility. Hydrochlorothiazide: No direct studies; thiazides may cause electrolyte imbalances that could theoretically impair reproductive function. |