AMLODIPINE BESYLATE
Clinical safety rating: safe
Animal studies have demonstrated safety
Dihydropyridine calcium channel blocker that inhibits the influx of calcium ions across cardiac and vascular smooth muscle cell membranes, leading to vasodilation and reduced peripheral vascular resistance.
| Metabolism | Extensively metabolized in the liver via CYP3A4 to inactive metabolites. |
| Excretion | Metabolized extensively in the liver; 60% of metabolites excreted renally, 20-25% in feces; <10% unchanged in urine. |
| Half-life | Terminal elimination half-life 30-50 hours; steady-state achieved after 7-8 days; prolonged half-life allows once-daily dosing. |
| Protein binding | Approximately 93-98% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution 21 L/kg; large Vd indicates extensive tissue binding and distribution. |
| Bioavailability | Oral bioavailability 64-90% (mean 75%); not significantly affected by food. |
| Onset of Action | Oral: gradual onset, 2-4 hours to peak effect; full antihypertensive effect may take 2-4 weeks. |
| Duration of Action | Approximately 24 hours; supports once-daily dosing; antihypertensive effect persists for at least 24 hours after a single dose. |
Oral, 5-10 mg once daily. Initial dose: 5 mg once daily; maintenance dose: 5-10 mg once daily.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for any degree of renal impairment. Not removed by hemodialysis. |
| Liver impairment | Child-Pugh Class A or B: Initial dose 2.5 mg once daily; titrate cautiously. Child-Pugh Class C: Contraindicated or use with extreme caution (no established dosing). |
| Pediatric use | Age 6-17 years: 2.5-5 mg once daily. Weight-based: For hypertension, initial dose 0.1-0.2 mg/kg once daily (max 5 mg); titrate to max 10 mg/day. |
| Geriatric use | Initial dose 2.5 mg once daily due to decreased clearance and increased risk of hypotension; titrate slowly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Weak CYP3A4 inhibitors may increase levels but no dosage adjustment is typically needed Monitor for hypotension and peripheral edema dose-related side effects.
| Breastfeeding | Amlodipine is excreted into human breast milk at low concentrations; estimated infant dose is 1-6% of maternal weight-adjusted dose. M/P ratio not available. Most guidelines consider use compatible with breastfeeding; monitor infant for hypotension, somnolence, and poor feeding. |
| Teratogenic Risk | First trimester: No evidence of increased risk of major congenital anomalies based on prospective cohort studies; however, data are limited. Second/third trimesters: May cause fetal hypotension, reduced uteroplacental perfusion, and potential fetal hypoxia; animal studies show embryotoxicity and fetotoxicity at high doses. |
■ FDA Black Box Warning
None
| Common Effects | angina |
| Serious Effects |
["Hypersensitivity to amlodipine or any dihydropyridine"]
| Precautions | ["Peripheral edema","Hypotension","Worsening angina (rare, upon initiation or dose increase)","Hepatic impairment (use with caution, dose adjustment recommended)","Aortic stenosis (risk of increased risk of cardiovascular events)"] |
| Food/Dietary | Avoid grapefruit and grapefruit juice as they increase amlodipine levels and risk of hypotension. No other significant food interactions. Can be taken with or without food. |
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| Fetal Monitoring | Maternal blood pressure and heart rate; fetal growth assessment and amniotic fluid index via ultrasound; consider fetal non-stress test if used for hypertension in pregnancy. |
| Fertility Effects | In animal studies, no adverse effects on fertility at clinically relevant doses. No human data on fertility impairment. |
| Clinical Pearls | Titrate slowly in elderly patients to avoid hypotension. Avoid grapefruit juice. Use with caution in severe aortic stenosis. May cause peripheral edema, especially in higher doses. Monitor for gingival hyperplasia. Onset of action is gradual; may take 1-2 weeks for full antihypertensive effect. No dose adjustment needed in renal impairment. Diltiazem increases amlodipine levels; consider dose reduction. Amlodipine is a neutral drug in heart failure with preserved ejection fraction (HFpEF). |
| Patient Advice | Take exactly as prescribed; do not stop without consulting your doctor. · Swallow the tablet whole; do not crush or chew. · Avoid grapefruit and grapefruit juice while taking this medication. · Common side effects include swelling of the ankles or feet, headache, dizziness, and fatigue. · Report persistent or severe swelling, rapid weight gain, or shortness of breath. · Stand up slowly from sitting or lying to prevent dizziness. · Practice good oral hygiene to prevent gum swelling or tenderness. · May cause drowsiness; avoid driving until you know how the medication affects you. |