Amlodipine’s intravenous (IV) conversion requires a clear understanding of its pharmacokinetic properties. Oral bioavailability is approximately 64-80%, varying slightly depending on the formulation. This means a significant portion of orally administered amlodipine is absorbed into the bloodstream.
Absorption and Distribution
Following oral administration, amlodipine absorption is relatively slow, reaching peak plasma concentrations in 6-12 hours. It’s extensively bound to plasma proteins (approximately 97.5%), primarily albumin. This high protein binding influences its distribution and elimination.
- This extensive protein binding is a key factor when considering IV administration, as it affects the free fraction available for pharmacological activity. Distribution into various tissues, including the heart, is relatively extensive.
Metabolism and Elimination
Amlodipine undergoes extensive hepatic metabolism, primarily via oxidation. The major metabolite, a pharmacologically inactive form, is then eliminated primarily through the kidneys (urine). A small portion is eliminated in feces.
Renal clearance is a primary route of elimination; therefore, impaired renal function necessitates dose adjustments. Hepatic impairment also modifies the amlodipine’s metabolism and subsequent elimination, requiring careful monitoring and potential dose modification.
Considerations for IV Conversion
The significant first-pass metabolism and high protein binding should be considered when converting from oral to IV amlodipine. Direct conversion using a simple dose ratio is inaccurate. Clinical judgment and potentially therapeutic drug monitoring are necessary to optimize dosing for IV administration. Individual patient factors, including age, liver and kidney function, will guide effective dose adjustments.
Half-life and Steady State
Amlodipine’s elimination half-life is approximately 30-50 hours. This prolonged half-life influences the time to reach steady-state concentrations (approximately 7-10 days). This long half-life means that dose changes will take time to reflect fully in the patient’s blood levels.
