Half-Life of Intraarterial Verapamil
The half-life of intraarterial verapamil is 2 to 5 hours, based on the terminal elimination phase following intravenous administration. 1
Pharmacokinetic Profile
The FDA-approved drug label for verapamil specifies that intravenously administered verapamil exhibits bi-exponential elimination kinetics with two distinct phases: 1
- Rapid distribution phase (alpha): approximately 4 minutes half-life 1
- Terminal elimination phase (beta): 2 to 5 hours half-life 1
Since intraarterial administration is functionally equivalent to intravenous administration in terms of systemic pharmacokinetics (both bypass first-pass hepatic metabolism), the same elimination half-life applies. 1
Supporting Research Evidence
Multiple clinical studies confirm this elimination half-life range:
- Intravenous verapamil studies in healthy volunteers demonstrate an elimination half-life of 2.0 hours after IV bolus administration (0.1 mg/kg). 2
- Pharmacokinetic analyses in normal subjects show a beta-phase half-life ranging from 3.7 to 4.8 hours after intravenous doses. 3
- Conventional formulation studies report a half-life (t1/2 beta) of 3-5 hours for intravenous verapamil. 4
Clinical Implications
Peak therapeutic effects occur within 3 to 5 minutes after bolus injection, reflecting the rapid distribution phase. 1 This rapid onset is why verapamil is effective for acute management of supraventricular arrhythmias when given intravenously or intraarterially. 5, 6
The relatively short elimination half-life means that:
- Drug effects are transient after single bolus administration 1
- Repeat dosing may be needed for sustained therapeutic effect 5
- Continuous infusion (5-15 mg/h) may be required for ongoing rate control 5
Important Caveats
The elimination half-life can be significantly prolonged in specific patient populations:
- Elderly patients: Aging may prolong the elimination half-life 1
- Liver cirrhosis: Half-life increases four-fold (from 3.7 hours to 14.2 hours) in cirrhotic patients 7
- Hepatic dysfunction: Severe liver disease can dramatically reduce verapamil clearance by 66% and increase half-life 8
Dose adjustments are critical in these populations to prevent accumulation and adverse effects, particularly hypotension and bradycardia. 9, 7