Onset of Action for Oral Labetalol
Oral labetalol has an onset of action of 2-4 hours, with peak effects occurring within this timeframe. 1
Pharmacokinetic Properties of Oral Labetalol
- Labetalol is completely absorbed from the gastrointestinal tract with peak plasma levels occurring 1-2 hours after oral administration 1
- The duration of effect depends on dose, lasting at least 8 hours following single oral doses of 100 mg and more than 12 hours following single oral doses of 300 mg 1
- The maximum steady-state blood pressure response upon oral, twice-a-day dosing occurs within 24-72 hours 1
- About 70% of the maximum beta-blocking effect is present for 5 hours after administration of a single oral dose of 400 mg, with approximately 40% remaining at 8 hours 1
- The plasma half-life of labetalol following oral administration is about 6-8 hours 1, 2
Clinical Efficacy Timeline
- Labetalol given orally lowers blood pressure rapidly, with no evidence of tolerance to its antihypertensive action 3
- In hypertensive urgency studies, all doses (100 mg, 200 mg, and 300 mg) produced significant decreases in systolic and diastolic blood pressures at one, two, three, and four hours after dosing compared with baseline 4
- At two hours after dosing, diastolic blood pressure control was observed in 75%, 58%, and 67% of patients receiving 100 mg, 200 mg, and 300 mg respectively 4
- At four hours after dosing, diastolic blood pressure control was observed in 50%, 64%, and 67% of patients receiving 100 mg, 200 mg, and 300 mg respectively 4
Dosing Considerations
- For hypertensive urgencies, the European Society of Cardiology recommends oral labetalol as one of the first-line treatments 5
- In severe hypertension, including during pregnancy, intravenous labetalol is recommended as a first-line option 5
- The American Heart Association recommends that when using labetalol for hypertensive urgency, systolic blood pressure should be reduced by no more than 25% within the first hour 6
- For maintenance therapy, twice daily administration appears to be an acceptable compromise due to potential postural hypotension with large single doses 3
Important Caveats
- Postural hypotension is most likely to occur 2-4 hours after a dose, especially following large initial doses or upon large changes in dose 1
- Symptomatic postural hypotension is the most troublesome side effect of labetalol therapy 2
- Abrupt discontinuation of labetalol in patients with coronary artery disease can lead to exacerbation of angina, and in some cases, myocardial infarction and ventricular dysrhythmias 1
- Contraindications to labetalol include second or third-degree heart block, bradycardia, reactive airways disease, and systolic heart failure 7
Note on Cardio Excel
I do not have specific information about a medication called "Cardio Excel" in the provided evidence. Without knowing its active ingredient, I cannot provide information about its onset of action.