From the FDA Drug Label
The apparent plasma half-life is about 10 hours Over a twenty-four (24) hour period, blood levels are fairly constant for about twelve (12) hours, then decline exponentially.
The duration of action of 20 mg propranolol is approximately 10 hours for its half-life, with fairly constant blood levels for about 12 hours after administration, then declining exponentially 1.
From the Research
The duration of action of 20 mg propranolol is approximately 3 to 6 hours, as indicated by its half-life, which requires multiple daily dosing to maintain therapeutic effects throughout a 24-hour period 2.
Key Points
- The half-life of propranolol is about 3-6 hours, explaining its relatively short duration of action 2.
- Propranolol undergoes extensive first-pass metabolism in the liver, reducing its bioavailability to about 25-35% 2.
- The medication begins working within 30 minutes to an hour after ingestion, with peak effects occurring around 1-1.5 hours after administration.
- For patients requiring longer coverage, extended-release formulations are available that provide 24-hour coverage with once-daily dosing.
- The duration of beta-blockade can vary somewhat between individuals based on factors such as liver function, age, and concurrent medications that might affect propranolol metabolism 2.
Clinical Implications
- Multiple daily dosing, usually 2 to 4 times per day, is typically required to maintain therapeutic effects throughout a 24-hour period.
- Individual variations in plasma binding and liver function can affect the duration of action and the required dosage of propranolol 2.
- Abrupt withdrawal of propranolol should be avoided due to the risk of rebound angina, arrhythmias, and infarction, and a tapering schedule should be used instead 2.