Dane asked
I started on verapamil recently and just was wondering how fast I can expect it to work.
At a glance
- Immediate release verapamil products begin to work in 1 to 2 hours. Most extended release products take about the same amount of time. However, extended release verapamil products that utilize the COER-24 system (e.g. Verelan PM) don't begin working until 4 to 5 hours after dosing.
Answer
Verapamil, a calcium channel blocker, is available in a variety of formulations, each with a different onset of action.
According to the prescribing information, immediate-release verapamil products will begin to work 1 to 2 hours after taking a dose by mouth.
Most extended-release verapamil products will take around the same amount of time to start working (1 to 2 hours), but take far longer to reach maximum concentrations, around 5 hours (10-11 hours for some products).
It is important to note, however, that there are many different extended-release verapamil products, some of which have different characteristics.
One such product is Verelan PM (and associated generics), which has a delayed-release mechanism.
After taking a dose by mouth, the active ingredient (verapamil) in Verelan PM isn't released for 4 to 5 hours, meaning it will take that long to start working.
Per the prescribing information for Verelan PM (verapamil extended-release capsules):
