How Fast Does Verapamil Work?
The answer depends on the formulation.
I started on verapamil recently and just was wondering how fast I can expect it to work.
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):
"Racemic verapamil is released from Verelan PM by diffusion following the gradual solubilization of the water soluble polymer. The rate of solubilization of the water soluble polymer produces a lag period in drug release for approximately 4-5 hours. The drug release phase is prolonged with the peak plasma concentration (Cmax) occurring approximately 11 hours after administration."
Generally, verapamil ER products with this delayed release mechanism, which is known as COER-24 (Controlled-Onset-Extended-Release), are taken at bedtime to provide peak concentrations during the early waking hours, when blood pressure and heart rate are often at their highest.
If you are asking the onset of action of IV verapamil, it is within 1-5 minutes and generally lasts for 10-20 minutes, although per the prescribing information, can be much longer for some individuals.
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.
Verapamil (ver AP a mil) is a calcium-channel blocker, which affect the amount of calcium found in your heart and muscle cells.
It relaxes your blood vessels, which can reduce the amount of work the heart has to do and is used to treat chest pain caused by angina, high blood pressure, and controls heart rate in certain conditions.
Different verapamil products have varying recommendations regarding whether or not they need to be taken with food, so be sure to ask your pharmacist how to take your particular product.
Grapefruit juice however, should generally be avoided as it can increase concentrations of the drug, potentially increasing side effects.
More information about verapamil can be found here:
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