Verapamil contained in Isoptin may increase the psychoactive effects of THC, so caution should be exercised when using such a combination.

A similar risk also occurs when combining beta-blockers with medical marijuana, more here:

https://www.gdziepolek.pl/opinie-i-pytania/95728/czy-jednoczesne-stosowanie-propranololu-i-medycznej-marihuany-jes

When it comes to the effectiveness of calcium antagonists and beta blockers – it is difficult to compare them in terms of which drug is stronger.
These preparations have different mechanisms of action.

Verapamil belongs to a class of drugs called calcium channel blockers. It works by relaxing the blood vessels so that the heart doesn't have to pump as hard. It also increases blood and oxygen supply to the heart and slows down electrical activity in the heart to control heart rate.

Beta blockers reduce the heart rate and its contractility, making it work slower and less intensively. As a result, the heart uses less blood and oxygen and is less likely to be deficient.

Beta-blockers usually work better in younger people, calcium antagonists in older people. However, this is not a rule – a beta-blocker will be recommended for a person with high plasma renin activity, a calcium antagonist with low calcium activity. It also depends on the response to treatment, e.g. during treatment with verapamil there is a high risk of persistent constipation; Beta-blockers increase the risk of erectile dysfunction (they can cause impotence, which disappears after treatment).

Here you can find more information about these drugs and make a reservation at the pharmacy:

https://www.gdziepolek.pl/produkty/38457/isoptin-sr-tabletki-o-przedluzonym-uwalnianiu/apteki

https://www.gdziepolek.pl/produkty/19583/concor-cor-2-5-tabletki-powlekane/apteki

I've attached links to helpful entries:

https://www.gdziepolek.pl/artykuly/czy-bac-sie-dzialan-niepozadanych-lekow

https://www.gdziepolek.pl/blog/odmiany-medycznej-marihuany