Well I'm not a licensed health care provider (so please speak with your provider about the incident and do not take this as medical advice), but nifedipine is a calcium channel blocker, not a beta-blocker.
It has some of the same therapeutic effects, such as reduced blood pressure, so if you used far too much, that may have caused your episode.
The common side effects are dizziness, light-headedness, and hypotension.
If you're taking a beta-blocker such as propranolol in conjunction, the effects are compounded.
So, be careful and talk to your doc.
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