bradycardia
3 interactions related to bradycardia
metoprolol + hawthorn
Hawthorn (Crataegus) has mild vasodilatory and heart-supporting effects that can add to the blood-pressure and heart-rate lowering of metoprolol, modestly increasing the chance of low blood pressure, a slow pulse, dizziness, or fainting. The interaction is pharmacodynamic (it happens at the receptor and tissue level), not metabolic, so taking the doses at different times does not prevent it.
diltiazem + grapefruit
Grapefruit inhibits intestinal CYP3A4, modestly and unpredictably increasing systemic exposure to diltiazem.
cbd + beta-blockers
CBD weakly inhibits CYP2D6, the liver enzyme that clears beta-blockers such as metoprolol, propranolol, and carvedilol, so in theory it could nudge their plasma levels up. CBD also has a mild blood-pressure-lowering effect of its own. Both actions point in the same direction as the beta-blocker, but the CYP2D6 effect is weak and its real-world clinical significance has not been demonstrated in humans.