Beta (β) blockers stop the action of epinephrine (adrenaline) and norepinephrine (noradrenaline) on so-called β-adrenergic receptors, part of the sympathetic nervous system which mediates the “fight or flight” response. If you feel this “skipped beat” every time you take your Propranolol, it is most likely an indication it has “kicked in” and started doing its job.