No recreational value, no additive effects from other drugs. For me the sedation from beta-blockers isn't even recreational and it's more of a lethargic 'zapped of energy' feeling rather than sedation one would expect from a benzo or antihistamine... there are much safer ways of achieving sedation if that's your main goal.
I've been on propanolol for the past month (switched from atenolol) and I'm also a daily opioid user. I can't say there's been any additive effects whatsoever besides potentiation of anti-hypertensive effects. 40mgs is a reasonable dose if your set on trying it out, but please don't attempt to catch a buzz by raising the dose ... the only thing you'll achieve by doing so is lightheadedness, bradycardia, and hypotension... especially when used with opioids.
