At some point metoprolol (generic for
Toprol XL) became unavailable, was switched to brand name
Toprol XL, and have stayed with it since much fewer side effects, namely less "brain fog." My tachycardia seems to be set off by preservatives, incl sulfites/ates, nitrites/ates, flavor enhancers like monosodium glutamate, and red pepper flake. Black pepper in moderation doesn't seem to be a problem for me.