It's unsafe to feed Any pets drugs. But seriously we don't use that hear or SWIM it doesn't give you legal protection and makes your post look stupid. Anyways don't use dxm on a stimulant comedown. Why are you so into otc drugs just curious?
It's not very safe, DXM is a pretty strong SNRI even at low doses and taking it with/after propylhexidrine (norepinephrine releasing agent, probably serotonin releaser too) can lead to hypertension, anxiety and panic, and in severe cases serotonin syndrome. At the very least I would expect its effects to be potentiated, especially the stimulating part of DXM.
haha, 300mg isn't gonna kill ya. Worst case scenario - you'll get some mild serotonin shit that lingers with you for a few days, which is not nice. I've been stuck in that 'syndrome' state after a decent DXM dose whilst taking Tramadol long term... I just forgot, I guess.
I'm no Doctor, but, it wasn't pleasant. Maybe 200mg on an empty stomach and some enhancers like a bit of erb?