had episodes of waking in the night with heart racing and short of breath, also freezing cold, like a cold I can`t come out of.
I`ve had parasites for many years. Those cardiovascular symptoms and coldness (and there were many other symptoms too), happened when I was taking herbal anti-parasitics. It seemed to be a reaction to them being threatened. not sure if this helps you that much! but maybe knowing someone else has had the same reactions.
for me now, as I`ve learned in trying many things, if I get a reaction that doesn`t start to get better fairly quickly, I back off what I`m taking because when I didn`t before it did not help. I don`t know how it goes with rx though, I still haven`t taken it.