Cass, I'm just like this. Even if the panic attack is mild, it tires me in the same intensity. If the panic attack is severe, I tend to hibernate..... I know what you're saying by the drug thing. When I'm in this mode (haven't been in a while), I get weak, my limbs feel like there are weights attached. I basically sleep it off, sometimes for days. I attribute it partly to exhaustion, partly due to depression.