I take 10 mg (1 pill)of oxymorphone IV 4 times a day for recovering from back surgery. I tried shooting up two pills at once yesterday and it felt the same as shooting up one. But about 20 minutes later my back hurt really bad and; I started to get really cold;thirsty; and started shaking badly. This is what happens when I wake up in the morning and don't shoot up for a few hours; that's normal withdrawal. The only thing I could do to make it feel better was take a half long hour shower and it went away. Why would I have withdrawal from taking more* and it happening 20 min later when the drug was still in my system full force? Normally I don't feel with drawl until 12-15 hours after my last dose?