I remember the first time, and if I did not know about tren cough Id have wanted an ambulance because it feels like a heart attack. It hits worse sometimes than others, then sometimes not at all. When it hits me it feels like an arrow going through my brain and like an elephant is sitting on my chest. If you stay calm though it will pass without trouble in about 2 minutes, maybe less. Just sit down and try to relax if it hits you. It hits quick, sometimes even before the plunger is all the way in, so if it hasn't hit you within a minute or two of your injection you got a " pass" .