Dexamethasone
"Took one shot for a lung infection I received while doing some swimming. Fixed the lung infection but the side effects of this drug are very harsh so be prepared. 

I'm 25 do triathlons and swim regularly. Deal with a normal amount of stress and anxiety but have never had serious problems with it. Resting heart Rate is about 50 normally. 

After the shot resting heart rate was easily high 60's and low 70's. Extremely agitated and irritable. Very bad insomnia. Anxiety was out the roof and again I've never had problems with anxiety before. Chest pain mixed in with the increased anxiety that most likely made the chest pain felt worse but still it was a problem. This lasted for about a week as well. It's a serious drug."