IF I had seen this when you posted I would of responded right away...... I took 164mg to do some writing at this cafe.... I had NO idea the dosage I was taking... I thought it was equivalent to about 40mg of adderall or so.... I don't know how much your buddy took, but it was one of the scariest days of my life. It hit me many hours later, when I ate a small, last crushed piece I had left over and my heart started accelerating and my head became extremely hot and I the most horrible anxiety I thought I was gona die I just kept walking and walking and walking through the city.... bought an Ice Pack holding it on my head, drinking as much water as I could, I was trying so hard to hold it together I wanted to cry I really thought I was going to die. But I didn't want to call 911.
In retrospect, I should of called 911 right away. I ended up just walking for over 2 hours, met up with my mom, she drove me to the hospital because of my heart rate/extreme palpitations.
I ended up being OKAY and they sent me home with the prognosis of heart palpitations, but it was a fucking terrifying experience.
I also believe it caused some temporary damage because 4 or 5 days later, I had not taken anything at all since that time.... and out of nowhere, I had a couple sips of coffee, that's all I can think of. And I started to become increasingly dissociative and things got scary, idk hard to explain what im trying to say. I guess it's what you would call an extreme panic attack? And my heart rate started speeding up, ran back to my apartment, leaving my macbook there, lay down in bed tried drinking water - hoping it would pass... but it didn't and I started to have this feeling that I was going to have a seizure and my legs and arms began to shake uncontrollably so I called 911 and they rushed me to the hospital.....
FUCK CONCERTA, Be careful with that shit, it can be dangerous.
I hope you friend made it out okay.