The 18-year-old man from Chelmsley Wood, Solihull, was taken to hospital on New Year's Day after partying at the Rainbow in Digbeth.
Three men and a woman have now been released from hospital after treatment.
Police believe class A pills were distributed inside the club by a woman and two men, one of whom may have been wearing a fluorescent jacket.
All five casualties went to the same nightspot on New Year's Eve or New Year's Day.
A clubber has died after taking a "bad batch" of drugs which hospitalised four others, police said.