A surveillance image released by the Houston Police Department shows the suspect wanted in connection with the July 20 incident.
HPD said at about 10 p.m., a man and woman were sitting at a table at Rudyard's in the 2000 block of Waugh Drive.
When the man went to get a drink at the bar, police said the suspect approached the woman at the table, exchanged a few words, and left.
The other man returned to the table and finished the rest of the woman's drink. A few moments later, the man reportedly became ill but was not seriously hurt, police said.
According to HPD, the man took a drug test a few days later and said he tested positive for multiple prescribed meds he claimed he doesn't take.
The man and woman then filed a police report on July 24.
Anyone with information on this case is urged to call HPD at 713-308-8800 or Crime Stoppers at 713-222-TIPS.