Authorities have charged a GSK regional manager and 11 doctors for alleged bribery from 2010-2012.
GSK has disciplined one worker and said it is co-operating with the investigation.
Former GSK sales rep Jarek Wisniewski was very open about the process to the BBC. "We pay doctors, they give us prescriptions. We don't pay doctors, we don't see prescriptions for our drugs," said Wisniewski.
The probe adds to one that GSK is facing in China.