A suitcase, also containing a laptop, clothing as well as the drugs - which could be dangerous if swallowed by anyone other than the prescribed recipient - was stolen on Saturday, 11th January between 11.38am and 12.43pm from a luggage rack on the service.
PC Richard Kane, the investigating officer on the case, said that the fact drugs were involved made it all the more important the bag was found.
“I would like to appeal to anyone who saw anyone acting suspiciously or steal a black suitcase on the 11.38am Langwith to Nottingham train on Saturday to please contact us as a matter of urgency,” he said.
“This medication could have very serious consequences if consumed by anyone other than the person it has been prescribed to, and could be especially dangerous if found by children.”
Anyone with information is asked to contact British Transport Police urgently on Freefone 0800 405040 or text 61016.
Alternatively, people can call Crimestoppers, anonymously, omn 0800 555111.
In all calls, please quote incident reference 251 of 11th Janaury, 2014.