Police were called to reports of a break-in at an ambulance in Greenock, shortly after 7am yesterday.
The items, which were in a bag, include medical equipment and prescribed medication.
Officers believe the robbery took place while the vehicle was parked in Dempster Street at around 3.50am.
Sergeant Stuart Drake, from Greenock Police Office, said: "These medicines, if taken without strict medical supervision, could have potentially fatal consequences.
"I would ask anyone who has been offered any medication or may know about their whereabouts to contact the police.
"I would appeal to anyone who may have been in the area, and either witnessed the theft, or has information to come forward."