Frontier police say that common smugglers are now using techniques perfected by drug traffickers.
They said they have found hidden compartments in the floor of public buses that contained contraband medicines. They also have found medicines hidden in the walls of truck trailers, they said.
The discoveries have been along the northern border with Nicaragua.
There is a steady trade in medicines from Nicaragua because they are cheaper and because Nicaraguans living in Costa Rica prefer medicines with which they are familiar.
The latest discovery of a hidden compartment in a bus involved a Nicaraguan man who is a resident of Costa Rica, said police. There were 2,500 tablets and 100 other items, police said.