The Finnish Medicines Agency (Fimea) said Wednesday that some 30-50 lung cancer patients were given expired medication for treatment between spring and summer 2018. The exact number of patients is not known.
Labelling on a batch of the cancer drug Altima had been falsified before importation into Finland, according to Fimea.
The expiration date was marked as March, 2019 even though the actual last date of use was February, 2018.
The pharmaceutical watchdog called the situation "serious and exceptional". Expired medications can potentially produce harmful compounds or lose their efficacy.
Second case within months
However, Fimea said the medicine contained in the out-of-date Alimta batch corresponded to the legitimate drug and did not pose a health hazard.
Neither Fimea nor other European officials have been able to say who may have been behind the forgery or in which country the crime was committed.
The drugs were imported into Finland via the Danish firm Orifarm, whose Finnish office is located in Espoo.
The batch of Alimta is the second case of counterfeit cancer medication to make its way into patients' hands within a year.