The Irish Medicines Board issued a recall for a batch of syringes this afternoon.
Clexane syringes were found to contain medication which was too concentrated.
Forty-six hospitals and 12 pharmacies had been supplied with the apparatus, which is used to treat patients with blood clots.
It had been on the market since December and up to 500 people may have been treated with the syringe.
Any patients who have the affected syringes with the batch number 28043 are advised to return them to their pharmacy and contact their doctor for advice immediately.