Multi‐dosage vials, potential for overdose

Iatrogenic overdosage is uncommon. However, vials containing multiple doses of drugs have the potential to cause serious overdose when the label can be easily misinterpreted. The current European Council Directive of medicinal products labelling (Chapters II to V, 65/65/EEC) states that the label of the drug should include a statement of the active ingredients of the product expressed quantitatively or qualitatively per dosage unit or according to the form of administration of a given volume or weight. At present there are no guidelines to prevent vials from containing more then one administration of the drug at any given time. Vials are often labelled with the amount of active ingredient per single unit (ml), rather than the amount in the whole container. Two recent incidents in our hospital brought this to our attention. The drug involved was Heparin, contained in a 5-ml vial. The highlighted label shows 5000 International Units ml−1 (IU ml−1) on one side and the total volume of 5 ml on the other side. This brings the total amount of Heparin in the vial to 25 000 IU. On two separate occasions, two patients were given 25 000 IU Heparin erroneously. The intention was to give only 5000 IU Heparin. This latter dose is the accepted loading dose for interventional procedures. In both incidents the medical practitioner believed that the entire vial contained 5000 IU Heparin and the total content of the vial (5 ml) was given. This resulted in significant morbidity that required transfusions and a surgical drainage of a haematoma. In neither incident were there were any long-term effects. On another separate occasion, this error resulted in death from cerebral haemorrhage. Nurses or doctors usually administer intravenous medicines in current hospital practice. Errors in drug administration are fortunately rare but can cause catastrophic complications. Careful reading of labels and double-checking of drugs should keep errors to a minimum. Nevertheless, misleading labels need to be highlighted as an easily correctable source of error. We suggest that the total dose (usually above lethal dose LD50) in the multidosage containers should be given more prominence, rather than the dose ml−1.