Accidental over-anticoagulation: Substitution error by a foreign pharmacy

OBJECTIVE: ro describe an episode of inadvertent and excessive anticoagulat ion caused by mistaken substitution of medication by a pharmacy outside the US. CASE SUMMARY: A 57-year-old white woman was found to have profound prolonga tion of her prothrombin time (56.9 sec) and international normalized ratio (22.18), with other coagulation parameters relatively normal. She had no pr ior history of bleeding diatheses and was not taking any prescribed anticoa gulants. Her coagulopathy rapidly corrected with the administration of fres h frozen plasma and vitamin K. After her medications were visually inspecte d, it was discovered that she had purchased her prescription medications fr om a pharmacy in Mexico and that she inadvertently had been taking a prepar ation of warfarin (proprietary name in Mexico, "Romesa") instead of the pre scribed ramipril for her hypertension (proprietary name in Mexico, "Ramace" ). After removal of the incorrect medication, she experienced no further pr olongation of her coagulation parameters. DISCUSSION: Medication errors contribute significantly to adverse events fo r patients. The frequency of different types of medication errors is review ed, and problems specific to the use of warfarin are detailed. Circumstance s that might lead to a patient seeking prescription medication outside of t he US are also discussed. CONCLUSIONS: The acquisition of prescription medications from pharmacies ou tside of the US can have adverse consequences, especially if the foreign na me of the medication is different from its American name, while sounding si milar to other medications that also might be dispensed in foreign pharmaci es.