Inadvertent dispensing of Coumadin instead of Coversyl

the Editor: In August 2012, a 43-year-old woman presented to her general practitioner with extensive spontaneous bruising. Her only medications were Coversyl (perindopril) 5 mg daily for hypertension and Rhodiola rosea extract. Laboratory testing revealed prolonged coagulation times (Box 1). Mixing studies (50 : 50 patient and normal plasma) showed complete correction of the activated partial thromboplastin time and international normalised ratio (INR) and no evidence of a factor inhibitor on prolonged incubation. Results of liver function and lupus anticoagulant tests were normal. Plasma levels of vitamin K-dependent factors were reduced, consistent with vitamin K deficiency or inhibition (Box 1). The patient was administered 2 mg vitamin K orally; 48 hours later, her INR had fallen to 1.4. She denied taking warfarin or the structurally related brodifacoum (eg, Fast Action Ratsak), surreptitious administration of such compounds was not suspected, and she did not have a history of psychiatric illness.

The patient was referred to a haematologist for further evaluation. Visual assessment of the “Coversyl” bottle revealed that in fact Coumadin (5 mg warfarin tablets) had been dispensed 3 weeks before she initially presented to her GP (Box 2). She was advised to cease taking the medication immediately and the pharmacy was advised of the error.

In 2010, Melbourne Pathology had reported to the Therapeutic Goods Administration a series of incidents where Coversyl was inadvertently dispensed instead of Coumadin, leading to subtherapeutic INR results. Subsequently, the Coversyl bottle was produced with a white, rather than green, cap. The issue and the potential for adverse patient outcomes were communicated to pharmacies by the Therapeutic Goods Administration and Pharmacy Guild of Australia.1,2 Despite the modification and education, a further five patients across Melbourne, including this patient, were identified by Melbourne Pathology as having had Coumadin dispensed instead of Coversyl; these incidents were reported to the Australian Health Practitioner Regulation Agency by one of us (E L M) in August 2012.

Potential for confusion still exists, due to the alphabetical storage of medications on community pharmacy shelves (COUmadin is adjacent to COVersyl). Changes to pharmacy working practices, including mandatory scanning of bottle barcodes at the time of dispensing, and moving Coumadin to a different alphabetical storage area (under W for Warfarin) have been suggested. Practitioners should be vigilant in maintaining awareness of the possibility of warfarin being inadvertently dispensed instead of Coversyl or other medications if results of laboratory testing suggest vitamin K deficiency or inhibition.

2 Dispensing label (A) and bottle label (B) of the medication bottle inadvertently substituted for the prescribed Coversyl tablets