Digoxin-quinidine and digoxin-amiodarone interactions: frequency of occurrence and monitoring in Australian repatriation hospitals.

An extensive scrutiny of 19,460 patients' charts was carried out by clinical pharmacists in six Australian Repatriation Hospitals. The incidence of the prescribing of digoxin-quinidine and digoxin-amiodarone combinations was 0.18% and 0.22% of patients, respectively, giving an overall level of 0.4% (4/1000). For both combinations, digoxin was prescribed long term in 81% of the cases and quinidine or amiodarone recently added to digoxin therapy in 44% of patients identified. Therapeutic drug monitoring of digoxin therapy was initiated by clinical pharmacists in 41% of patients and resulted in modifications to digoxin therapy in 63% of this sub-group of patients. Quinidine and amiodarone therapies were also changed in nine patients. Of particular note was the number (15 or 58%) of dosage changes or therapy cessations made to digoxin therapy for patients also receiving amiodarone which occurred as a result of clinical pharmacist intervention.