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Data Collection
The interviewer administered the survey (in person or by telephone), using a standardized questionnaire with questions about relevant exposures and symptoms during the month before the survey date. The questionnaire consisted mostly of checklists and fill-in-the-blank entries; the interview lasted about 10 to 15 minutes. Data collected included demographic characteristics, indication for digox- in therapy, duration of digoxin therapy, dose of digoxin, disease states (e.g., symptoms potentially related to heart failure or atrial fibrillation or both), number and date(s) of hospital admissions in the previous month, concurrent illnesses (impaired renal function, malignancy, thyroid disorder, acute diarrhea), symptoms potentially related to digoxin toxicity (anorexia, nausea, vomiting, diarrhea, changes in vision, headache, weakness or dizziness, mental disturbances), dosage of nonprescription medications used in the past month, and whether usage patterns for nonprescription medications had changed over the past month. Participants were asked specifically about their use of 4 OTC products and 30 herbal supplements that have been reported as potentially interacting with digoxin (see Appendix 1) and about their use of any other nonprescription medications not specifically listed. In addition, patient-specific records in the provincial prescription database (PharmaNet) were reviewed to obtain information on the use of prescription medications during the month before the survey date.
Study Design and Setting
This open-label, cross-sectional survey study was approved by the University of British Columbia/ Providence Healthcare Research Ethics Board. Patients receiving digoxin therapy were recruited at St Paul’s Hospital, Vancouver, British Columbia, a 500-bed urban teaching hospital.
INTRODUCTION
Digoxin is commonly used to treat heart failure and atrial fibrillation.0 Its pharmacological effects include increasing the force of myocardial contractions, slowing the heart rate, and reducing the activity of the sympathetic nervous system. Most of the adverse effects of digoxin are dose-dependent, the most common being cardiac side effects, gastrointestinal disturbances, and central nervous system disturbances. Traditionally a therapeutic serum concentration range of 0.8 to 2 ng/mL (1.0 to 2.6 nmol/L) has been suggested, to prevent toxic effects that may occur at higher concentrations. However, recent studies have suggested a lower digoxin concentration range, 0.5 to 0.8 or 0.9 ng/mL (0.6 to 1.0 or 1.2 nmol/L), for treatment efficacy, especially for women with heart failure; in addition, to avoid potential toxic effects, it is now recommended that the serum digoxin level be less than 1.0 ng/mL (1.3 nmol/L) in patients with heart failure. Because digoxin is subject to various drug-drug interactions and because it has a relatively narrow therapeutic index, the dosage should be adjusted according to body weight, age, renal function, concurrent medications, and clinical observations.
Several previous studies have evaluated agreement between prescription records and interview-based medication history. However, those studies involved databases that were not centralized between pharmacies and were not available for general clinical applications beyond the individual pharmacy where the data were stored. In addition, dosing discrepancies were not reported, nor were reasons for discrepancies evaluated, in any of the studies reviewed. Sjahid and others17 evaluated the accuracy of information obtained from 1682 patients over 55 years of age in a Dutch population- based study database. These investigators found 80.4% concordance with interview-based medication history lists. Lau and others reported that 70% of medications present in a home inventory of 115 elderly patients were “active” according to pharmacy records and 96% were listed somewhere on the pharmacy record; however concordance was not calculated. In a study of antihyper- tensive drugs, there was full agreement between pharmacy records and a patient questionnaire for 321 (86%) of 372 patients interviewed. Read the rest of this entry »
More than 70% of the PharmaNet profiles reviewed for this study contained some inaccurate or misleading information about prescription medications currently consumed by the patients interviewed. These results suggest that sole reliance on PharmaNet profiles for medication histories could result in a high incidence of prescribing errors. Conversely, since it was relatively uncommon for a patient to be taking a medication that did not appear anywhere on the 14-month profile, PharmaNet provides an excellent starting point for medication reconciliation.
Of the 367 patients to whom letters were mailed inviting participation in the study, full medication history interviews were completed for 194 patients (52.9%) who had active PharmaNet profiles. The demographic characteristics of the study subjects are presented in Table 1. One hundred and thirty of the patients interviewed (67.0%) brought all of their prescription medications to the interview. On the basis of PharmaNet records and the patient interview, there was at least one difference in the list of medications currently consumed for 138 patients (71.1%; Table 2). Concordance between PharmaNet and the interview was 0.81 (95% confidence interval [CI] 0.77 to 0.84), and the proportion of medications from the interview that were active according to PharmaNet was 0.83 (95% CI 0.80 to 0.86). One hundred patients (51.5%) claimed to be taking at least one medication that was not listed in PharmaNet or was inactive according to the PharmaNet profile; 31 patients (16.0%) indicated that they were not taking at least one medication that appeared active on the PharmaNet profile. A higher number of currently consumed, regularly administered prescription medications identified during the patient interview was associated with a higher risk of discrepancies (odds ratio 1.31 per medication on the list, 95% CI 1.13 to 1.53; p < 0.001). The use of memory aids (pill boxes) was associated with fewer discrepancies (odds ratio 0.40, 95% CI 0.16 to 1.00; p = 0.05).
This cross-sectional cohort study evaluated agreement between medication lists obtained from a structured patient interview and from the PharmaNet profile available to British Columbia hospital pharmacists. This profile includes, in one comprehensive list, all active and inactive prescription medications filled at British Columbia community pharmacies during the previous 14 months, excluding drugs used to treat HIV (for historical reasons related to confidentiality). A cohort of patients with heart failure was selected as the study sample because these patients typically have a large number of similar prescription medications, and these complicated drug regimens often prompt hospital pharmacists to review PharmaNet for medication history information. All patients with current contact information who had an appointment at the St Paul’s Hospital Heart Function Clinic or the Pre Heart Transplant Read the rest of this entry »