DO TOO MANY COOKS SPOIL THE BROTH - MULTIPLE PHYSICIAN INVOLVEMENT INMEDICAL-MANAGEMENT OF ELDERLY PATIENTS AND POTENTIALLY INAPPROPRIATE DRUG-COMBINATIONS

Objectives: To determine (a) whether the risk of a potentially inappro priate drug combination (PIDC) increases with the number of physicians involved in the medical management of an elderly patient and (b) whet her the risk of a PIDC is reduced if a patient has a single primary ca re physician or a single dispensing pharmacy, or both. Design: Cross-s ectional retrospective provincial database study. Participants: A regi onally stratified random sample of 51 587 elderly medicare registrants in Quebec who (a) visited at lease one physician in 1990, (b) were no t living in a health care institution for the entire year and (c) had been dispensed at least one prescription for a cardiovascular drug, a psychotropic drug or a nonsteroidal anti-inflammatory drug (NSAID). Ou tcome measures: information on all physician visits and drugs dispense d during 1990. Physician claims were used to identify the number of ph ysicians involved in a patient's management and whether the patient ha d one primary care physician. Prescription claims were used to identif y the number of PIDCs, prescribing physicians and dispensing pharmacie s. Results: The prevalence of PIDCs ranged from 4.0% (among those in t he NSAID group) to 20.3% (among those in the psychotropic drug group). Of the PIDCs identified, 17.6% to 25.8% resulted from contemporaneous prescribing by different physicians. The number of prescribing physic ians was the most important risk factor for a PIDC in all drug groups (odds ratio [OR] 1.44 to 1.71). The presence of a single primary care physician lowered the risk for cardiovascular and psychotropic PIDCs ( OR 0.70 and 0.79 respectively) but not for NSAID PIDCs (OR 0.94). The use of a single dispensing pharmacy lowered the risk of a PIDC in all drug groups (OR 0.68 to 0.79). Conclusion: The greater the number of p hysicians prescribing medications for an elderly patient, the greater is the risk that the patient will receive a PIDC. A single primary car e physician and a single dispensing pharmacy may be ''protective'' fac tors in preventing PIDCs.