Twenty-three of the 103 Vancouver physicians who met the inclusion criteria (22%) agreed to participate, as did 17 of their practice partners. In Sacramento, 38 of 62 physicians who were contacted agreed to participate (61%). The main reason provided for nonparticipation was workload.
In total, 78 physicians participated in the study: 40 in Vancouver (all family physicians) and 38 in Sacramento (14 general internists and 24 family physicians). The characteristics of participating patients and physicians are described in . More Sacramento physicians were male (74% v. 55% in Vancouver) and methods of remuneration differed, with most Vancouver physicians being paid on a fee-for-service basis and most Sacramento physicians being on salary. The number of years since graduation and the ratio of men to women did not differ significantly between participating and nonparticipating physicians in either city. Full-time Vancouver physicians saw more patients per week on average than Sacramento physicians, but more Vancouver physicians worked part time.
About 61% of consulting patients participated in the survey (n
= 1431: 683 in Sacramento, 748 in Vancouver) (). The samples were similar in self-reported health status and demographics; in both cities participant income was higher than average and more patients than expected were of European descent.14,15
More patients in Sacramento than in Vancouver reported partial prescription drug coverage by a third party; more Vancouver patients reported full or no prescription drug coverage.
Fig. 1: Patient participation in the study. *These were patients who were directed immediately to the examination room. †The difference was the result of the larger number of non-English speakers and children in Vancouver. ‡Other consists (more ...)
A similar proportion of patients failed to provide income information in the 2 samples (11%), and 7.6% of US patients did not report insurance coverage. Other data on patient characteristics were missing less than 5% of the time.
Attitudes towards the physician–patient relationship and medicines were similar: 75% of patients in each city believed that physicians and patients should have an equal say in treatment, and 14% of patients would go to another physician if their physician refused to prescribe a medicine they wanted. Over 80% of patients mentioned physicians, pharmacists or reference books as their preferred information source on health and medicines; around 1% in each setting listed advertising (data not shown).
Exposure to advertising
Patients in Sacramento were significantly more likely to have seen advertisements for over half of 7 listed products mentioned in the questionnaire and for all individual products except loratadine (Claritin), which is an OTC drug in Canada (). However, 87.4% of Vancouver patients had seen at least 1 DTC advertisement within the last year and 30% had seen advertisements for more than 10 products.
More Sacramento patients (8.2% v. 3.5% in Vancouver) mentioned advertising as contributing to their decision to consult their physician or their belief that they needed a diagnostic test or a medicine, or as an information source they used (adjusted odds ratio [OR] 2.6, 95% confidence interval [CI] 1.5–4.3). More patients in Sacramento also said that they had conditions that could be treated by an advertised drug (29.4% v. 21.9%: adjusted OR 1.4, 95% CI 1.1–1.8). Patients particularly identified their allergies as conditions that could be treated by an advertised drug: 88 (12.9%) in Sacramento compared with 42 (5.6%) in Vancouver.
Prescription drug requests
Sacramento patients were twice as likely to request medicines as patients in Vancouver and over twice as likely to request advertised drugs (). After eliminating 12 consultations in which requested drugs were prescription-only drugs in 1 country and OTC drugs in the other, request rates remained substantially different: 14.2% in Sacramento versus 8.8% in Vancouver (p < 0.01) (data not shown).
Advertising exposure was measured through the number of listed products a person had seen advertised, identification with an advertised condition and use of advertising as an information source. In Sacramento, all 3 measures were associated with a higher probability of DTCA drug requests. In Vancouver, only the use of advertising as an information source (3.5% of patients) was significantly associated with DTCA drug requests (). compares the number of listed drugs patients had seen advertised with their request rates (χ2 for linear trend = 18.5, p < 0.001).
Fig. 2: Proportion of patients who requested DTCA drugs by the number of listed products they remembered having seen advertised. Loratadine (Claritin) was omitted from this analysis, because it had over-the-counter status in Canada. DTCA = direct-to-consumer (more ...)
We tested the robustness of city of residence as an independent factor that might influence request rates by including it in the same model as these 3 measures of individual advertising exposure. The coefficient for city of residence became smaller and marginally nonsignificant when adjusted for advertising exposure (OR 1.5, 95% CI 0.9–2.6; p = 0.06); advertising exposure remained highly significant ().
Patients requested 37 different DTCA drugs, 7 of which were requested by ≥ 3 patients. One-quarter of Vancouver DTCA drug requests were for products advertised in Canada.6
The most commonly requested nonadvertised drugs were antibiotics, anxiolytic or hypnotic drugs, and cardiovascular drugs.
More patients in Sacramento than in Vancouver received 1 or more new prescriptions: 41.3% versus 24.9% (adjusted OR 2.1, 95% CI 1.6–2.8; p < 0.01) (). The prescribing rate was higher overall in Sacramento, but more Vancouver patients received 1 or more refills: 25% versus 18% (data not shown).
Physicians fulfilled most requests for prescriptions in both settings. In Sacramento 80% of patients who requested prescriptions received them, as compared with 63% in Vancouver (). The main difference was in the prescribing rate for requested nonadvertised drugs (81.4% v. 57.1%), although this difference was no longer statistically significant after adjusting for patient and physician characteristics (adjusted OR 2.2, 95% CI 0.8–6.2). Prescribing rates for advertised drugs differed less (77.6% v. 72.0%: adjusted OR 2.1, 95% CI 0.5–9.6).
Patients who requested medicines were very likely to receive 1 or more new prescriptions, either for the drugs they requested or alternatives. Indeed, for patients requesting DTCA drugs, the odds of receiving a prescription (for any drug) were 16.9 times those of patients who did not request a medicine (adjusted OR 16.9, 95% CI 7.5–38.2) ().
In order to judge physician confidence in treatment choice for each new prescription, we asked, “If you were treating another similar patient with the same condition, would you prescribe this drug?” We judged an answer of “very likely” to indicate confidence in treatment choice, whereas “possibly” or “unlikely” would indicate some degree of ambivalence. In both settings, physicians were more likely to express ambivalence about drugs patients had requested, particularly advertised drugs, than nonrequested drugs (adjusted OR for requested DTCA drugs 7.1 in Sacramento [95% CI 2.5–19.8], 14.5 in Vancouver [95% CI 2.6–81.4]) (). Physicians were also more likely to judge patients to be knowledgeable about a drug if they had requested it.