Peay and Peay in 1988109 clearly showed a relationship between seeing sales representatives and prescribing one new drug, and are often quoted by others. They interviewed 124 doctors in private practice, about their perceptions and use of temazepam, a benzodiazepine hypnotic, and their sources of information about it. The study was done in 1981, approximately a year after temazepam was introduced in Australia. They found that contact with a sales representative about temazepam most consistently predicted a favourable reception of temazepam at various points in the adoption process. Doctors who had seen a sales representative reported earlier awareness of temazepam, prescribed it earlier, were more likely to rate it as a moderate (rather than minor) advance over other drugs, were more likely to have prescribed it, reported prescribing it earlier, and were more likely to prescribe it routinely in preference to other alternatives. Compared to those who saw sales representatives less frequently, those who saw representatives more than once a week were aware of temazepam earlier, prescribed it earlier, and (amongst GPs) were more likely to prescribe it than other alternatives. Peay and Peay found no relationship between doctors’ professional involvement, or involvement in the medical community, and beliefs about temazepam. The study has considerable advantages over those described above. It does not ask doctors to assess themselves whether promotion has affected their decisions. It does not ask them to rate their own level of reliance on commercial information. The question “have you seen a sales representative regarding temazepam?” requests one simple fact that is likely to be easier for doctors to recall than the number of journal advertisements seen, etc. The group of GPs who had seen sales representatives about temazepam may have included more of the commercial information oriented doctors described above, but this is unlikely to account completely for Peay and Peay’s results.
In another important study Orlowski and Wateska110 analysed the effect on prescribing of drug company funded, all-expenses paid trips to educational symposia in resort locations. Using the hospital pharmacy inventory, they tracked the use of two drugs within one institution 22 months before and 17 months after each symposium about them. They also collected data on the national usage of these drugs, and informally interviewed the doctors who had gone to the symposia. Most of the doctors said that the symposia would not influence their prescribing, but some said that they might make them think of the drug more and the symposium might convince them of the benefits of the drug. Orlowski and Wateska found a dramatic and statistically highly significant increase in the use of the drugs in the hospital after the relevant symposia. These increases were not reflected in national data, and they did not seem to affect the hospital’s use of alternative drugs. This study provides evidence firstly, that exposure to promotion increases prescribing, and secondly that it can do so whether or not those exposed consider themselves vulnerable to such influence.
A useful study by Gönül et al.111 explored the impact of visits by sales representatives and samples, on prescribing. They used data from Scott-Levin Inc. (a company which describes itself as a leading pharmaceutical consulting firm) derived from survey sheets filled in by doctors. These included prescribing, minutes of detailing received for different drugs, and number of samples received, for a ‘typical’ week in each month, from January 1989 to December 1994. Gönül et al. looked at one condition and seven drugs used to treat it. Throughout the article it is unclear whether these were different drugs, or different brands of the same drug, and this is a major weakness of the study. Using a multinomial logit model, it appears that exposure to personal selling related to a medicine (visits from sales representatives and samples) increased the probability of that medicine being prescribed (other things being equal). However, the study also showed that excessive detailing or samples did not increase sales further, and that doctors who saw a high proportion of Medicare or Health Maintenance Organization patients were less influenced by promotion. The authors are from marketing schools, and they conclude that the study provides no evidence that personal selling has negative social consequences. There seems little evidence for this in the study. Part of the difficulty in evaluating the conclusion is that it is unclear whether the study examined seven brands of one drug, or seven drugs. The health consequences of changing drug therapy in response to marketing are likely to differ from those of changes in brand.
Research by Walton, a pharmacist and advertising executive, suggests that recall of print advertisements is associated with prescribing112,113. In one study published in 1980112 results are presented from a study of 1000 doctors in private practice who were shown print advertisements with drug and company names and logos blacked out. They were asked whether they had seen each advertisement before, and were then read a list of the advertised products and asked if they had prescribed or recommended these in the last month. For 95% of the advertisements the percentage of doctors who prescribed them was greater for those aware of the advertisements than for those not aware of them. However the effect of specialty was not controlled for. That is, doctors may be both more likely to notice and recall, and to prescribe, drugs relevant to their specialty. A similar study by Walton113 appears to be a smaller version or subset of this study.
Matalia120 reviews a range of advertising industry-related studies that claim to show the effectiveness of print advertising114-116. In the first, family practitioners and internists evaluated advertisements. ‘Prescribing data’ were also collected but it is unclear whether these are self-assessments of willingness to prescribe, or actual prescription data. Matalia claims that as non-prescribers became more familiar with the advertisements their willingness to write trial prescriptions increased. It seems from his earlier description that this study assessed correlations between attitudes and familiarity with advertisements, so he seems to be extrapolating from data collected at one point in time from a range of people, to trends over time. The account of the second study115 is somewhat more convincing, but again the methods and analysis are not described well enough for proper evaluation. The study was an experiment where different groups of doctors (who had prescribed similar numbers and value of prescriptions in the previous six months) were sent identical journals but with varying numbers of advertisements for a mature cardiovascular drug (i.e. one that had been on the market for some time). Those in the group who received the most advertising increasingly prescribed the drug. After 12 months the manufacturers market share was 4% higher in the high intensity and 2.3% higher in the medium intensity group, than in the lower group. The third study was also a kind of experiment. Companies stopped all promotion for four products from nine months before the study. Four advertisements were designed for the study and placed in half the copies of eight journals. Doctors were interviewed, and those who had received the advertisements were more likely to recall the products than those who had not. However, prescribing was not analysed: the outcome variable was simply recall of the products.
CONCLUSION: Exposure to promotion influences prescribing more than some doctors realise.