Thirty-five per cent of the psychiatry trainees in Hodges’ study⁴ agreed that discussions with sales representatives did not influence their prescribing behaviour. This attitude was less prevalent among more senior trainees. Among the Canadian family medicine residents in the Sergeant et al.⁵ study, 34% agreed and 43% disagreed that sales representatives influenced their prescribing habits. In emergency medicine, Keim et al.¹⁰ found that 75% of programme directors, but only 49% of residents, believed that marketing techniques affect residents' prescribing practices. Seventy per cent of the Canadian doctors surveyed by Strang et al.¹³ agreed that sales representatives affected physicians’ prescribing habits. Thirty-one per cent of the internal medicine residency programme directors surveyed by Lichstein et al. were concerned, and 13% were very concerned, about the impact of sales representatives on the attitudes and prescribing behaviours of their residents¹⁴. Most directors of family practice residency programmes in the USA (56%) felt that the information and resources provided by sales representatives affected the prescribing of residents and practicing doctors¹⁷.

Bansinath et al.³⁵ state that only 5-6% of Indian cardiologists report that medical sales representatives had played a role in their decisions to prescribe brand or generic drugs. Sixty-three per cent of doctors in a Turkish city surveyed by Güldal and Semin²⁷ felt that information from sales representatives did not influence their prescribing. Those who found information from sales representatives reliable tended to report that this information had more influence on them.

American general practitioners surveyed by Pitt and Nel³⁶ rated sales representatives as the third most important influence on their prescribing decisions, advertisements as fifth and gifts as sixth. However, this study had a low response rate and excluded journal articles in the list of possible influences. Clinical pharmacists involved in family medicine residency programmes, surveyed by Hume and Shaughnessy³⁷, rated sales representatives, along with journal articles, as the third most important source of drug information influencing the prescribing of family medicine residents.

In Sigworth et al.’s³² study of resident doctors in Virginia in 2000, 91% reported that sales representatives had some effect on their prescribing. The authors suggest that this high rate could be the result of recent publicity and discussion on these issues, although the residents had not had formal educational sessions on drug promotion.

CONCLUSION: Many doctors denied that they were influenced by drug representatives: in three studies of residents 34, 49 and 91% believed they were affected, in three groups of programme directors 75, 31 and 56% did so. The available data suggest that doctors may be more willing to say that other doctors are influenced than they are themselves, but this remains a hypothesis.