How does pharmaceutical company marketing and promotion influence doctors' prescribing behaviour?

Key messages

• Gifts and payments from pharmaceutical companies to doctors increase inappropriate prescribing and the number of prescriptions doctors write, and probably increase the costs. Pharmaceutical company advertising and education may increase inappropriate prescribing and prescription costs; these activities probably increase the number of prescriptions doctors write.

• Conflict-of-interest policies that restrict or manage interactions between pharmaceutical companies and doctors probably improve prescribing appropriateness and may decrease the number of prescriptions.

• We need more studies investigating how free samples from pharmaceutical companies influence prescribing behaviour, and the effects on people's health of inappropriate prescribing.

What is pharmaceutical company marketing and promotion?

Pharmaceutical companies interact with healthcare professionals in a wide range of ways to promote the medicines they make. These interactions include visits from sales representatives, sponsored educational opportunities, direct mail, advertisements in medical journals, and sponsoring events at conferences. Pharmaceutical companies also provide doctors with gifts and payments, including food and drink, travel expenses, free samples, staff for clinics, and payments for being a member of a company advisory board.

What are the concerns about these interactions?

These interactions can help healthcare professionals learn about new treatments. However, pharmaceutical companies also want to increase sales of their products. This motivation may not always match the goal of prescribing the most appropriate or affordable medicine for each patient. There are concerns that these interactions influence doctors' prescribing decisions. Pharmaceutical companies spent almost 30,000 million US dollars on marketing and promotion in the USA in 2016.

What did we want to find out?

We wanted to find out whether interactions between doctors (and other healthcare professionals who prescribe medicines for patients) and pharmaceutical companies affect prescribing. We looked at four measures to answer this question:

• appropriateness: did interactions affect whether doctors prescribed medicines appropriately?

• quantity: did the number of prescriptions change?

• cost: did the cost of prescriptions change?

• did doctors' requests for medicines to be added to a hospital supply ('formulary requests') change?

What did we do?

We searched for studies that assessed how pharmaceutical company interactions with prescribers affected the appropriateness, quantity, and cost of prescribed medicines, and formulary requests, compared to no or fewer interactions.

We analysed the studies' results by organising the interactions into four groups:

• advertising and education;

• gifts and payments;

• free medicine samples;

• conflict-of-interest policies: rules that limit or manage interactions between doctors and pharmaceutical companies.

We rated our confidence in the evidence, based on factors such as study methods, the amount of evidence, and the strength of the patterns we observed.

What did we find?

We found 93 studies that addressed our question: 82 were carried out in the USA, and the remaining 11 in the UK and Europe. We found evidence addressing all four types of interactions:

• advertising and education (mainly sales representative visits to doctors): 16 studies;

• gifts and payments: 62 studies;

• free samples: 7 studies;

• conflict-of-interest policies: 8 studies.

Main results

Compared to no or less exposure, pharmaceutical company advertising or education aimed at doctors:

• may increase inappropriate prescribing (6 studies, 1335 doctors);

• probably increases the quantity of prescriptions (7 studies, 151,399 doctors);

• may increase the costs of prescriptions (2 studies, 986 doctors);

• may increase formulary requests, but the evidence was very uncertain (1 study, 105 doctors).

Gifts and payments from the pharmaceutical industry to doctors:

• increase inappropriate prescribing (10 studies, 2.9 million doctors);

• increase the quantity of prescriptions (39 studies, 3.8 million doctors);

• probably increase prescription costs (25 studies, 2.5 million doctors);

• may increase formulary requests, but the evidence was very uncertain (1 study, 105 doctors).

We are very uncertain if free medicine samples from pharmaceutical companies to doctors affect prescribing appropriateness, quantity, and costs, or formulary requests.

Conflict-of-interest policies that restrict or manage interactions between pharmaceutical companies and doctors:

• probably improve prescribing appropriateness (2 studies, 3065 doctors);

• may decrease prescribing quantity (6 studies, 110,470 doctors);

• have uncertain effects on costs (2 studies, 33,975 doctors).

None of the studies examining these policies measured changes to formulary requests.

What are the limitations of the evidence?

All the studies were carried out in the USA, UK, and Europe, so we do not know how pharmaceutical company marketing and promotion affects doctors' prescribing in other regions.

Because of the studies' methods, we cannot say that pharmaceutical marketing and promotion caused changes to doctors' prescribing. But we are confident that inappropriate prescribing was higher among doctors who received gifts and payments and that they wrote more prescriptions than doctors who did not receive gifts and payments. The studies also showed a consistent pattern: the more interactions doctors had with pharmaceutical companies, the less appropriate their prescribing was and the more prescriptions they wrote.

How up to date is this evidence?

The evidence is current to January 2025.