Influences on Prescribing Behavior in Diabetes

Tom G. Bartol, NP


November 28, 2016

Misunderstandings About Metformin

A recent study,[1] conducted by three pharmacists and a nurse, explores why only 65% of patients with newly diagnosed type 2 diabetes (T2DM) and only 25% of people with ongoing T2DM are prescribed metformin. Although metformin is recommended as a first-line treatment for T2DM, it is still underused by clinicians who manage patients with T2DM.

Using two focus groups with a total of 14 participants, including physicians, nurse practitioners, physician assistants, and pharmacists, the study explored situations in which clinicians were hesitant to prescribe or may have discontinued metformin use. These situations included renal insufficiency, heart failure, hepatic dysfunction, alcoholism, current or historical lactic acidosis, and manufacturer-listed contraindications. Despite a lack of scientific evidence supporting the precautions or contraindications to metformin use listed by the manufacturer, many clinicians were not comfortable prescribing metformin in the presence of a precautionary condition or contraindication.

After a brief educational presentation about the evidence on the risks associated with metformin, the investigators reassessed the clinicians' level of comfort in prescribing metformin to patients with T2DM and such coexisting conditions as renal insufficiency, heart failure, and contraindications. They found that the participants were more likely to use metformin in these patients.

The researchers concluded that the beliefs held by many clinicians about the risks associated with metformin use in T2DM are not consistent with the available evidence. They suggest that metformin use in patients with T2DM can be increased through clinician education to improve their level of comfort in using metformin in patients with renal insufficiency, heart failure, hepatic dysfunction, alcohol use, and lactic acidosis.


More than 50 different medications from eight different classes are marketed for the treatment of T2DM. Most guidelines recommend using metformin in first-line management of T2DM, but data show that the two most prescribed diabetes medications are brand-name drugs: Lantus® SoloSTAR® (insulin glargine) and Januvia® (sitagliptin), both of which made last year's list of the top 10 most prescribed brand-name medications.[2] Metformin, despite being the recommended first-line medication, does not seem to be used as often as some brand-name medications.

In the metformin study, after participating in an educational session, participants indicated that they would be more likely to prescribe metformin to patients who had conditions that the manufacturer identified as precautions or contraindications. Their decision to prescribe metformin, however, was based on hypothetical case studies, not actual patient situations.

In real-life situations, education about metformin may not have as much influence on prescribing practices as suggested by the study. Many alternatives exist for pharmacotherapy in diabetes, and other factors can influence a clinician's preference. One of these factors is exposure to industry pressure to prescribe newer, brand-name drugs. Although newer drugs have not been shown to improve outcomes compared with metformin, the high proportion of brand-name prescriptions raises the question of how much influence the pharmaceutical industry has on prescribing.

A study published in JAMA Internal Medicine[3] found that physicians who received one pharmaceutical industry-provided meal linked to the promotion of a brand-name drug were more likely to prescribe that drug. The prescribing increase after one meal was 18% for Crestor®, 70% for Bystolic®, 52% for Benicar®, and 118% for Pristiq®. The relationship was also dose-dependent, meaning that additional meals led to greater increases in prescribing the brand-name drugs.

Another study published in the British Medical Journal[4] looked specifically at industry influence on prescribing of brand-name diabetes drugs and oral anticoagulants. They reviewed the association between drug company payments to physicians (food, gifts, travel, grants, charitable donations) and prescribing of brand-name drugs, finding that for every $13.00 a drug company spent on a doctor, that doctor prescribed an additional 107 days of a brand-name diabetes drug. Such gifts as travel and consulting and speaking fees had a greater effect, being associated with 375 more days of filled brand-name prescriptions.

Precautions, coexisting conditions, and contraindications clearly can influence prescribing, but industry influence is also real. Although we like to think that we are not biased by the pharmaceutical industry, the evidence suggests otherwise.


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