Prescribing by habit and evidence

A recent Rolling Stone article on the over-prescribing of Eli Lilly’s anti-psychotic Zyprexa (olanzapine) started me thinking in a general way about the psychology of choosing what to prescribe.  I’ve written before about the effects of pharmaceutical marketing, how billions are spent to influence doctors’ prescribing habits at both rational and non-rational levels.  The Zyprexa article offers more on this topic.  But it also widened the issue for me as I reflected on my own prescribing.  For today I’ll let Big Pharma off the hook and look at other influences that affect prescribing.

Most doctors have “favorite” medications within a particular class that we prefer to prescribe.  Besides marketing influences, this can result from anecdotal experience:  If my last patient had a wonderful result on this drug, maybe my next will too.  Conversely, if my last patient had a terrible reaction, how can I risk giving the same drug to my next patient?  Such reasoning is unscientific yet very compelling.  First-hand outcomes are psychologically hard to discount, even when careful studies of large numbers of subjects provide far better evidence for the risks and benefits of a given treatment than anyone’s limited personal experience.  Likewise, the opinion of a trusted colleague (or attending physician, if one is a trainee) tends to make an impact regardless of the popularity of, or evidence base for, that opinion.

These are the sorts of biases that the evidence-based medicine (EBM) movement tries to stamp out.  According to EBM, we should base clinical decisions on the best available evidence, ideally large randomized controlled trials.  On the one hand, the need for Western medicine to declare itself “evidence-based” is almost an embarrassment; it should go without saying.  The scientific method is the bedrock of allopathic Western medicine.  It separates physicians from faith healers and snake-oil salesmen.

On the other hand, many areas of medicine lack the EBM gold-standard of randomized controlled trials (or the trials are inconclusive, conflict with each other, etc).  Studies of certain treatments, like dynamic psychotherapy, present severe methodological challenges. Randomized studies of invasive surgical procedures can be unethical.  Some studies are funded and others are not, for reasons having nothing to do with science.  Moreover, the results of randomized controlled trials are population averages, and individual patients do not always react the way the “average” patient does.  Fully evidence-based practice is an ideal, not possible in real life.

More important, both the prescribing physician and the patient are people, and we humans have feelings and preferences that affect our choices.  Doctors often prescribe particular drugs within a class purely out of habit.  The familiarity is comforting; dosing is easier, potential side-effects and interactions with other drugs are no surprise and are handled in stride. Experience prescribing one drug increases at the expense of familiarity with equally good alternatives.  Conversely, some physicians are “early adopters” who like to prescribe the newest product out.  While this is not my style, I assume the motivation is to be on the cutting-edge of the field.  The effect of the prescriber’s personality on treatment decisions sounds like a ripe area for research.  A brief PubMed search reveals a few interesting abstracts: 1, 2, 34.

Patients, too, have preferences, not only for heavily advertised products, but also for medications taken by relatives and friends.  And doctors, knowing that a patient’s belief in a treatment can aid its success, are inclined to prescribe what the patient asks for — if it is in the right ballpark.  Patients also weigh risks and benefits in personal ways.  One patient may disregard potential weight gain as a trivial concern, while another flatly refuses any treatment that can add pounds.  EBM can never account for such personal preferences.  (Some PubMed abstracts on patient attitudes and preferences: 1, 2, 3, 4.)

The prescribing of psychiatric medications is a combination of evidence-based medicine and the art of medicine.  The latter includes unfortunate biases — at times leading to overprescribing of medications such as Zyprexa — as well as essential sensitivity to psychological issues and patient preferences.  Until doctors are replaced by computers, and patients accept treatment without regard to individual preference, medicine will always reflect this combination.

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