Show 1367: How to Check Prescription Drugs

In this week’s interview, Dr. Aaron Carroll of Indiana University what we should consider when we evaluate prescription drugs. How do we know if the benefits outweigh the risks for us?

You may want to listen to it via your local public radio station or catch the live stream at 7 am EDT on your computer or smart phone ( Here is a link so you can find which stations carry our broadcast. If you can’t listen to the broadcast, you may want to hear the podcast later. You can subscribe through your favorite podcast provider, download the mp3 using the link at the bottom of the page, or listen to the stream in this post starting December 18, 2023.

How We Test Prescription Drugs:

Pharmaceutical companies spend years and millions of dollars to evaluate the drugs they develop. They then present the FDA with the results of at least two (rarely more) randomized controlled trials (RCTs) to provide evidence that the drug they want approved works and is not too dangerous. Parsing those RCTs is important, and we’ll discuss some of the most useful tools. But first, we ask Dr. Carroll about how people can use their personal experience to weigh the pros and cons of drugs.

In a Guest Essay for the Opinion section of the New York Times, Dr. Carroll’s own involvement in two issues that many people don’t understand is depression and obesity. He titled it What Obesity Drugs and Antidepressants Have in Common. What they have in common is not the mechanism of action, the chemistry or other properties determined by science. Instead, both can carry a stain. Americans often believe that one should eat less and exercise more if obesity is a problem. For depression, the attitude is often Cheer up! o Pull yourself up by your bootstraps. (Don’t think this is physically impossible; it’s a popular metaphor.)

Another similarity between antidepressants and new weight loss drugs: we don’t really know how they work. Yes, we have a name for an entire category of antidepressants that describes a purported mechanism, the selective serotonin re-uptake inhibitors. But research has not confirmed that these drugs actually fight depression by leading to a buildup of the neurotransmitter serotonin in the brain. (For more details on that, you can listen to Show 1318: Challenging Dogma About Alzheimer Disease and Depression.)

What difference does it make whether or not we know how a drug works? Perhaps the effect is primarily psychological. A person who does not understand how a drug affects the health condition in question may be reluctant to try it.

Personal Experience Helps When We Evaluate Prescription Drugs:

Ultimately, it’s the patients’ experience with the drug that matters. If a doctor prescribes a drug but the patient discovers that they are suffering from severe or unacceptable side effects while taking it, the judgment is that the drug is not helping. On the other hand, even if someone doesn’t expect much from a prescription, if it helps they will probably continue to take it. Described by Dr. Carroll attributes her reluctance to try an antidepressant as well as her anxiety about gaining her weight despite a good, careful diet. Using drugs to treat these problems improved his life.

Is It Fraud?

Some people feel that getting a prescription to treat depression or achieve weight loss is cheating. Oddly, they don’t seem to feel the same way about taking blood pressure pills, thyroid hormones or antibiotics. The important thing we need to consider is not whether a medicine is a fraud, but whether it helps. Does the benefit outweigh the risk? The answer may vary from one person to another, but RCTs offer some guidelines.

Statistical Tools to Evaluate Prescription Drugs:

Each research report will include some indication of how well the drug performed. Usually this is a comparison between people on the drug and those on the placebo. The issue is how often they suffer a particular bad outcome.

Absolute vs. Relative Risk Reduction:

Ideally, the report will give us actual numbers. How many people were in the trial and how many received treatment? Tallying the results across different groups and dividing by the number of people in the group yields an absolute risk. The difference between the groups shows absolute risk reduction.

That number is important, but it’s usually not the number you’ll see in a news account of the study. Reporters often emphasize relative risk reduction. Generally, this is a larger number, but without knowing the absolute risk of the condition, it is almost meaningless.

NNT and NNH:

Once you know the absolute risk reduction, you can calculate how many patients would need to take the drug for someone to get the benefit. This is called the Number Needed to Treat or NNT. The lower the NNT, the more likely a particular patient will benefit. In contrast, the Number Needed to Harm or NNH expresses the risk of a side effect associated with the use of the drug. Knowing what these numbers mean is critical when we are evaluating prescription drugs.

Ultimately, we want evidence-based medicine. Both experiments and experience provide important evidence to determine how beneficial a drug is.

This Weeks Guest:

Aaron E. Carroll, MD, MS, is a Distinguished Professor of Pediatrics at the Indiana University School of Medicine. He is Bicentennial Professor, Associate Dean for Research Mentoring, and Chief Health Officer of Indiana University. He blogs on health research and policy at The Incidental Economist and is a regular contributor to Opinion and the Upshot for The New York Times. The latest book by Dr. Carroll’s The Bad Food Bible: How and Why to Eat Sinfully.
The picture of Dr. Carroll is copyright Marina Waters.

Dr. Aaron Carroll

Listen to the Podcast:

The podcast of this program will be available on Monday, December 18, 2023, after the broadcast on December 16. You can stream the show from this site and download the podcast for free.

Download the mp3.

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