Drug-to-Drug Interactions: What You Don’t Know Can Hurt You

If you know me well, you know that I love music. I’ve experienced its evolution firsthand—from cassette tapes to CDs, mp3 players, and now streaming. Similarly, I’ve spent over 25 years educating patients about drug-to-drug interactions. Like the music industry, this field has evolved—but not always as swiftly as it should.

Let’s take a closer look at a familiar medication: Zoloft (sertraline).

Zoloft (sertraline), an SSRI antidepressant, was first introduced in the U.S. in 1991. While it wasn’t the first SSRI, it quickly became one of the most commonly prescribed antidepressants. Around the same time, millions of people were also being treated for thyroid conditions with levothyroxine. For decades, there was no widely recognized interaction between the two. Patients took them together, and prescribers generally felt confident in their compatibility.

But medicine—like music—keeps advancing.

Thanks to modern tools that analyze genetics, liver enzyme pathways, and individual metabolism, we now know that there may be a drug interaction for some individuals between sertraline and levothyroxine. The interaction has likely existed all along—we just didn’t have the knowledge or technology to identify it. In fact, many electronic drug monitoring systems still miss it today. I’ve seen this interaction firsthand in clinical practice, and it often takes the vigilance of an experienced clinician to spot and address it.

So, what’s the takeaway?

Don’t assume that long-term prescriptions are risk-free. Medicine is constantly evolving. What was once considered safe may reveal new risks as research advances.

To protect your health:

• Ask your pharmacist or prescriber for a current and comprehensive review of your medications.

• Don’t hesitate to raise concerns about drug interactions—even if your prescriptions haven’t changed.

• Recognize that each person’s body processes medications differently. Genetics, liver metabolism, and other individual biological factors can change how medications interact. What’s safe for one person may not be for another.

Your body—and science—are always evolving. Staying informed and advocating for personalized care is one of the most important things you can do for your health.