On May 8, 2025, the European Medicines Agency (EMA) made an announcement that got many in the drug safety field talking. They decided to update the product information for medicines containing finasteride and dutasteride, warning about the risk of suicidal thoughts and behaviours.

But here’s where it gets interesting: there’s no clear proof that one of these medicines causes suicidal thoughts. So why did EMA act? Because both drugs work in similar ways, and that could signal a drug class effect.

What’s Going On With These Medicines?

Finasteride and dutasteride are both 5α-reductase inhibitors, a class of medicines used to treat conditions like an enlarged prostate and male pattern baldness. They work by lowering levels of a hormone called dihydrotestosterone (DHT), which can influence certain brain chemicals.

For finasteride, case reports and research have suggested a possible link to mood changes, including depression and suicidal thoughts. For dutasteride, EMA reviewed the data and concluded:

“Although it was not possible to establish a link between suicidal ideation and dutasteride based on the reviewed data, dutasteride works in the same way as finasteride, and therefore information about the mood changes seen with finasteride will also be added to dutasteride’s product information as a precaution.”

In short, while no clear link was found for dutasteride, the EMA decided it was safer to warn about possible mood changes. That’s the value of recognising a potential drug class effect.

When a Drug Class Effect Raises Concern

Sometimes, even without definitive proof for every medicine in a group, the fact that they work the same way is enough to raise red flags. A drug class effect means a side effect might occur with any drug in that family, not just the one where it was first reported.

These two medicines affect brain chemicals called neurosteroids that can influence mood. So, even though most reports so far involve finasteride, dutasteride could carry similar risks. That’s why EMA updated the information on both medicines – to keep doctors and patients informed, even if the science isn’t fully settled yet. It’s a clear example of how understanding a drug class effect helps manage uncertainty in pharmacovigilance.

Why Drug Class Effects Matter for Pharmacovigilance

This case is an essential reminder that we don’t always get crystal-clear answers in drug safety. Sometimes the signs are subtle, and the data imperfect. Waiting too long for absolute proof can mean missing a chance to protect patients.

Pharmacovigilance experts often face tough decisions. You might notice patterns in reports that raise questions. You might know that similar drugs can have similar effects. Ignoring early warning signs is risky – spotting a potential drug class effect early can make all the difference.

In this case, EMA chose caution. It was better to inform healthcare professionals and patients so they could make informed decisions rather than wait for more substantial evidence. This is how applying the concept of a drug class effect can help prevent future harm.

Drug Class Effect Beyond Finasteride and Dutasteride

We’ve seen drug class effect stories before. Think of statins and diabetes risk, fluoroquinolones and tendon problems, or SSRIs and suicidal thoughts in teenagers. Drug safety is moving beyond evaluating one medicine at a time. Now, we must consider entire classes of drugs and how they work together.

Recognising a drug class effect strengthens pharmacovigilance. It allows safety measures to be applied broadly and early, not just when a problem becomes impossible to ignore.

The Takeaway for Pharmacovigilance Specialists

Even when the data isn’t perfect, shared risks between similar drugs can quietly cause harm. Spotting these risks early and acting on them can make a big difference.

EMA’s decision shows how important it is to stay alert, trust our scientific instincts, and always prioritise patient safety. Understanding drug class effects is one of the most effective tools to protect patients.