New warning for millions on drugs like fluoxetine and metoprolol

People taking two very common drugs have been warned that the effects can combine to trigger a fatal heart condition. 8.6 million people in the UK take antidepressants, and more than 50million are prescribed beta blockers for everything from anxiety to heart conditions.

But the two chemicals can combine with delayed results. New research found that combining the two drugs increased the risk of dangerously low blood pressure and abnormally slow heart rate. The study involved people taking beta blockers and SSRIs or SNRIs—the most commonly used antidepressants, which include fluoxetine, sertraline, venlafaxine, duloxetine, and bupropion.

The research found the highest risk with beta-blockers like metoprolol, carvedilol, and nebivolol. They are usually broken down in the liver by an enzyme called CYP2D6, but some antidepressants block that enzyme, meaning they will build up in the body at dangerous levels.

• Police give major update on missing round-the-world Brit sailor
• UK weather: Exact date 20C heat blast hits Britain as maps turn yellow - 10 hottest cities

The research found that combining the two types of drugs could lower blood pressure by up to 20 per cent and increase the risk of a slow heart rate by 25 per cent.

Low blood pressure can cause everything from dizziness to organ failure, and a low heart rate can cause cardiac arrest. The findings were announced at the American Heart Association's Hypertension Scientific Sessions 2025.

Study lead Dr Inshal Jawed said: "We expected interactions, but the magnitude—particularly between nebivolol and other beta blockers broken down by CYP2D6—was striking. Clinicians should be cautious when prescribing CYP2D6-metabolised beta blockers with SSRIs or other CYP2D6 inhibitors.

"Dose adjustment and close monitoring are key, while beta blockers less reliant on liver metabolism may be safer alternatives."

She said more investigatioon is now needed. Symptoms to watch for include dizziness, blurred vision, nausea, fainting, confusion, chest pain, extreme tiredness, shortness of breath and difficulty concentrating.