Your body

Does caffeine interact with antidepressants?

By GyroscopeUpdated November 14, 20265 sources

With most medicines that have been studied alongside caffeine, it still clears at its usual speed. Fluvoxamine, an antidepressant, is the big exception. In a 1996 study of 8 healthy volunteers, it took caffeine’s half-life from 5 hours to 31.

Ask your prescriber before you change your caffeine because of a medicine, and never change or stop a medicine on your own because of your coffee.

People on an antidepressant often wonder whether their coffee is part of why they feel jittery or sleep badly. With most medicines, the caffeine side of that is unchanged. Fluvoxamine is different, because it slows down the liver’s clearing of caffeine a lot.

We’d ask your prescriber before mixing caffeine with fluvoxamine, and keep it small and early in the day if they say it’s fine. For other medicines, the usual caffeine advice applies.

The fluvoxamine study

Researchers gave 8 healthy volunteers 200 mg of caffeine, then gave them fluvoxamine (50 mg a day for 4 days, then 100 mg a day for 8 days) and gave the caffeine again. Their caffeine clearance fell from 107 to 21 mL a minute, about a fifth of what it was, and the half-life went from 5 hours to 31. The authors warned that caffeine taken during fluvoxamine treatment may lead to caffeine intoxication.

Which medicines change it

A 2021 analysis pooled caffeine data from 141 studies. It found that most substances don’t change how much caffeine builds up in the body, with three exceptions: fluvoxamine, and two antibiotics, pipemidic acid and norfloxacin, all of which slow its clearance.

What a 31 hour half-life does

On a typical 5 hour half-life, an 8 oz coffee at 8am leaves about 13 mg at 11pm. On a 31 hour half-life it leaves about 69 mg. And because each day’s caffeine isn’t gone by the next morning, one 8 oz coffee every morning for a week would leave about 160 mg in you at 11pm on day seven. That’s more than one and a half 8 oz coffees’ worth, built up from one small cup a day.

These numbers come from 8 people in one study. Your own half-life on fluvoxamine could be shorter or longer, which is why the prescriber is the person to ask.

Signs of too much

The FDA lists a faster heart rate, palpitations, high blood pressure, trouble sleeping, anxiety, jitters, an upset stomach, nausea and headache. If you notice these on any new medicine, tell the person who prescribed it, and mention your caffeine.

For everything else

If your medicine isn’t one of the three above, the half-life calculator and the cutoff clock work for you the same way they do for anyone else.