MAOI Antibiotic: What It Is, Why It's Not Real, and What You Might Actually Need

There’s no such thing as an MAOI antibiotic, a class of drugs that inhibit monoamine oxidase enzymes and are used to treat depression, not infections. Also known as monoamine oxidase inhibitors, MAOIs are psychiatric medications—not antibiotics. They work by changing brain chemistry, not killing bacteria. Mixing them up can lead to serious, even deadly, side effects. If you’re searching for an MAOI antibiotic, you’re probably trying to understand a dangerous drug interaction—maybe you’ve been prescribed an antibiotic like trimethoprim or ciprofloxacin and are also taking an MAOI like phenelzine or selegiline. That’s a red flag.

MAOIs are old-school antidepressants, still used for treatment-resistant depression or panic disorder. But they’re tricky. They block enzymes that break down serotonin, norepinephrine, and dopamine. When those chemicals build up too fast—especially when you add another drug that affects them—you risk serotonin syndrome, a life-threatening condition caused by too much serotonin in the brain. Many common antibiotics don’t cause this on their own. But some, like linezolid, actually act as weak MAOIs themselves. Linezolid is an antibiotic for tough skin or lung infections, but it can trigger serotonin syndrome when taken with SSRIs, SNRIs, or true MAOIs. Even dextromethorphan (found in cough syrups) or certain pain meds can do it. It’s not about the antibiotic label—it’s about the chemical handshake between drugs.

Then there’s the confusion with trimethoprim, a common antibiotic often paired with sulfamethoxazole as Bactrim. It’s not an MAOI, but it can raise potassium levels dangerously—something people on antidepressants might not connect. And if you’re on an MAOI and get a UTI, your doctor might reach for trimethoprim without realizing you’re already walking a tightrope with your brain chemistry. That’s why knowing what you’re taking matters more than ever. The FDA warns about over 400 drugs that can mess with heart rhythms or serotonin levels. If you’re on an MAOI, you need to know every pill you take—even OTC ones.

You won’t find an MAOI antibiotic in any pharmacy. But you will find real cases where people got sick because someone assumed an antibiotic was safe to mix with their antidepressant. That’s why this page exists. Below, you’ll find real, detailed posts about how antibiotics like trimethoprim affect your body, how drug interactions can sneak up on you, and what you should ask your pharmacist before taking anything new. These aren’t theory pieces—they’re based on patient outcomes, FDA alerts, and clinical studies. If you’re on an MAOI, or know someone who is, what you read here could prevent a hospital visit.