When you take tizanidine, a muscle relaxant used for spasticity and muscle spasms. Also known as Zanaflex, it works by calming overactive nerves in your spinal cord. and ciprofloxacin, a broad-spectrum antibiotic from the fluoroquinolone class used for urinary, respiratory, and skin infections. Also known as Cipro, it kills bacteria by disrupting their DNA repair. together, you’re mixing two drugs that can slow down how your body clears them both. This isn’t just a theoretical concern — it’s a real, documented risk that can lead to serious side effects.
The main problem? Both drugs are processed by the same liver enzyme system — CYP1A2. When ciprofloxacin is in your system, it blocks this enzyme like a clog in a pipe. That means tizanidine builds up faster and stays longer than it should. The result? Excessive muscle weakness, dizziness, low blood pressure, and in rare cases, a dangerously slow heart rate. One study in the Journal of Clinical Pharmacology found that when tizanidine was taken with ciprofloxacin, blood levels of tizanidine spiked by over 10 times. That’s not a minor interaction — that’s a red flag.
This isn’t just about taking them at the same time. Even if you space them out, ciprofloxacin lingers in your body for days. So if you start an antibiotic for a sinus infection and you’re already on tizanidine for back spasms, you’re still at risk. Some people feel fine — but others end up in the ER because they didn’t know. And it’s not just ciprofloxacin — other antibiotics like enoxacin and fluvoxamine can do the same thing. But ciprofloxacin is one of the most common culprits because it’s prescribed so often.
If you’re on tizanidine and your doctor prescribes ciprofloxacin, don’t assume it’s safe just because you’ve taken both before. Ask: "Can we switch to a different antibiotic?" or "What’s the lowest possible dose of tizanidine I can use while on this?" Some doctors will lower your tizanidine dose by half or more. Others might suggest a non-fluoroquinolone antibiotic like amoxicillin or doxycycline, which don’t interfere the same way.
And if you’re already taking both and feel unusually tired, dizzy, or your heart is pounding slower than normal — stop and call your doctor. Don’t wait. These signs don’t always show up right away. They can creep in over a few days. Your body doesn’t always warn you before things go wrong.
Below, you’ll find real-world cases, expert advice, and comparisons with other common drug interactions that can sneak up on you. No fluff. Just what you need to stay safe.
Nov, 18 2025
Combining tizanidine and ciprofloxacin can cause dangerous drops in blood pressure and extreme drowsiness. Learn why this interaction happens, who’s at risk, and what safer alternatives exist.