Clarithromycin Interaction Checker
Check if your medications interact dangerously with clarithromycin. Based on FDA warnings and medical guidelines.
Clarithromycin is an antibiotic that works well against certain bacterial infections - pneumonia, bronchitis, skin infections, and even some stomach bugs like H. pylori. But here’s the catch: clarithromycin doesn’t just kill bacteria. It also messes with how your body processes a whole lot of other medicines you might be taking. And when it does, the results can be deadly.
Why Clarithromycin Is Different
Most antibiotics don’t interfere much with other drugs. Azithromycin, for example, is a close cousin of clarithromycin and rarely causes problems. But clarithromycin? It’s a strong inhibitor of CYP3A4 - an enzyme in your liver and gut that breaks down about half of all prescription medications. When this enzyme gets shut down, drugs build up in your blood like traffic on a blocked highway. And when those drugs are already dangerous at high levels? That’s when things go wrong.Think of it like this: if you’re on a statin for cholesterol, your body normally keeps the dose in a safe range. But add clarithromycin, and that statin level can jump 300%. That’s not a typo. One study showed a 282% increase in colchicine levels after just seven days of clarithromycin. That’s enough to trigger organ failure.
The Deadliest Combo: Clarithromycin and Colchicine
Colchicine is used to treat gout and a rare condition called familial Mediterranean fever. It’s effective - but only if you don’t take too much. The difference between a helpful dose and a lethal one is tiny. And clarithromycin turns a safe dose into a poison.The FDA has documented 58 serious or fatal cases of colchicine toxicity linked to clarithromycin as of 2020. Real people. Real deaths. One case: a 76-year-old woman with chronic gout took her usual colchicine pill. Then she got a respiratory infection and was prescribed clarithromycin. Eleven days later, she died from multi-organ failure. Her kidneys and muscles shut down. She didn’t even have time to realize what was happening.
These aren’t rare outliers. In 2023, the FDA added a boxed warning - the strongest possible alert - to clarithromycin’s label. It says plainly: “Concomitant use has resulted in fatal and near-fatal colchicine toxicity.” If you’re on colchicine, even once a week, clarithromycin is off-limits.
Other High-Risk Drugs to Avoid
Colchicine isn’t the only danger. Clarithromycin can turn common, everyday medications into ticking time bombs. Here are the big ones:- Statins - especially simvastatin and lovastatin. These can cause rhabdomyolysis - a condition where muscle tissue breaks down and floods your kidneys with toxic debris. One man, 68, on simvastatin 40mg daily, developed life-threatening rhabdomyolysis within 72 hours of starting clarithromycin. He needed ICU care and dialysis.
- Calcium channel blockers - like amlodipine, verapamil, diltiazem. These are used for high blood pressure and heart rhythm issues. When clarithromycin slows their breakdown, your blood pressure can crash. Your heart can slow to dangerous levels.
- Antiarrhythmics - drugs like quinidine or amiodarone. These already affect your heart’s electrical system. Add clarithromycin, and you raise the risk of torsades de pointes - a chaotic, deadly heart rhythm. The American Heart Association says clarithromycin increases this risk by 2.7 times compared to safer antibiotics.
- Immunosuppressants - cyclosporine, tacrolimus. Used after transplants. Too much can wreck your kidneys. Too little can cause rejection. Clarithromycin throws both sides out of balance.
- Anticoagulants - rivaroxaban, apixaban. These thin your blood. Clarithromycin can make them too strong, leading to internal bleeding. There’s at least one documented case where a pharmacist caught this combo before it reached the patient.
Why Elderly Patients Are at Highest Risk
Older adults are the most likely to be on multiple medications - and the least likely to survive a bad interaction. A 2023 study found that 42% of people over 65 taking clarithromycin were also on at least one dangerous drug. That’s more than four in ten. Compare that to azithromycin, where the number is just 28%.The American Geriatrics Society’s Beers Criteria - the gold standard for safe prescribing in seniors - now explicitly says: Avoid clarithromycin in patients 65+ who are taking CYP3A4 substrates with a narrow therapeutic index. That’s a fancy way of saying: don’t give it to older people on drugs where the dose is a razor’s edge.
And it’s not just about pills. Many seniors have reduced kidney function. That makes things worse. The European Medicines Agency warned in 2020 that patients with severe kidney problems who take colchicine and clarithromycin together have a 4.3-fold higher risk of death.
What You Should Do - Before You Take It
If your doctor prescribes clarithromycin, ask these questions:- “Am I taking anything that could interact with it?” - List every pill, supplement, or herbal product you use. Even over-the-counter ones.
- “Is there a safer alternative?” - Azithromycin is almost always a better choice. It works just as well for most infections and doesn’t wreck your other meds.
- “Can we check my kidney function?” - If your kidneys aren’t working well, the risk skyrockets.
- “Can you check my drug list with a pharmacist?” - Pharmacists use tools that flag 142 contraindicated combinations with clarithromycin. Use them.
The Mayo Clinic’s interaction checker flags 38 drugs as absolutely off-limits. The NHS UK says: “Tell your doctor if you’re taking any of these medicines before you start clarithromycin.” - and lists colchicine, statins, digoxin, warfarin, and epilepsy drugs. Don’t wait. Speak up.
What If You’re Already Taking It?
If you’re already on clarithromycin and you take any of these drugs, don’t stop either one on your own. Call your doctor or pharmacist immediately. They may:- Switch you to azithromycin
- Pause your statin or colchicine for the duration of the antibiotic
- Reduce your dose of the other drug by 50-75%
- Monitor you for muscle pain, weakness, confusion, or irregular heartbeat
Signs of trouble: unexplained muscle pain, dark urine, nausea, vomiting, dizziness, or a fluttering heart. If you feel any of these, get help now. Don’t wait.
The Bigger Picture: Why This Is Happening
Clarithromycin prescriptions have dropped 28% since 2015. Why? Because doctors are waking up. In 2022, a survey of 1,200 U.S. physicians found that the #1 reason they switched from clarithromycin to azithromycin was “fewer drug interactions.”Pharmaceutical companies are even working on a new version of clarithromycin with less enzyme inhibition - but it won’t be out until 2026. Until then, the safest move is to avoid it.
Clarithromycin isn’t going away. It still has its uses - like treating Mycobacterium avium complex in people with HIV. But for most common infections? It’s outdated. It’s risky. And in too many cases, it’s deadly.
Can I take clarithromycin if I’m on a statin?
No - not if it’s simvastatin or lovastatin. These statins are broken down by CYP3A4, and clarithromycin stops that process. The result can be severe muscle damage (rhabdomyolysis), kidney failure, or death. Atorvastatin is less risky but still requires caution. Azithromycin is the safer antibiotic choice if you’re on statins.
What should I do if I accidentally took clarithromycin with colchicine?
Call your doctor or go to the emergency room immediately. Symptoms of colchicine toxicity include severe diarrhea, vomiting, muscle pain, weakness, and confusion. These can appear within days. There’s no antidote - treatment is supportive: IV fluids, kidney monitoring, and sometimes dialysis. Early action saves lives.
Is azithromycin always a better choice than clarithromycin?
For most common infections - like sinusitis, bronchitis, or pneumonia - yes. Azithromycin works just as well and has minimal CYP3A4 inhibition. It’s the preferred macrolide in guidelines from the American College of Physicians (2024) for patients on three or more medications. Only in rare cases - like Mycobacterium avium complex - is clarithromycin still essential.
Can I take clarithromycin with over-the-counter medicines?
Some OTC drugs can interact. Antacids with magnesium or aluminum can reduce clarithromycin absorption - take them 2 hours apart. Herbal supplements like St. John’s Wort or grapefruit juice can also affect how clarithromycin works. Always check with a pharmacist before mixing any OTC product with antibiotics.
Why isn’t clarithromycin banned if it’s so dangerous?
It’s not banned because it still has life-saving uses in specific cases - like treating tuberculosis-related infections or Mycobacterium avium complex in immunocompromised patients. The risk is real, but so is its benefit in those narrow scenarios. The solution isn’t removal - it’s awareness. Better screening, better prescribing, and better patient education.
