Clarithromycin Interaction Checker
Check Medication Interactions
This tool identifies potentially dangerous interactions between clarithromycin and other medications. Note: This is not a substitute for professional medical advice. Always consult your doctor or pharmacist.
Clarithromycin is a powerful antibiotic used to treat pneumonia, bronchitis, and skin infections. But here’s the problem: it doesn’t just kill bacteria. It also messes with how your body processes dozens of other medications. And in some cases, that mix can be deadly.
Why Clarithromycin Is Riskier Than Other Antibiotics
Most antibiotics don’t interfere much with other drugs. Azithromycin, for example, is a close cousin of clarithromycin-but it barely touches your liver’s drug-processing system. Clarithromycin? It’s a different story. It strongly blocks an enzyme called CYP3A4, which is responsible for breaking down about half of all prescription medications. When this enzyme is shut down, those drugs build up in your blood like a clogged drain. Levels can spike by 200% or more. That’s not just a side effect-it’s a medical emergency waiting to happen.The Deadliest Combo: Clarithromycin and Colchicine
If you’re taking colchicine for gout, this is the most dangerous interaction you need to know about. Colchicine is already a narrow-therapeutic-index drug-meaning the difference between a helpful dose and a toxic one is tiny. Clarithromycin can push colchicine levels up by nearly three times. The result? Severe muscle damage, kidney failure, diarrhea so bad it leads to dehydration, and multi-organ shutdown. There are documented cases where patients died within two weeks of starting clarithromycin while still on their regular colchicine dose. The FDA has recorded 58 serious or fatal cases of this interaction as of 2020, and experts believe the real number is much higher because many cases go unreported.A 76-year-old woman with chronic gout was prescribed clarithromycin for a respiratory infection. She kept taking her 0.6 mg daily colchicine. Eleven days later, she was dead. Her autopsy showed widespread muscle breakdown and organ failure. This isn’t rare. It’s predictable-and preventable.
Statins That Turn Deadly
Simvastatin and lovastatin are two cholesterol-lowering drugs that are especially risky with clarithromycin. These statins are heavily processed by CYP3A4. When clarithromycin blocks that pathway, statin levels skyrocket. That leads to rhabdomyolysis-a condition where muscle tissue breaks down and floods your bloodstream with toxic proteins. One case involved a 68-year-old man on 40 mg of simvastatin daily. After starting clarithromycin, he developed severe muscle pain and dark urine within 72 hours. He ended up in the ICU needing dialysis. Atorvastatin is also risky, though slightly less so. Rosuvastatin and pravastatin are safer alternatives because they don’t rely on CYP3A4.
Heart Medications That Can Trigger Lethal Rhythms
Clarithromycin doesn’t just raise drug levels-it can also directly affect your heart’s electrical system. It prolongs the QT interval, which is the time your heart takes to recharge between beats. When combined with other QT-prolonging drugs, the risk of a dangerous heart rhythm called torsades de pointes goes up by 2.7 times. This can lead to sudden cardiac arrest.Drugs like verapamil, diltiazem, and amiodarone are common culprits. Even common blood thinners like rivaroxaban can become dangerous when paired with clarithromycin. A pharmacist in a 2022 Medscape case report stopped a prescription where a 72-year-old with atrial fibrillation was about to get both clarithromycin and rivaroxaban. The patient was on multiple heart meds already. One wrong move could have been fatal.
Other Dangerous Pairings
- Digoxin: Clarithromycin can raise digoxin levels by up to 50%, leading to nausea, confusion, and dangerous heart rhythms.
- Ergotamine: Used for migraines. Combined with clarithromycin, it can cause severe blood vessel spasms, leading to limb ischemia or even amputation.
- Theophylline: An asthma drug. Levels can rise, causing seizures or irregular heartbeat.
- Warfarin: Clarithromycin can increase bleeding risk by interfering with how warfarin is broken down. INR levels can spike unexpectedly.
- Some seizure meds: Like carbamazepine and phenytoin. Toxicity can lead to dizziness, double vision, or coma.
Who’s at Highest Risk?
You’re not equally at risk for all these interactions. The danger spikes in certain groups:- People over 65: 42% of older adults taking clarithromycin are also on at least one dangerous medication. Their kidneys and liver don’t clear drugs as well, making buildup faster and more severe.
- Those with kidney disease: The European Medicines Agency specifically warns that clarithromycin and colchicine are especially deadly in patients with severe kidney impairment-risk increases by over four times.
- People on three or more medications: The American College of Physicians now recommends avoiding clarithromycin entirely in patients taking three or more drugs. The odds of a dangerous interaction jump dramatically.
What Should You Do Instead?
The good news? There are safer choices.Azithromycin is the clear alternative. It works just as well for most common infections-like sinusitis, strep throat, and bronchitis-but doesn’t block CYP3A4. Studies show it’s 2.8 times less likely to cause dangerous interactions than clarithromycin. Since 2015, azithromycin prescriptions have surged while clarithromycin use has dropped by 28%. Why? Doctors switched because they didn’t want to risk killing their patients.
If you’re on statins, ask your doctor if you can switch to pravastatin or rosuvastatin. If you have gout, ask if colchicine can be paused during your antibiotic course-or if another treatment like NSAIDs (if safe for you) can be used instead. Always check with your pharmacist before starting any new medication.
What to Do If You’re Already Taking Clarithromycin
If you’ve already started clarithromycin and are on any of the drugs listed above:- Stop taking the other drug immediately and call your doctor or pharmacist.
- Don’t wait for symptoms. Toxicity can hit fast-within 24 to 72 hours.
- Watch for signs: unexplained muscle pain, dark urine, severe diarrhea, dizziness, irregular heartbeat, confusion, or extreme fatigue.
- If you feel worse after starting clarithromycin, go to the ER. Don’t wait.
There’s no safe way to “just lower the dose” of colchicine or statins and keep taking clarithromycin. The interaction is too unpredictable. The only safe approach is to avoid the combo entirely.
Why This Keeps Happening
Even with all the warnings, these interactions still occur. Why? Because many doctors don’t check drug interaction databases before prescribing. Pharmacists are often the last line of defense. A 2023 FDA update added a boxed warning to clarithromycin labels-the strongest possible warning-about fatal colchicine interactions. But if the prescription slips through, the patient still suffers.The CDC and American Medical Association now recommend that clarithromycin be reserved for only a few specific infections, like Mycobacterium avium complex in immunocompromised patients. For most common infections, azithromycin is the better, safer choice.
Clarithromycin isn’t evil. It’s a useful tool. But like a chainsaw, it’s dangerous in the wrong hands-or in the wrong body. If you’re taking other meds, it’s not worth the risk.
Can I take clarithromycin if I’m on a statin?
No, not if you’re taking simvastatin or lovastatin. These statins can build up to toxic levels with clarithromycin, causing severe muscle damage. Atorvastatin carries some risk too. Safer alternatives include pravastatin or rosuvastatin. Always check with your doctor before combining any antibiotic with a cholesterol drug.
Is azithromycin always safer than clarithromycin?
Yes, for most people. Azithromycin doesn’t block the CYP3A4 enzyme, so it rarely causes dangerous drug interactions. It’s just as effective as clarithromycin for common infections like strep throat, sinus infections, and bronchitis. Unless you have a specific infection that requires clarithromycin-like Mycobacterium avium complex-azithromycin is the preferred choice.
What should I do if I’m on colchicine and need an antibiotic?
Tell your doctor you’re taking colchicine. They should avoid clarithromycin entirely. Azithromycin is the safest alternative. In some cases, your doctor may pause your colchicine during the antibiotic course. Never stop or adjust your dose without medical advice. Even one dose of clarithromycin with colchicine can be deadly.
Can I take clarithromycin if I have kidney problems?
Avoid it if you have severe kidney impairment, especially if you’re also taking colchicine or statins. Your body can’t clear these drugs properly, and toxicity builds up quickly. The European Medicines Agency warns that this combination increases the risk of fatal toxicity by over four times in patients with poor kidney function.
How do I know if a drug interacts with clarithromycin?
Ask your pharmacist. They have access to drug interaction checkers that flag over 140 contraindicated combinations with clarithromycin. You can also check the FDA’s updated labeling, which lists specific dangerous pairings. If a drug is metabolized by CYP3A4-like most statins, calcium channel blockers, and some antiarrhythmics-it’s likely risky. When in doubt, assume it’s unsafe.
Clarithromycin has a place in medicine-but only when no safer option exists. For most people, the risks far outweigh the benefits. Always ask: Is there a better antibiotic? Because sometimes, the safest treatment is the one you never take.
