Amitriptyline and Clarithromycin: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 2, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Amitriptyline
Clarithromycin
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
Both amitriptyline (Elavil) and clarithromycin (Biaxin) can each affect your heart's electrical rhythm in a similar way. They can stretch out a part of the heartbeat called the QT interval. When you take them together, that effect can add up, which in rare cases could lead to an abnormal heart rhythm.
This concern is based more on theory than on lots of real-world cases, so please don't panic. But it's worth a quick call to your pharmacist or doctor before taking both. They can check whether this combination is right for you, pick a safer option if needed, or keep a closer eye on your heart. This is very manageable with your care team's help.
Effect: Additive QT-interval prolongation when amitriptyline is combined with clarithromycin.
- Mechanism: Both agents independently prolong cardiac repolarization (QT). This is a pharmacodynamic (additive) interaction, not a metabolic one. Neither is a prodrug here.
- Direction/magnitude: Increased QT-prolongation risk; magnitude not quantified. Clarithromycin has postmarketing reports of torsades de pointes and fatalities.
- Onset: Unspecified.
- Evidence: Theoretical, but severity rated major.
- Management: Avoid coadministration where feasible. If combined, obtain baseline/follow-up ECG, monitor electrolytes (K+, Mg2+), review other QT-prolonging drugs, and individualize therapy.
What happens
Increased risk of QT interval prolongation
Interaction Deep Dive
Do not administer clarithromycin together with other medications known to prolong the QT interval, since the effects on QT prolongation can be additive12. QT interval prolongation, along with rare instances of arrhythmia, has been linked to clarithromycin. During postmarketing surveillance, spontaneous reports of torsades de pointes have occurred among patients taking clarithromycin. Deaths have been reported2.
Why it happens (mechanism)
Additive QT interval prolongation
How to manage this interaction
Keep taking both medicines exactly as prescribed until you can speak with your care team. Do not stop either one on your own.
- Because both drugs can affect heart rhythm, your prescriber or pharmacist may choose a different antibiotic, or may monitor you more closely (such as an ECG and blood electrolytes) if both are needed.
- Mention any other medicines you take, since some also affect the QT interval.
- Get urgent care if you feel fainting, palpitations, dizziness, or an irregular heartbeat.
Your care team can tailor the plan to keep you safe.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) Clarithromycin has been linked to lengthening of the QT interval and uncommon instances of arrhythmia. Instances of torsades de pointes have been voluntarily reported through postmarketing surveillance in patients taking clarithromycin. Deaths have been reported 2.
Common questions
Can I take Amitriptyline and Clarithromycin together?
Amitriptyline and clarithromycin can each prolong the QT interval, and combining them adds to that risk, so check with your pharmacist or doctor before taking both together. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Amitriptyline and Clarithromycin interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Amitriptyline and Clarithromycin interaction managed?
Keep taking both medicines exactly as prescribed until you can speak with your care team. Do not stop either one on your own. Because both drugs can affect heart rhythm, your prescriber or pharmacist may choose a different antibiotic, or may monitor you more closely (such as an ECG and blood electrolytes) if both are needed. Mention any other medicines you take, since some also affect the QT inter… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Amitriptyline or Clarithromycin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (2)
- Product Information: BIAXIN(R) XL Filmtab(R) oral extended-release tablets, clarithromycin oral extended-release tablets. AbbVie Inc (per FDA), North Chicago, IL, 2018. DailyMed
- Product Information: VOQUEZNA(TM) TRIPLE PAK(TM) oral kit, vonoprazan oral tablets, amoxicillin oral capsules, clarithromycin oral tablets kit. Phathom Pharmaceuticals (per FDA), Buffalo Grove, IL, 2023. DailyMed
Keep reading about Amitriptyline
Keep reading about Clarithromycin
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist