Are methotrexate and chlorithromycine used together?
Methotrexate can be prescribed with antibiotics when treating infections, but adding clarithromycin (the usual spelling is clarithromycin, sometimes misspelled “chlorithromycine”) can raise the risk of methotrexate toxicity. This interaction is a common safety concern clinicians check for before co-prescribing the drugs.
Why can clarithromycin be risky with methotrexate?
Clarithromycin can increase methotrexate levels in the body, which can lead to more side effects from methotrexate. Methotrexate toxicity can affect the bone marrow and the gastrointestinal tract, and in severe cases can become life-threatening.
Because both medicines can suppress parts of the immune system and affect blood counts, the combination needs closer monitoring than methotrexate alone.
What side effects should patients watch for?
Patients taking methotrexate with clarithromycin are typically advised to watch for signs of methotrexate toxicity, such as:
- Mouth sores (stomatitis)
- Severe nausea, vomiting, or diarrhea
- Fever or signs of infection
- Unusual bruising or bleeding
- Extreme fatigue or weakness (which can relate to low blood counts)
If any of these occur, patients should contact their prescriber urgently.
Can the interaction be managed?
Often clinicians can still use clarithromycin, but they may:
- Choose a different antibiotic if suitable
- Temporarily adjust dosing
- Increase blood test monitoring (commonly complete blood counts and liver/kidney tests)
- Review kidney function closely, since reduced kidney clearance increases methotrexate risk
The right approach depends on methotrexate dose (low weekly doses for autoimmune disease vs higher doses for cancer), kidney function, and the infection being treated.
Does this depend on the type of methotrexate treatment?
Yes. The interaction risk is generally higher when:
- Methotrexate is given at higher doses (for cancer)
- Kidney function is impaired
- Methotrexate is taken more frequently or at higher cumulative doses
- There are other interacting medicines
Are there alternatives to clarithromycin?
Depending on the infection and patient factors, clinicians may choose another antibiotic with less interaction potential. The “best” alternative depends on the bacteria suspected/confirmed and local resistance patterns.
If you tell me:
1) what methotrexate dose you take (and how often),
2) your kidney function status (if known), and
3) why clarithromycin is being used,
I can narrow down what clinicians usually consider in that specific scenario.