The Primary Reason: Weakened Immune Response
Methotrexate is a disease-modifying antirheumatic drug (DMARD) commonly used to treat autoimmune conditions like rheumatoid arthritis and psoriasis [1.5.2]. It works by suppressing the immune system to reduce inflammation and disease activity [1.3.1]. However, this same mechanism becomes a liability when the body needs to fight off an infection [1.2.1]. An active infection requires a robust immune response, but methotrexate dampens this capability, making it harder for the body to clear pathogens [1.2.2]. Continuing the medication can prolong the infection, increase the risk of complications, and potentially lead to more severe illness [1.2.2].
What Kind of Infections Warrant Stopping Methotrexate?
It is generally advised to temporarily discontinue methotrexate if you develop a moderate or severe infection that requires antibiotic treatment [1.4.4]. This includes a wide range of conditions:
- Systemic Infections If you feel systemically unwell with symptoms like a fever, chills, or sweating, the medication should be withheld [1.4.6, 1.2.6].
- Respiratory Infections Pneumonia and other significant respiratory infections are a key concern. Patients with rheumatoid arthritis on methotrexate have a higher risk of respiratory infections [1.2.8]. If you develop a new, persistent dry cough or shortness of breath, you should stop the medication and contact your doctor immediately, as this could also be a rare sign of methotrexate-induced lung inflammation [1.2.3, 1.2.6].
- Skin and Soft Tissue Infections These are among the more common types of infections seen in patients taking methotrexate [1.2.2].
- Urinary Tract Infections (UTIs) While a minor, uncomplicated UTI might not always require stopping the drug, a more severe or systemic UTI would [1.4.1, 1.4.6].
- Specific Viral Infections It is crucial to stop methotrexate and see a doctor if you develop or come into contact with someone who has chickenpox or shingles, as these infections can be very serious for someone on immunosuppressants [1.2.6, 1.4.4].
For minor infections, such as a simple cold without a fever, it may be appropriate to continue treatment, but the decision should always be made in consultation with a healthcare provider [1.4.1, 1.2.3].
The Dual Risk: Drug Interactions with Antibiotics
Another critical reason to pause methotrexate is the risk of interactions with antibiotics prescribed to treat the infection [1.2.2]. Certain antibiotics can interfere with how the body processes and eliminates methotrexate, leading to a toxic buildup of the drug [1.5.7].
- Penicillins: Antibiotics like amoxicillin and piperacillin can reduce the kidneys' ability to clear methotrexate, increasing its concentration in the blood [1.5.1, 1.5.3].
- Sulfonamides: Trimethoprim-sulfamethoxazole (found in drugs like Bactrim or Septra) should not be taken with methotrexate. This combination can lead to severe bone marrow suppression, even with low doses of methotrexate [1.5.5, 1.5.2].
- Tetracyclines: Antibiotics like doxycycline may also increase methotrexate levels [1.5.1, 1.5.6].
This potential for toxicity adds a second layer of danger to taking methotrexate during an infection. The combination can lead to severe side effects, including mouth sores, low blood cell counts, anemia, and bleeding problems [1.5.4].
Comparison of Risks: Continuing vs. Stopping Methotrexate During Infection
| Scenario | Risks & Considerations |
|---|---|
| Continuing Methotrexate | - Hinders the immune system's ability to fight infection [1.2.1]. - Prolongs the duration of the illness [1.2.2]. - Increases risk of serious complications and opportunistic infections [1.2.2, 1.3.7]. - Potential for toxic drug interactions with prescribed antibiotics (e.g., penicillins, sulfonamides) [1.5.2, 1.5.7]. - May mask or worsen symptoms of infection [1.2.2]. |
| Stopping Methotrexate | - Allows the immune system to mount a more effective response against the pathogen [1.2.2]. - Reduces the risk of severe, complicated, or prolonged infection [1.2.2]. - Avoids potentially dangerous interactions with antibiotics [1.5.1]. - Potential Downside: Risk of a temporary flare-up of the underlying autoimmune condition. However, this is often a manageable and secondary concern compared to an uncontrolled infection [1.6.1, 1.6.7]. |
The Process of Stopping and Restarting
Stopping methotrexate is straightforward; you do not need to wean off it [1.2.3]. It is typically recommended to withhold the medication for the duration of the antibiotic course and until you are feeling significantly better [1.4.1, 1.4.2, 1.4.5]. The medication can usually be restarted at the normal dose once the infection has fully resolved and any antibiotic treatment is complete [1.4.2, 1.4.7]. It is essential to communicate with your rheumatologist or prescribing doctor when you stop and before you restart the medication [1.2.3]. They can provide specific guidance based on your condition and the severity of the infection. In the event of a disease flare-up after stopping, your doctor might suggest treatments like NSAIDs or a short course of corticosteroids to manage symptoms [1.6.1, 1.6.2].
Conclusion
In summary, the decision to stop methotrexate during an infection is a crucial safety measure rooted in two primary concerns: allowing the body's suppressed immune system the chance to recover and fight the illness effectively, and avoiding potentially toxic interactions with antibiotics [1.2.2, 1.5.7]. While pausing treatment may carry a risk of a disease flare, this is generally considered a more manageable outcome than a severe, uncontrolled infection. Always consult with a healthcare professional before making any changes to your medication regimen.
For more authoritative information, you can visit the Versus Arthritis page on Methotrexate [1.2.6].
