What medicine should you not take with nitrofurantoin?

October 12, 2025 •

4 min read

According to research, taking certain medications can significantly interfere with the effectiveness of antibiotics. Therefore, it is crucial to understand what medicine should you not take with nitrofurantoin, a common antibiotic used for treating urinary tract infections (UTIs). These interactions can lead to treatment failure or increase the risk of serious side effects.

Quick Summary

Several medications interact with nitrofurantoin, including magnesium-containing antacids, gout drugs like probenecid, certain live vaccines, and methotrexate. Avoid or carefully manage these combinations to ensure the antibiotic's effectiveness and prevent potential toxicity.

Key Points

Antacids with Magnesium: Avoid magnesium-containing antacids, like Gaviscon, as they can prevent the absorption of nitrofurantoin, making it ineffective for treating UTIs.
Probenecid: This gout medication can increase toxic levels of nitrofurantoin in the blood while decreasing its therapeutic concentration in the urine, so an alternative antibiotic is typically used.
Live Oral Vaccines: Nitrofurantoin can compromise the effectiveness of oral cholera and typhoid vaccines; separate doses of the antibiotic and vaccine are necessary.
Methotrexate: Taking nitrofurantoin and methotrexate together significantly increases the risk of serious and potentially life-threatening lung toxicity.
Impaired Kidney Function: Patients with significant kidney impairment should avoid nitrofurantoin due to the risk of drug accumulation and toxicity, including irreversible nerve damage.
Timing is Key: For some unavoidable interactions, such as with supplements containing magnesium, separating administration by at least 2-3 hours can help minimize interference.
Full Disclosure: Always provide your doctor and pharmacist with a complete list of all medications and supplements to prevent dangerous combinations.

The Purpose of Nitrofurantoin and the Risks of Interactions

Nitrofurantoin, known by brand names such as Macrobid and Macrodantin, is an antibiotic commonly prescribed for treating and preventing uncomplicated urinary tract and bladder infections. It works by targeting bacteria like E. coli within the urinary tract. However, interactions with other drugs can impact its effectiveness and safety. This can lead to decreased nitrofurantoin absorption and potential treatment failure, or increased levels in the bloodstream, raising toxicity risks.

Major Medications to Avoid with Nitrofurantoin

Certain medications pose a significant risk when combined with nitrofurantoin.

Antacids (Magnesium-Containing) Antacids containing magnesium, such as magnesium trisilicate, are a notable concern. Magnesium can bind to nitrofurantoin in the digestive system, reducing its absorption. Avoid magnesium-containing antacids while taking nitrofurantoin. If necessary, separate the doses by at least 2 to 3 hours, taking nitrofurantoin first. Alternatives like calcium carbonate-based antacids may have less interaction.

Gout Medications (Probenecid and Sulfinpyrazone) These medications, used for treating gout, affect how nitrofurantoin is processed by the body. Probenecid and sulfinpyrazone can prevent the kidneys from properly excreting nitrofurantoin. This can lead to increased nitrofurantoin levels in the blood, raising the risk of side effects, while reducing its concentration in the urine where it's needed to treat the UTI. An alternative antibiotic for your UTI is typically recommended if you are taking probenecid.

Live Bacterial Vaccines Nitrofurantoin can interfere with the effectiveness of certain live vaccines. The antibiotic action of nitrofurantoin can inhibit the growth of the live bacteria in vaccines like the oral cholera vaccine (Vaxchora) and oral typhoid vaccine (Vivotif). A waiting period is required after finishing nitrofurantoin before receiving these oral vaccines. Consult with your doctor regarding the appropriate timing. Injectable vaccines are not affected.

Methotrexate Methotrexate is a medication used for conditions like cancer and rheumatoid arthritis. Both methotrexate and nitrofurantoin carry a risk of lung toxicity. Taking them together significantly increases the likelihood of developing severe lung problems. This combination is generally avoided due to the increased risk of pulmonary toxicity. Your healthcare provider will assess the risks based on your medical history.

Quinolone Antibiotics Combining nitrofurantoin with quinolone antibiotics like ciprofloxacin or levofloxacin is not advised. Lab studies suggest that nitrofurantoin may reduce the antibacterial activity of quinolones. This could potentially decrease the effectiveness of both antibiotics if used together.

Colchicine Colchicine is used to manage gout attacks. Concurrent use of colchicine and nitrofurantoin may increase the risk of peripheral neuropathy, a type of nerve damage. Since both medications have this potential side effect, combining them could heighten the risk.

Fluconazole Fluconazole, an antifungal drug, may also interact with nitrofurantoin. Taking these medications together might increase the risk of serious lung and liver complications.

Comparison of Major Nitrofurantoin Interactions


Interacting Medication	Type of Interaction	Effect on Nitrofurantoin	Resulting Risk	Management Strategy
Magnesium-containing Antacids	Reduced absorption	Less drug absorbed	Treatment failure for UTI	Separate dosing by 2-3 hours; use alternative antacids
Probenecid	Inhibited excretion (renal)	Decreased urinary concentration, increased blood levels	Reduced UTI efficacy; increased toxicity	Use alternative antibiotic for UTI
Oral Typhoid/Cholera Vaccines	Antagonism against live bacteria	Decreased vaccine efficacy	No protection from vaccine	Separate vaccine and antibiotic administration
Methotrexate	Additive toxicity (pulmonary)	Increased toxicity risk	Serious lung problems	Combination typically avoided
Quinolone Antibiotics	Potential antagonism	Reduced antibacterial effect	Treatment failure	Not recommended for concurrent use
Colchicine	Additive toxicity (neuropathy)	Increased toxicity risk	Peripheral nerve damage	Discuss with doctor; monitor for symptoms

Considerations for Medical Conditions

Certain medical conditions also contraindicate the use of nitrofurantoin. Impaired renal function, or kidney disease, is a major concern. Nitrofurantoin requires adequate kidney function for proper excretion and to reach effective concentrations in the urinary tract. In individuals with significant kidney impairment, the drug can build up in the body, leading to toxicity. This accumulation increases the risk of side effects, particularly peripheral neuropathy. Additionally, insufficient drug may reach the urine to treat the infection effectively. Patients with significant kidney impairment should not take nitrofurantoin.

Managing Potential Interactions and Safe Use

Inform your doctor: Always provide your healthcare provider with a complete list of all medications, including over-the-counter drugs, vitamins, and supplements, before starting nitrofurantoin. Timing is key: If an interaction with a supplement like magnesium is unavoidable, separating the doses by several hours can help minimize the interaction. Monitor for symptoms: Be aware of potential side effects and report any unusual symptoms, such as numbness, tingling, or difficulty breathing, to your doctor immediately.

A Note on Over-the-Counter Medications and Supplements

Even non-prescription products can interact with nitrofurantoin. Magnesium-containing antacids are a primary example. Check the ingredients of any product for indigestion. Similarly, multivitamins or supplements containing magnesium should be taken at a different time than nitrofurantoin.

Conclusion

While nitrofurantoin is an effective treatment for many UTIs, understanding potential drug interactions and contraindicating medical conditions is vital for safe use. Key interactions to be aware of include those with magnesium-containing antacids, certain gout medications, and live bacterial vaccines. Furthermore, individuals with significant kidney impairment should avoid nitrofurantoin due to the risk of toxicity and reduced efficacy. Always communicate openly with your doctor and pharmacist about all your medications and health conditions to prevent adverse interactions and ensure successful treatment.

Frequently Asked Questions

You should not take magnesium-containing antacids, such as Gaviscon or Mylanta, at the same time as nitrofurantoin because they can significantly reduce the antibiotic's absorption and effectiveness. If you need an antacid, use one that does not contain magnesium, like Tums, and separate the dosing by a few hours.

Gout medications like probenecid and sulfinpyrazone interfere with your kidneys' ability to clear nitrofurantoin, leading to a build-up of the antibiotic in your blood (increasing toxicity risk) and lower levels in your urinary tract (reducing effectiveness).

Yes, you should be mindful of any supplements containing magnesium, as they can interact in the same way as magnesium-containing antacids. It is best to take nitrofurantoin at least two hours before or after taking a magnesium supplement.

Both methotrexate and nitrofurantoin carry a risk of pulmonary (lung) toxicity. Taking them together significantly increases the chances of developing serious lung problems, and the combination should generally be avoided.

Yes, nitrofurantoin can make certain live bacterial vaccines, like oral typhoid or oral cholera vaccines, less effective. A waiting period is required after completing your antibiotic course before taking these vaccines.

Nitrofurantoin relies on the kidneys to become concentrated in the urine. With impaired kidney function, the drug can accumulate in the body and cause serious side effects, such as peripheral neuropathy (nerve damage). In turn, it may not reach the urinary tract in high enough concentration to effectively treat the infection.

Quinolone antibiotics, such as ciprofloxacin and levofloxacin, may be less effective when taken with nitrofurantoin due to potential antagonism. It is best to avoid concurrent use of these different antibiotic classes.

Yes, always tell your healthcare provider about all medications, supplements, and vitamins you are taking. This information is critical for your doctor to check for potential drug interactions and ensure your safety and effective treatment.