Understanding Mefenamic Acid
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) prescribed to treat mild to moderate pain, including menstrual pain (dysmenorrhea) [1.5.1]. It works by blocking the production of prostaglandins, which are substances in the body that cause pain and inflammation [1.5.1]. While effective, mefenamic acid carries a risk of serious side effects, particularly when mixed with other substances. It's essential to use this medication under a doctor's supervision, at the lowest effective dose, and for the shortest possible duration [1.6.1].
Major Drug and Substance Interactions to Avoid
Combining mefenamic acid with certain medications and substances can lead to severe health complications. An interaction occurs when another substance alters how a drug works, which can be harmful or reduce the drug's effectiveness [1.2.1]. Always inform your healthcare provider of all medications, supplements, and herbs you are taking [1.3.2].
Other NSAIDs and Aspirin
It is generally not recommended to take mefenamic acid with other NSAIDs, whether prescription or over-the-counter [1.5.2]. This includes common pain relievers like ibuprofen (Advil, Motrin) and naproxen (Aleve) [1.5.1]. Combining NSAIDs significantly increases the risk of gastrointestinal side effects such as stomach pain, inflammation, ulcers, and bleeding, without offering greater therapeutic benefit [1.5.2, 1.5.3]. Even low-dose aspirin, often used for cardiovascular protection, should not be taken with mefenamic acid unless specifically advised by a doctor, as the combination heightens the risk of serious GI events [1.2.2].
Alcohol
Consuming alcohol while taking mefenamic acid is strongly discouraged [1.3.4]. Alcohol can irritate the stomach lining, and when combined with an NSAID, it significantly increases the risk of stomach bleeding and ulcers [1.4.1, 1.4.2]. Symptoms of a serious stomach bleed can include bloody or black, tar-like stools, and vomiting blood or material that looks like coffee grounds [1.4.3]. This interaction is considered major, and alcohol should be avoided entirely during treatment [1.4.1].
Anticoagulants (Blood Thinners) and Antiplatelet Drugs
Taking mefenamic acid with anticoagulants like warfarin or antiplatelet drugs such as clopidogrel can dangerously increase the risk of serious bleeding [1.7.1, 1.2.2]. These medications already reduce the blood's ability to clot, and mefenamic acid can enhance this effect [1.7.2]. This synergistic effect means the risk of bleeding when using both drugs is higher than for either drug alone [1.7.2]. Patients on these combinations require careful monitoring for any signs of unusual bleeding or bruising [1.7.1].
Antidepressants (SSRIs and SNRIs)
Selective Serotonin Reuptake Inhibitors (SSRIs) like fluoxetine (Prozac) and sertraline (Zoloft), and Serotonin-Norepinephrine Reuptake Inhibitors (SNRIs) can also increase the risk of bleeding when taken with mefenamic acid [1.8.2, 1.2.2]. These antidepressants can affect platelet function, which is crucial for blood clotting [1.2.2]. Combining them with an NSAID potentiates the risk of gastrointestinal bleeding [1.8.3].
Blood Pressure Medications (ACE Inhibitors, ARBs, Diuretics)
Mefenamic acid can diminish the effectiveness of several types of blood pressure medications, including:
- ACE Inhibitors: such as lisinopril and benazepril [1.3.3].
- Angiotensin Receptor Blockers (ARBs): such as losartan and valsartan [1.12.1].
- Diuretics (Water Pills): such as furosemide and hydrochlorothiazide [1.13.3].
This interaction can lead to uncontrolled high blood pressure [1.12.3]. Furthermore, in elderly patients or those with kidney problems, combining an NSAID with ACE inhibitors or ARBs can lead to a deterioration of renal function [1.2.2].
Lithium and Methotrexate
- Lithium: Used to treat bipolar disorder, lithium levels can be dangerously increased when taken with mefenamic acid. NSAIDs reduce the kidneys' ability to clear lithium from the body, leading to potential toxicity [1.9.2, 1.9.3]. Signs of lithium toxicity include nausea, vomiting, tremors, and confusion [1.9.2].
- Methotrexate: This drug, used for conditions like rheumatoid arthritis and cancer, can also build up to toxic levels when combined with mefenamic acid [1.10.2]. NSAIDs can enhance the toxicity of methotrexate, so caution is required when they are administered concomitantly [1.6.1].
Other Notable Interactions
- Digoxin: Taking mefenamic acid with digoxin, a heart medication, may increase digoxin levels to a harmful point [1.14.1].
- Corticosteroids: Oral corticosteroids like prednisone, when used with mefenamic acid, increase the risk for gastrointestinal bleeding [1.6.1].
- Certain Antacids: Antacids containing magnesium hydroxide (like Milk of Magnesia) can increase the absorption of mefenamic acid, potentially leading to more side effects [1.2.1].
Comparison Table of Mefenamic Acid Interactions
| Interacting Substance/Drug | Potential Risk | Management Advice |
|---|---|---|
| Other NSAIDs (e.g., ibuprofen, naproxen) | Increased risk of GI bleeding and ulcers [1.5.2] | Generally avoid combination [1.5.2]. Consult a doctor for alternatives [1.5.3]. |
| Alcohol | Major increase in risk of stomach bleeding [1.4.1] | Avoid alcohol completely during treatment [1.4.3]. |
| Blood Thinners (e.g., warfarin, apixaban) | Significantly increased risk of serious bleeding [1.7.2] | Doctor may need to adjust dose or prescribe alternatives [1.7.1]. Requires close monitoring. |
| SSRIs/SNRIs (e.g., sertraline, fluoxetine) | Increased risk of GI bleeding [1.8.2] | Use with caution and monitor for bleeding signs [1.8.3]. |
| ACE Inhibitors & ARBs | Reduced blood pressure control, risk of kidney damage [1.2.2, 1.12.1] | Monitor blood pressure and renal function closely [1.12.3]. |
| Diuretics (Water Pills) | Reduced effectiveness of the diuretic, potential kidney issues [1.13.3] | Monitor for signs of renal failure and ensure diuretic efficacy [1.13.3]. |
| Lithium | Increased lithium levels, risk of toxicity [1.9.2] | Requires careful monitoring of lithium levels and for signs of toxicity [1.9.3]. |
| Methotrexate | Increased methotrexate toxicity [1.6.1] | Use with caution; may require dose adjustments and frequent monitoring [1.10.2]. |
Conclusion: Prioritizing Safety
The potential for serious interactions makes it critical to be fully transparent with your healthcare provider about everything you take before starting mefenamic acid. The drug carries a boxed warning from the FDA regarding increased risk of cardiovascular events (like heart attack and stroke) and gastrointestinal bleeding, which can be fatal [1.6.1]. These risks are heightened by improper use and dangerous combinations. Always follow your doctor's instructions, never take more than prescribed, and immediately report any unusual symptoms, such as severe stomach pain, black stools, chest pain, or weakness on one side of the body [1.11.1, 1.11.3].
For more information on NSAID safety, you can visit the FDA's page on Non-Steroidal Anti-Inflammatory Drugs.
