Mefenamic Acid for Seniors: Safety, Dosage & Guidelines

When treating pain in older adults, Mefenamic acid is a non‑steroidal anti‑inflammatory drug (NSAID) commonly prescribed for mild to moderate musculoskeletal pain and dysmenorrhea. It belongs to the anthranilic‑acid class of NSAIDs and works by inhibiting cyclooxygenase enzymes, reducing prostaglandin production. Because the elderly often have multiple health issues, understanding mefenamic acid safety is essential before adding it to a medication regimen.

Safety Concerns for Seniors

Older patients face a higher risk of gastrointestinal (GI) bleeding, renal impairment, and cardiovascular events when taking NSAIDs. Mefenamic acid is no exception. The drug can irritate the stomach lining, leading to ulcers or bleeding, especially in those with a history of peptic ulcer disease or who use anticoagulants. Renal function declines with age, and NSAIDs can further reduce blood flow to the kidneys, potentially precipitating acute kidney injury. Cardiovascular risk-such as increased blood pressure and heart‑failure exacerbation-must also be weighed.

Pharmacokinetics and Aging

Age‑related changes affect how the body absorbs, distributes, metabolizes, and excretes mefenamic acid. The drug’s half‑life (about 2 hours in young adults) can extend to 3‑4 hours in seniors due to slower hepatic metabolism and reduced renal clearance. Plasma protein binding may be altered by lower albumin levels, increasing the free drug fraction and the chance of side effects. These pharmacokinetic shifts mean that the same dose that’s safe for a 35‑year‑old could be excessive for an 80‑year‑old.

Recommended Dosage in Elderly Patients

Guidelines suggest a lower initial dose and a shorter treatment duration for older adults:

• Initial dose: 250 mg orally every 6 hours.
• Maximum daily dose: 750 mg (i.e., three 250 mg doses) for a maximum of 5 days.
• If pain persists, consider alternating with acetaminophen rather than increasing the dose.

For patients with mild to moderate renal impairment (creatinine clearance 30‑50 mL/min), the dose should be reduced to 125 mg every 8 hours, not exceeding 375 mg per day. Those with severe renal failure should avoid mefenamic acid altogether.

Contraindications & When to Avoid

Mefenamic acid should be withheld in the following situations:

1. Known hypersensitivity to anthranilic‑acid NSAIDs.
2. Active or recent (< 3 months) GI ulcer or bleeding.
3. Severe heart failure (NYHA class III‑IV) or uncontrolled hypertension.
4. Advanced chronic kidney disease (eGFR < 30 mL/min/1.73 m²).
5. Concurrent use of anticoagulants such as warfarin without close INR monitoring.

Pregnant women (especially in the third trimester) and patients with asthma exacerbated by NSAIDs should also avoid it.

Managing Common Side Effects

When side effects arise, a step‑wise approach can help:

• Stomach upset: Take the medication with food or a full glass of milk; consider a proton‑pump inhibitor (omeprazole 20 mg daily) for protection.
• Headache or dizziness: Verify hydration status and assess for hypotension.
• Kidney‑related symptoms: Monitor serum creatinine and urine output; discontinue if creatinine rises > 0.3 mg/dL within 48 hours.

Educate patients and caregivers to report any new bruising, dark stools, or sudden swelling promptly.

Drug Interactions Important for Older Adults

Polypharmacy is common in seniors, making interaction checks vital. Notable interactions include:

• Anticoagulants (warfarin, dabigatran): Heightened bleeding risk; monitor INR or thrombin time.
• Other NSAIDs (ibuprofen, naproxen): Additive GI and renal toxicity; avoid concurrent use.
• ACE inhibitors or ARBs: Reduced renal perfusion; monitor blood pressure and kidney function.
• Selective serotonin reuptake inhibitors (SSRIs): Increased bleeding risk.
• Diuretics: Potential for electrolyte imbalance and worsening renal function.

Always review the full medication list before prescribing.

Comparison with Other NSAIDs Commonly Used in Seniors

From the table, naproxen shows the lowest GI and renal risk, while diclofenac carries the highest cardiovascular danger. Mefenamic acid sits in the middle, making it a reasonable option when short‑term use is needed and other agents are unsuitable.

Practical Recommendations for Clinicians & Caregivers

To use mefenamic acid safely in older adults, follow these steps:

1. Conduct a thorough medication review, focusing on anticoagulants, other NSAIDs, and antihypertensives.
2. Assess baseline renal function (eGFR) and GI history.
3. Start with the lowest effective dose (250 mg q6h) and limit therapy to 5 days.
4. Prescribe gastro‑protective agents if the patient has a prior ulcer or is on low‑dose aspirin.
5. Schedule follow‑up labs (creatinine, electrolytes) after 48‑72 hours, especially if the patient has comorbid kidney disease.
6. Educate the patient and caregiver on warning signs: black stools, sudden swelling, or dizziness.
7. If pain persists beyond 5 days, switch to acetaminophen or consider physical therapy before restarting NSAIDs.

Documenting these measures in the medical record helps ensure continuity of care across providers.

Frequently Asked Questions