Mefenamic acid

Common Uses

Mefenamic acid is primarily prescribed for the following conditions:

• Mild to moderate pain: It is used to manage short-term pain resulting from various conditions in adults and adolescents.
• Menstrual cramps: It is frequently used to treat pain associated with menstrual periods, also known as primary dysmenorrhea.

Usage Guidelines

This medication is intended for short-term use. Healthcare providers typically prescribe it for no longer than seven days at a time for general pain relief, or for the first few days of a menstrual period. It is approved for use in adults and children who are at least 14 years of age.

How Mefenamic Acid Works

Mefenamic acid belongs to a group of medicines called nonsteroidal anti-inflammatory drugs, or NSAIDs. It works by blocking the action of enzymes in the body called cyclooxygenase (COX). These enzymes are responsible for producing prostaglandins, which are hormone-like chemicals that signal pain and cause inflammation and fever.

When the production of prostaglandins is reduced, the body experiences less pain and swelling. This mechanism is effective for several conditions:

• Pain Relief: By lowering prostaglandin levels, the medication reduces the intensity of pain signals sent to the brain.
• Menstrual Cramps: It helps relieve menstrual pain by lowering the level of prostaglandins in the lining of the uterus, which reduces the strength of uterine contractions.
• Inflammation: It decreases the swelling and redness associated with inflammatory responses in the body.

Mefenamic acid is typically used for short-term relief because it targets the immediate chemical signals of pain and inflammation rather than treating an underlying chronic condition.

Common Side Effects

Many people using mefenamic acid experience mild side effects. These may include:

• Stomach pain, gas, or bloating
• Nausea and vomiting
• Heartburn
• Diarrhea or constipation
• Dizziness or headache
• Ringing in the ears

Serious Side Effects

Stop using this medication and contact a healthcare provider immediately if you experience any of the following serious symptoms:

Allergic and Skin Reactions

• Signs of an allergic reaction, such as hives, swelling of the face or throat, or difficulty breathing
• A severe skin rash that is red or purple and includes blistering or peeling

Cardiovascular and Neurological Issues

• Chest pain spreading to the jaw or shoulder
• Sudden numbness or weakness, especially on one side of the body
• Slurred speech or vision changes
• Shortness of breath

Gastrointestinal and Internal Organ Issues

• Signs of stomach bleeding, such as black, bloody, or tarry stools, or coughing up blood or vomit that looks like coffee grounds
• Liver problems, including yellowing of the skin or eyes (jaundice), dark urine, or pain in the upper right stomach
• Kidney problems, such as little or no urination or swelling in the feet and ankles
• Anemia symptoms, including pale skin and feeling unusually tired or light-headed

Boxed Warning: Cardiovascular and Gastrointestinal Risks

Mefenamic acid may increase the risk of serious cardiovascular thrombotic events, including heart attack and stroke, which can be fatal. This risk may increase with longer duration of use. It is contraindicated for the treatment of peri-operative pain in the setting of coronary artery bypass graft (CABG) surgery.

Nonsteroidal anti-inflammatory drugs (NSAIDs), including mefenamic acid, cause an increased risk of serious gastrointestinal (GI) adverse events including bleeding, ulceration, and perforation of the stomach or intestines. These events can occur at any time during use and without warning symptoms. Elderly patients are at greater risk for serious GI events.

Contraindications

• Known hypersensitivity to mefenamic acid.
• History of asthma, hives, or allergic-type reactions after taking aspirin or other NSAIDs.
• Treatment of pain before or after heart bypass surgery.
• Active ulceration or chronic inflammation of either the upper or lower gastrointestinal tract.
• Pre-existing renal disease.

Other Precautions

Kidney and Liver Health: Long-term use of NSAIDs has resulted in kidney injury. Patients with pre-existing kidney disease, heart failure, or liver dysfunction, and those taking diuretics or ACE inhibitors, are at higher risk. Liver function should be monitored, as rare but severe hepatic reactions can occur.

Skin Reactions: Serious skin reactions such as exfoliative dermatitis, Stevens-Johnson Syndrome (SJS), and toxic epidermal necrolysis (TEN) can occur without warning. Use should be discontinued at the first appearance of a skin rash or any other sign of hypersensitivity.

Pregnancy: Use of mefenamic acid should be avoided starting at 20 weeks of pregnancy as it may cause rare but serious kidney problems in the unborn baby. It must be avoided starting at 30 weeks of pregnancy due to the risk of premature closure of the fetal ductus arteriosus.

Anemia: Anemia is sometimes seen in patients receiving NSAIDs. Patients on long-term treatment should have their hemoglobin or hematocrit checked if they exhibit signs of anemia.

Pregnancy

Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID). Use of this medication during pregnancy can lead to complications for the developing fetus, particularly in the second and third trimesters:

• At 20 weeks or later: Taking NSAIDs may cause rare but serious kidney problems in the unborn baby. This can result in low levels of amniotic fluid, the liquid that surrounds and protects the fetus.
• At 30 weeks or later: Use should be avoided because it may cause the premature closure of a vital blood vessel in the baby's heart (the ductus arteriosus), which can lead to serious heart or lung issues after birth.

Mefenamic acid may also temporarily reduce fertility in women, making it more difficult to conceive while taking the medication. If you are pregnant or planning to become pregnant, consult a healthcare professional to discuss the risks and benefits of this treatment.

Breastfeeding

Small amounts of mefenamic acid can pass into breast milk. Because the potential effects on a nursing infant are not fully established, it is important to talk to a healthcare provider before using this medication while breastfeeding. They can help determine if the benefits of the medication outweigh the potential risks to the baby.

Available Forms

Mefenamic acid is provided for oral administration in the following form:

• Capsule

This medication is taken by mouth. It is generally recommended to take the capsule with food or milk to reduce the risk of stomach upset.

FDA Approval and Indications

Mefenamic acid is FDA-approved for the short-term treatment of mild to moderate pain in adults and children at least 14 years of age. It is also approved for the treatment of primary dysmenorrhea (menstrual cramps). The FDA labeling specifies that the duration of treatment should generally not exceed seven days.

Boxed Warning

Mefenamic acid carries a boxed warning, which is the most serious warning required by the FDA. This warning highlights the following risks associated with nonsteroidal anti-inflammatory drugs (NSAIDs):

• Cardiovascular Risk: NSAIDs may increase the risk of serious cardiovascular thrombotic events, such as heart attack and stroke, which can be fatal. This risk can occur early in treatment and may increase with the length of use.
• Gastrointestinal Risk: NSAIDs increase the risk of serious gastrointestinal (GI) events, including bleeding, ulceration, and perforation of the stomach or intestines, which can be fatal. These events can occur at any time during use and without warning symptoms.

Safety Communications

The FDA has issued safety communications to strengthen warnings for all non-aspirin NSAIDs regarding the risk of heart attack and stroke. These communications emphasize that the risk is present even in patients without heart disease or risk factors, although those with heart disease are at higher risk. Mefenamic acid is available by prescription only.

Risks During Pregnancy

Mefenamic acid should generally be avoided during pregnancy, particularly in the second and third trimesters, due to potential risks to the developing fetus.

• Kidney and Amniotic Fluid Issues: Starting around 20 weeks of pregnancy, taking mefenamic acid may cause the baby to develop kidney problems. This can lead to low levels of amniotic fluid, which is the protective liquid surrounding the fetus.
• Heart Complications: Taking this medication at 30 weeks of pregnancy or later is strongly discouraged. It can cause the premature closure of the ductus arteriosus, a blood vessel in the baby's heart. This can lead to serious heart or lung issues in the newborn.

Labor and Delivery

Using mefenamic acid late in pregnancy may also interfere with labor and delivery. It may delay the onset of labor or increase the risk of bleeding for both the mother and the baby.

Medical Consultation

If you are pregnant, suspect you might be pregnant, or are planning to become pregnant, consult your healthcare provider before using mefenamic acid. They can help evaluate the risks and recommend safer alternatives for managing pain or inflammation during pregnancy.