Mefenamic acid
Generic name: mefenamic acid (me fe NAM ik)
Brand name: Ponstel
Dosage forms: oral capsule (250 mg)
Drug class: Nonsteroidal anti-inflammatory drugs
What is mefenamic acid?
Mefenamic acid is a non-selective COX-1 and COX-2 inhibitor that is used to relieve pain, inflammation, and fever.
Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that is used short-term (7 days or less) to treat mild to moderate pain in adults and children who are at least 14 years old. Mefenamic acid is also used to treat menstrual pain.
Mefenamic acid may also be used for purposes not listed in this medication guide.
Warnings
Mefenamic acid can increase your risk of fatal heart attack or stroke. Do not use mefenamic acid just before or after heart bypass surgery (coronary artery bypass graft, or CABG). Mefenamic acid may also cause stomach or intestinal bleeding, which can be fatal.
Mefenamic acid Uses:
Pain, mild to moderate:
- It acts as a pain killer in patients more than 14 years of age, when therapy will not exceed 1 week.
Primary dysmenorrhea:
- It is also indicated in the treatment of primary dysmenorrhea.
Note: Use the lowest effective dose for the shortest possible duration.
Mefenamic acid Dose in the treatment of Pain, mild to moderate:
- Oral: Initial: 500 mg, then 250 mg every 6 hours as needed; usually not more than 1 week.
Mefenamic acid Dose in the treatment of Primary dysmenorrhea:
- Oral: Initial: 500 mg beginning at the onset of bleeding and associated symptoms, followed by 250 mg every 6 hours (manufacturer’s labeling) or 500 mg 3 times daily (Delgado 1994; De Mello 2004; Langrick 1989); usually no more than 3 days.
Use in Children:
Not indicated.
Mefenamic acid Pregnancy Risk Category: C (D in the third trimester)
- It can also cross the placental boundary.
- Some studies have shown that birth defects can be caused by in utero NSAID use. However, the data is inconsistent.
- In utero NSAIDs have been shown to cause nonteratogenic effects in the fetus/neonate, such as prenatal constriction and persistent pulmonary hypertension, oligohydramnios and necrotizing enterocolitis.
- Additionally, postnatal non-closure of ductus arteriosus may occur. This can be difficult to manage medically.
- Avoid using NSAIDs during pregnancy. They can cause premature closure of ductus arteriosus.
- The long-term use of it can cause infertility in women of childbearing years. However, this can be reversed by stopping the therapy.
- It should be avoided by women who are having trouble conceiving and those who are undergoing fertility treatment.
- The product of conception may experience miscarriage if NSAIDs are used close to the time of conception.
Mefenamic acid use during breastfeeding:
- Breast milk may contain mefenamic acid.
- Based on the highest concentration of breast milk, the relative infant dose (RID), of mefenamic acids is 0.92%. This is when it’s compared to a maternal weight-adjusted dose of 750mg/day.
- RID 10% is generally acceptable for breastfeeding, while RID 25% should be avoided.
- The highest possible milk concentration (0.66 mg/mL) is used to calculate the daily infant dose via breastmilk at 0.099 mg/kg/day.
- The milk concentration was determined after maternal administration of oral mefenamic Acid 500 mg and 250 mg three times per day. Samples were taken on days 2 through 4.
- We can detect mefenamic acids in the urine and serum of breastfeeding infants.
- NSAIDs can be used by postpartum mothers who want to breastfeed. However, other agents than mefenamic acids are preferable (Montgomery 2012). Breastfeeding infants with platelet dysfunction and thrombocytopenia should not be allowed to use NSAIDs.
- The manufacturer suggests that the mother decide whether to stop breastfeeding or discontinue using the drug. This is in consideration of the possibility of serious adverse reactions in breastfeeding infants.
Ponstan Dose in patients with kidney disease:
- Avoid use in patients with preexisting renal disease and in patients with advanced renal disease.
KDIGO 2012 guidelines provide the following recommendations for NSAIDs:
- eGFR 30 to <60 mL/minute/1.73 m²:
- Temporarily discontinue in patients with intercurrent disease that increases the risk of acute kidney injury.
- eGFR <30 mL/minute/1.73 m²:
- Avoid use.
- eGFR 30 to <60 mL/minute/1.73 m²:
Ponstan Dose in patients with Liver disease:
There are no dosage adjustments provided in the manufacturer’s labeling (has not been studied); however, an adjustment may be necessary due to extensive hepatic metabolism.
Side Effects of Mefenamic acid (Ponstan):
Central nervous system:
- Dizziness
- Headache
- Nervousness
Dermatologic:
- Pruritus
- Skin rash
Endocrine & metabolic:
- Fluid retention
Gastrointestinal:
- Abdominal cramps
- Abdominal distress
- Abdominal pain
- Constipation, diarrhea
- Duodenal ulcer (with bleeding or perforation)
- Dyspepsia
- Flatulence
- Gastric ulcer (with bleeding or perforation)
- Gastritis
- Heartburn
- Nausea
- Vomiting
Hematologic & oncologic:
- Hemorrhage
Hepatic:
- may increase liver enzymes
Otic:
- Tinnitus
Contraindications to Mefenamic acid (Ponstan):
- If you have hypersensitivity to mefenamic or any other component of the formulation, Mefenamic Acid is contraindicated
- It is not recommended for use in the treatment of coronary bypass graft surgery (CABG).
- Patients who have had a history of asthma, urticaria or allergic-type reactions to aspirin or any other NSAIDs.
Canadian labeling: Additional contraindications (not in US labeling).
- Pregnancy in the third trimester
- Breast-feeding
- Grave uncontrolled heart disease;
- Active gastric, duodenal or peptic ulcer
- active gastrointestinal bleeding;
- cerebrovascular bleeding and other bleeding disorders
- Inflammatory bowel disease
- severe hepatic impairment, active hepatic diseases
- Grave renal impairment (CrCl 30 mg/minute) or deteriorating kidney disease
- Hyperkalemia is a known condition.
- Adolescents 18 and under
Warnings and precautions
Anaphylactoid reactions
- Anaphylactoid reactions can occur even in patients who have never been exposed to anaphylactic substances.
- Patients with the “aspirin trifecta” (bronchial asthma and aspirin intolerance, rhinitis) could be at higher risk.
- Contraindicated in patients with bronchospasm, asthma, rhinitis, or urticaria with NSAID or aspirin therapy.
Cardiovascular events: [US Boxed Warn]
- NSAIDs can increase the risk of severe (and possibly fatal) adverse cardiovascular thrombotic conditions, such as stroke and myocardial damage.
- This risk can occur during treatment, and it may increase as the use continues.
- The relative risk seems to be the same in people with and without cardiovascular disease, or risk factors for it. However, absolute cardiovascular thrombotic events may occur earlier in treatment in those who have known cardiovascular disease and those who are at higher risk.
- Exacerbation or new-onset hypertension can occur. NSAIDs could also impair the response to ACE inhibitors, thiazide or loop diuretics; may lead to cardiovascular events.
- It may cause fluid retention and sodium buildup; take extra care with edematic patients.
- Do not give to patients with heart failure.
- If there are any cardiovascular thrombotic risks, do not give this medication to patients who have had a recent myocardial injury.
- To reduce your risk of developing cardiovascular events, use the lowest effective dose for the shortest time. This is consistent with the individual patient’s goals.
- Alternate therapy is recommended for high-risk patients.
CNS effects
- This may cause blurred vision, drowsiness, or dizziness.
- Encourage patients to pay attention when performing tasks that require mental alertness (eg driving or operating machinery)
GI events: [US Boxed Warning]
- NSAIDs increase the risk of severe GI inflammation, ulceration and bleeding (may be fatal); patients older than 65 years old and those with a history peptic ulcer disease or GI bleeding are more at risk.
- These events can occur without warning and at any time during therapy.
- It should be avoided when there is active bleeding.
- Avoid non-aspirin, non-steroidal anti-inflammatory drugs (NSAIDs) for patients who have had a history or experience of severe lower gastrointestinal bleeding.
- Use caution with a history of gastrointestinal ulcers, concurrent therapy known to increase the risk of GI bleeding (eg, aspirin, anticoagulants and/or corticosteroids, selective serotonin reuptake inhibitors), advanced hepatic disease, coagulopathy, smoking, use of alcohol, or in the elderly or debilitated patients.
- To reduce the chance of complications, use the lowest effective dose for the most time. This is consistent with the individual patient’s goals. Alternate therapies should be considered in high-risk patients.
- Concomitant use of aspirin can lead to a significant increase in the risk for gastrointestinal complications (eg ulcers). Therefore, concomitant gastroprotective treatment (eg proton pump inhibitors), is highly recommended (Bhatt, 2008).
Hematologic effects
- The functions of platelets such as adhesion or aggregation can be reduced; bleeding time may increase; patients with coagulation problems or those who are on anticoagulants need to be closely monitored.
- Anemia can occur. Patients on long-term NSAID therapy need to be closely monitored.
- Rarely, NSAIDs have been linked to severe blood dyscrasias, such as thrombocytopenia, agranulocytosis and aplastic anemia.
Hepatic effects
- Transaminase levels rise with its use; closely monitor patients who have abnormal LFT.
- Rare but sometimes fatal hepatic reactions have been linked to NSAIDs.
- If you notice any signs or symptoms of hepatic diseases, or if there are systemic manifestations, stop taking the medication immediately.
Hyperkalemia:
- NSAIDs can increase hyperkalemia risk, especially in elderly people, diabetics, and those who use concomitantly with other agents that induce hyperkalemia (eg ACE-inhibitors).
- Hyperkalemia can have fatal consequences, so it is important to monitor potassium levels.
Effects on the renal system:
- NSAIDs can affect renal function. Dose-dependent decreases of prostaglandin synthesis could be caused by NSAIDs. This may reduce renal blood flow, which can cause renal decompensation (usually reversible).
- Patients with impaired renal function, dehydration and hypovolemia, heart disease, hepatic impairment, diuretics, ACE inhibitors, or the elderly are at greater risk for renal toxicity.
- Before you start therapy, ensure that the patient has enough water. Also, be sure to monitor your renal function.
- Long-term NSAID abuse can cause renal injury that could lead to renal papillary necrosis.
Reactions to skin:
- NSAIDs can have severe dermatologic effects and may lead to potentially fatal skin adverse reactions, including Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis, and exfoliative dermatitis (TEN). These events may not be a warning sign.
- Stop using the product immediately you notice a skin rash or other signs of hypersensitivity.
Asthma
- Patients with asthma that is aspirin-sensitive should not use this product. Bronchospasm can be severe and possibly fatal.
- Take extra care when treating other types of asthmatic patients.
Coronary bypass surgery for coronary artery bypass: [US Boxed Warn]
- In the case of coronary bypass graft (CABG), surgery, it is not recommended to use.
- Following CABG surgery, the risk of stroke and myocardial damage may increase.
Hepatic impairment
- Patients with impaired liver function should be cautious; dosage adjustments may need to be made due to a high level of hepatic metabolism.
- Patients suffering from advanced hepatic diseases are more at risk for gastrointestinal bleeding when they take NSAIDs.
Renal impairment
- Patients with pre-existing renal disease or advanced renal disease should not be given this medication. If therapy is necessary, it is important to monitor the renal function.
Monitoring parameters:
- CBC,
- chemistry profile,
- occult blood loss,
- periodic liver function tests;
- renal function (urine output, serum BUN and creatinine);
- signs or symptoms of gastrointestinal bleeding;
- blood pressure.
How to administer Mefenamic acid ?
Administer with food, milk, or antacids.
Mechanism of action of Mefenamic acid :
It reverses the inhibition of cyclooxygenase-1 (COX-1) enzymes. This results in decreased production of prostaglandin precursors.
It is an antipyretic, analgesic and anti-inflammatory agent.
Other proposed mechanisms not fully elucidated (and possibly contributing to the anti-inflammatory effect to varying degrees) include inhibiting chemotaxis, altering lymphocyte activity, inhibiting neutrophil aggregation/activation, and decreasing proinflammatory cytokine levels.
Absorption:
- Rapidly absorbed
Protein binding:
- >90% to albumin
Metabolism:
- Hepatic via CYP2C9 to metabolites (activity not known)
Half-life elimination:
- About 2 hours
Time to peak:
- 2 to 4 hours
Excretion:
- Urine (~52%) and feces (~20%) as unchanged drug and metabolites
International Brand Names of Mefenamic acid:
- Ponstel
- DOM-Mefenamic Acid
- PMS-Mefenamic Acid
- Ponstan
- Afloxan
- Alfoxan
- Alfoxid
- Algex
- Algifort
- Allogon
- Amifen
- Analspec
- Asmef
- Atmose
- Beafemic
- Betamef
- Coly
- Conamic
- Coslan
- Datan Forte
- Dolor
- Dolostan
- Dysmen
- Ecopan
- Fenagesic
- Fenam
- Fenamic
- Fenamin
- Fenamol
- Fendol
- Fendol DS
- Gandin
- Gandin DS
- Gardan
- Hispen
- Hostan
- Inflasic
- Johnstal
- Konafen
- Lysalgo
- Manic
- Manomic
- Mecid A
- Mefac
- Mefacit
- Mefcid
- Mefen
- Mefenamynka
- Mefepain
- Mefex
- Nam
- Namic
- Napan
- Nichostan
- Painnox
- Painstop
- Parkemed
- Passton
- Pehastan
- Poncofen
- Pondex
- Pondnadysmen
- Ponmel
- Pono
- Ponser
- Ponstan
- Ponstan Forte
- Ponstan-500
- Ponstil
- Ponstyl
- Pontacid
- Pontal
- Pontalon
- Potarlon
- Ralgec
- Sefmic
- Shanamef
- Sicadol
- Solasic
- Spegic Forte
- Tanston
- Varistan
- Vidan
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