Mefenamic acid oral
- Drugs List
- Therapeutic Indications
- Dosage
- Contraindications
- Precautions and Warnings
- Pregnancy and Lactation
- Side Effects
- Monograph
Presentation
Oral formulations of mefenamic acid
Drugs List
Therapeutic Indications
Uses
Dysmenorrhoea
Menorrhagia
Osteoarthritis
Pain - mild to moderate
Pyrexia in children
Relief of headache
Rheumatoid arthritis
Still's disease (juvenile arthritis)
Anti-inflammatory analgesic for the symptomatic relief of:
Rheumatoid arthritis (including Still's disease);
Osteoarthritis;
Pain including muscular, traumatic, dental, postoperative and post-partum;
Headache.
Primary dysmenorrhoea.
Pyrexia in children.
Menorrhagia due to dysfunction and presence of an IUD when other pelvic pathology has been ruled out.
Dosage
Adults
The recommended dose is 500 mg three times daily.
In menorrhagia to be administered on the first day of excessive bleeding and continued according to the judgement of the physician.
In dysmenorrhoea to be administered at the onset of menstrual pain and continued according to the judgement of the physician.
Elderly
The recommended dose is 500 mg three times daily.
The elderly are at increased risk of the serious consequences of adverse reactions.
Children
Infants over 6 months to children 12 years
Mefenamic acid suspension 50 mg/5 ml is licensed in infants over 6 months.
Infants over 6 months 25 mg/kg of bodyweight daily in divided doses or:
The following doses can be used in specific age ranges:
9 years to 12 years: four 5 ml spoonfuls.
5 years to under 9 years: three 5 ml spoonfuls
2 years to under 5 years: two 5 ml spoonfuls
6 months to under 2 years: one 5 ml spoonfuls
Doses may be repeated as necessary, up to three times daily.
Apart from the treatment of Still's disease, therapy should not be continued for longer than 7 days.
Children aged 12 to 18 years
The recommended dose is 500 mg three times daily.
In menorrhagia to be administered on the first day of excessive bleeding and continued according to the judgement of the physician.
In dysmenorrhoea to be administered at the onset of menstrual pain and continued according to the judgement of the physician.
Patients with Renal Impairment
Use the lowest effective dose and monitor closely.
Additional Dosage Information
Recommended dose should not be exceeded. Overdose has been reported in daily doses of less than 3 g.
Contraindications
Children under 6 months
Coronary artery bypass graft
Breastfeeding
Galactosaemia
Gastrointestinal haemorrhage
Gastrointestinal ulcer
History of gastrointestinal haemorrhage
History of gastrointestinal perforation
History of gastrointestinal ulceration
History of peptic ulcer
Inflammatory bowel disease
Peptic ulcer
Severe cardiac failure
Severe hepatic impairment
Severe renal impairment
Third trimester of pregnancy
Precautions and Warnings
Elderly
Haemorrhagic diathesis
Risk factors for cardiovascular disorder
Asthma
Cardiac failure
Cardiac impairment
Cerebrovascular disorder
Connective tissue disorder
Crohn's disease
Dehydration
Diabetes mellitus
Epileptic disorder
First trimester of pregnancy
Glucose-galactose malabsorption syndrome
Hepatic impairment
History of asthma
Hypertension
Intracranial haemorrhage
Ischaemic heart disease
Lactose intolerance
Peripheral arterial circulatory disorder
Porphyria
Renal impairment
Respiratory impairment
Second trimester of pregnancy
Systemic lupus erythematosus
Ulcerative colitis
NSAIDs may provoke or exacerbate asthma
Advise ability to drive/operate machinery may be affected by side effects
Not all formulations are suitable for use in children under 12 years
Not all presentations are licensed for all indications
Some formulations contain lactose
Discontinue if signs of gastro-intestinal bleeding occur
Monitor liver function on prolonged therapy
Monitor renal function in patients with cardiac impairment
Monitor renal function in patients with hepatic impairment
Monitor renal function in patients with renal impairment
Perform blood counts on prolonged use of this treatment
Excessive use may increase frequency of headache, may require withdrawal
NSAIDs may provoke bronchospasm/urticaria in susceptible patients
Risk of gastro-intestinal bleeding increased in the elderly
Severe gastro-intestinal side effects may occur without warning
Discontinue if blood dyscrasia develops
Discontinue if diarrhoea or skin rash occurs
Discontinue if liver function disturbance occurs
Maintain treatment at the lowest effective dose
Maintain treatment for the shortest possible duration
Female: Reduced fertility (reversible) possible with long term use
Non-oliguric renal failure and proctocolitis have been reported mainly in elderly patients who have not discontinued mefenamic acid after the development of diarrhoea. The elderly have an increased frequency of adverse reactions to NSAIDs especially gastrointestinal bleeding and perforation which may be fatal. Monitor regularly for gastrointestinal bleeding.
Serious skin reactions, some fatal, including exfoliative dermatitis, Stevens-Johnson syndrome, and toxic epidermal necrolysis, have been reported with the administration of NSAIDs. Most symptoms occur early in the course of treatment, the majority of which appear within the first few months. Mefenamic acid should be discontinued if skin rash, mucosal lesions or other signs of hypersensitivity occur.
The use of some NSAIDs (particularly at high doses and in long term treatment) may be associated with a small increased risk of arterial thrombotic events (for example myocardial infarction or stroke).
Care should be taken when administering mefenamic acid to patients suffering from intracranial haemorrhage and bleeding diathesis. This is due to the possibility of interference with platelet function.
Pregnancy and Lactation
Pregnancy
Mefenamic acid is contraindicated in the third trimester of pregnancy.
Until recently, first trimester exposure to NSAIDs was not associated with an increased risk of birth defects. There has since been conflicting evidence from registry based studies regarding the risk of cardiac septal defects, although risks were not confirmed in later studies and when re-evaluating the original data. Animal studies have shown reproductive toxicity (Schaefer, 2007).
Mefenamic acid is a prostaglandin synthetase inhibitor and may have the following effects during the 2nd and 3rd trimesters:
- Pulmonary and cardiac toxicity in the foetus (pulmonary hypertension with preterm closing of the ductus
arteriosus). The risk exists from the beginning of the 6th month and increases if administration is close to full term.
- Functional renal injury in the foetus. From the 12th week: oligohydramnios (usually reversible after the end of treatment) or anamnios (particularly with prolonged exposure). Following birth, renal failure may persist (especially with late and prolonged exposure).
- Inhibition of uterine contractions with delayed onset and prolongation of labour.
- Increased possibility of bleeding in mother and child.
- Increased risk of oedema formation in the mother. (Schaefer, 2007).
NSAIDs may reduce ovulation and therefore fertility and have been associated with an increased rate of miscarriage, though this is debated (Schaefer, 2007).
Congenital abnormalities have been reported in association with NSAID administration in man; however these are low in frequency and do not appear to follow any discernible pattern. NSAIDs should not be used in the first two trimesters of pregnancy unless clearly essential.
When an NSAID is considered essential in the first and second trimester, a more established drug such as ibuprofen may be considered. Schaefer concludes that use of a non-preferred agent in early pregnancy (such as mefenamic acid) does not require termination of pregnancy or invasive diagnostic procedures (Schaefer, 2007).
Several adverse effects have been reported when very pre-term and very low birth weight infants have been exposed to NSAIDs including necrotising enterocolitis and intraventricular haemorrhages (Schaefer, 2007).
The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Lactation
Mefenamic acid is contraindicated in breastfeeding.
In limited studies so far available, NSAIDs can appear in breast milk in very low concentrations.
When an NSAID is considered necessary during breast feeding ibuprofen would be the drugs of choice (Schaefer, 2007).
Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
Specialist advice is available from the UK Drugs in Lactation Advisory Service at https://www.midlandsmedicines.nhs.uk/content.asp?section=6&subsection=17&pageIdx=1
Side Effects
Abnormal liver function tests
Aggravation of existing asthma
Agranulocytosis
Allergic reaction
Anaemia
Anaphylaxis
Angioedema
Anorexia
Aplastic anaemia
Arterial thrombosis
Aseptic meningitis
Asthma
Bone marrow hypoplasia
Bronchospasm
Bullous dermatoses
Cardiac failure
Cholestatic jaundice
Colitis
Confusion
Convulsions
Decrease in haematocrit
Dehydration
Depression
Diarrhoea
Disorientation
Dizziness
Drowsiness
Dyspepsia
Dyspnoea
Ear pain
Enterocolitis
Eosinophilia
Erythema multiforme
Exacerbation of colitis
Exacerbation of Crohn's disease
Exfoliative dermatitis
Facial oedema
False positive test for bile in urine
Fatigue
Fever
Gastro-intestinal perforation
Gastro-intestinal ulceration and bleeding
Glomerulonephritis
Haematemesis
Haematuria
Haemolytic anaemia
Hallucinations
Headache
Hepatitis
Hepato-renal syndrome
Hepatotoxicity
Hypersensitivity reactions
Hypertension
Hyponatraemia
Hypotension
Increased susceptibility to infection
Insomnia
Interstitial fibrosis
Interstitial nephritis
Intravascular coagulation (disseminated)
Laryngeal oedema
Leukopenia
Lyell's syndrome
Malaise
Melaena
Multiorgan failure
Nephrotic syndrome
Nervousness
Neutropenia
Non-oliguric renal failure
Oedema
Optic neuritis
Palpitations
Pancreatitis
Pancytopenia
Papillary necrosis
Perspiration
Proctocolitis
Proteinuria
Pyrexia
Renal failure
Renal impairment
Sepsis
Skin reactions
Steatorrhoea
Stevens-Johnson syndrome
Thrombocytopenia
Thrombocytopenic purpura
Toxic epidermal necrolysis
Ulcerative stomatitis
Vertigo
Overdosage
It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.
The following number will direct the caller to the relevant local centre (0844) 892 0111
Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( www.toxbase.org ) or if this is unavailable at the backup site ( www.toxbasebackup.org ).
Further Information
Last Full Review Date: January 2016
Reference Sources
Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.
Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.
Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press Accessed on 18 January 2016.
Paediatric Formulary Committee. BNF for Children (online) London: BMJ Group, Pharmaceutical Press, and RCPCH Publications Accessed on 18 January 2016.
Summary of Product Characteristics: Mefenamic acid 250mg capsules. Amdipharm Mercury Company Ltd. Revised September 2012.
Summary of Product Characteristics: Mefenamic acid suspension 50mg/5ml. Chemidex Pharma Ltd. Revised January 2016.
Summary of Product Characteristics: Ponstan capsules 250mg. Chemidex Pharma Ltd. Revised December 2015.
Summary of Product Characteristics: Ponstan forte tablets 500mg. Chemidex Pharma Ltd. Revised July 2015.
US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
Available at: https://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT
Mefenamic acid Last revised: 10 March, 2015
Last accessed: 18 January, 2016
The drug database for acute porphyria (NAPOS)
Available at: https://www.drugs-porphyria.org/languages/UnitedKingdom/s1.php?l=gbr
Mefenamic acid Last revised: 16 April, 2010
Last accessed: 18 January, 2016
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