Meclofenamic acid (used as meclofenamate sodium, brand name Meclomen) is a drug used for joint, muscular pain, arthritis and

dysmenorrhea Dysmenorrhea, also known as period pain, painful periods or menstrual cramps, is pain during menstruation. Its usual onset occurs around the time that menstruation begins. Symptoms typically last less than three days. The pain is usually in the ...

. It is a member of the anthranilic acid derivatives (or fenamate) class of

nonsteroidal anti-inflammatory drugs Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

(NSAIDs) and was approved by the US FDA in 1980. Like other members of the class, it is a

cyclooxygenase Cyclooxygenase (COX), officially known as prostaglandin-endoperoxide synthase (PTGS), is an enzyme (specifically, a family of isozymes, ) that is responsible for formation of prostanoids, including thromboxane and prostaglandins such as prost ...

(COX) inhibitor, preventing the formation of

prostaglandins The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are deri ...

. Scientists led by Claude Winder from Parke-Davis invented meclofenamate sodium in 1964, along with fellow members of the class,

mefenamic acid Mefenamic acid is a member of the anthranilic acid derivatives (or fenamate) class of nonsteroidal anti-inflammatory drugs (NSAIDs), and is used to treat mild to moderate pain. Its name derives from its systematic name, dimethylphenylaminobenz ...

in 1961 and

flufenamic acid Flufenamic acid (FFA) is a member of the anthranilic acid derivatives (or fenamate) class of nonsteroidal anti-inflammatory drugs (NSAIDs). Like other members of the class, it is a cyclooxygenase (COX) inhibitor, preventing the formation of pr ...

in 1963. Patents on the drug expired in 1985 and several generics were introduced in the US, but as of July 2015 only

Mylan Mylan N.V. was a global generic and specialty pharmaceuticals company. In November 2020, Mylan merged with Upjohn, Pfizer's off-patent medicine division, to form Viatris. Previously, the company was domiciled in the Netherlands, with princip ...

still sold it. It is not widely used in humans as it has a high rate (30-60%) rate of gastrointestinal side effects.

Adverse effects

In October 2020, the U.S.

Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a federal agency of the Department of Health and Human Services. The FDA is responsible for protecting and promoting public health through the control and supervision of food ...

(FDA) required the drug label to be updated for all nonsteroidal anti-inflammatory medications to describe the risk of kidney problems in unborn babies that result in low

amniotic fluid The amniotic fluid is the protective liquid contained by the amniotic sac of a gravid amniote. This fluid serves as a cushion for the growing fetus, but also serves to facilitate the exchange of nutrients, water, and biochemical products betwe ...

. They recommend avoiding NSAIDs in pregnant women at 20 weeks or later in pregnancy.

Use in horses

Meclofenamic acid is sold under the trade name "Arquel" for use in horses, and is administered as an oral granule form at a dose of 2.2 mg/kg/day. It has a relatively slow onset of action, taking 36–48 hours for full effect, and is most useful for treatment of chronic musculoskeletal disease. It has been found to be beneficial for the treatment of navicular syndrome,

laminitis Laminitis is a disease that affects the feet of ungulates and is found mostly in horses and cattle. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperature in the hooves. Seve ...

, and

osteoarthritis Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone which affects 1 in 7 adults in the United States. It is believed to be the fourth leading cause of disability in the ...

, in some cases having a more profound effect than the commonly used NSAID phenylbutazone. However, due to cost, it is not routinely used in practice. Toxicity due to excessive dosage is similar to that of phenylbutazone, including depression,

anorexia Anorexia nervosa, often referred to simply as anorexia, is an eating disorder characterized by low weight, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. ''Anorexia'' is a term of Gre ...

, weight loss,

edema Edema, also spelled oedema, and also known as fluid retention, dropsy, hydropsy and swelling, is the build-up of fluid in the body's tissue. Most commonly, the legs or arms are affected. Symptoms may include skin which feels tight, the area ma ...

diarrhea Diarrhea, also spelled diarrhoea, is the condition of having at least three loose, liquid, or watery bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin ...

, oral ulceration, and decreased

hematocrit The hematocrit () (Ht or HCT), also known by several other names, is the volume percentage (vol%) of red blood cells (RBCs) in blood, measured as part of a blood test. The measurement depends on the number and size of red blood cells. It is nor ...

References

{{Ion channel modulators Anthranilic acids Chlorobenzenes Equine medications GABAA receptor positive allosteric modulators