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 th ...

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

nonsteroidal anti-inflammatory drugs A nonsteroidal compound is a drug that is not a steroid nor a steroid derivative. Nonsteroidal anti-inflammatory drugs (NSAIDs) are distinguished from corticosteroids as a class of anti-inflammatory agents. List of nonsteroidal steroid receptor mod ...

(NSAIDs) and was approved by the US

FDA 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 ...

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 biosynthesis of prostanoids, including thromboxane and prostaglandins such a ...

(COX) inhibitor, preventing the formation of

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

. Scientists led by Claude Winder from

Parke-Davis Parke-Davis is a subsidiary of the pharmaceutical company Pfizer. Although Parke, Davis & Co. is no longer an independent corporation, it was once America's oldest and largest drug maker, and played an important role in medical history. In 1970 ...

invented meclofenamate sodium in 1964, along with fellow members of the class,

mefenamic acid Mefenamic acid is a member of the Nonsteroidal anti-inflammatory drug#Anthranilic acid derivatives .28fenamates.29, anthranilic acid derivatives (or fenamate) class of nonsteroidal anti-inflammatory drugs (NSAIDs), and is used to treat mild to m ...

in 1961 and flufenamic acid 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 principa ...

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 List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...

(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 betwee ...

. 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 Navicular syndrome, often called navicular disease, is a syndrome of lameness problems in horses. It most commonly describes an inflammation or degeneration of the navicular bone and its surrounding tissues, usually on the front feet. It can lead ...

laminitis Laminitis is a disease of the feet of ungulates, found mostly in horses and cattle involving inflammation of the laminae. Clinical signs include foot tenderness progressing to inability to walk, increased digital pulses, and increased temperatur ...

, and

osteoarthritis Osteoarthritis is a type of degenerative joint disease that results from breakdown of articular cartilage, joint cartilage and underlying bone. A form of arthritis, it is believed to be the fourth leading cause of disability in the world, affect ...

, in some cases having a more profound effect than the commonly used NSAID

phenylbutazone Phenylbutazone, often referred to as "bute", is a nonsteroidal anti-inflammatory drug (NSAID) for the short-term treatment of pain and fever in animals. In the United States and United Kingdom, it is no longer approved for human use (except in t ...

. 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 (AN), often referred to simply as anorexia, is an eating disorder characterized by Calorie restriction, food restriction, body image disturbance, fear of gaining weight, and an overpowering desire to be thin. Individuals wit ...

, weight loss,

edema Edema (American English), also spelled oedema (British English), and also known as fluid retention, swelling, dropsy and hydropsy, is the build-up of fluid in the body's tissue (biology), tissue. Most commonly, the legs or arms are affected. S ...

diarrhea Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day. It often lasts for a few days and can result in dehydration d ...

, 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 Chlorobenzene derivatives Equine medications GABAA receptor positive allosteric modulators