Diclofenac

Diclofenac is a commonly used drug from the group of non-steroidal anti-inflammatory drugs (NSAIDs). It is used to treat mild to moderate pain and inflammation, mainly after injuries such as bruises or strains. Diclofenac is most commonly administered in the sodium salt form. Common dosage forms include gels and ointments for external use, as well as tablets. Diclofenac is available by prescription in certain dosage forms.

Pharmacodynamics

Diclofenac works by inhibiting a specific enzyme in the body. This enzyme, cyclooxygenase, is instrumental in the development of pain. Diclofenac binds to the enzyme and inhibits its function, thereby preventing the synthesis of prostaglandins. Prostaglandins mediate inflammatory processes, which subsequently lead to the development of pain. This results in the analgesic, anti-inflammatory and also antipyretic effect of diclofenac.

Pharmacokinetics

Diclofenac is absorbed in the GI tract, but experiences a strong "first-pass effect", which is why only about 60% reaches the bloodstream. For this reason, diclofenac is most commonly applied to the skin, as this circumvents the "first-pass effect". The maximum plasma concentration is reached after 1-2 hours on average. Diclofenac is 99% bound to plasma proteins and is mainly metabolized by the liver. Excretion is 70% by the kidneys and 30% by the stool.

Drug Interactions

Concomitant administration of other NSAIDs or glucocorticoids may increase the risk of gastrointestinal bleeding. Diclofenac may inhibit the action of diuretics and angiotensin II antagonists. Diclofenac may increase serum levels of lithium, phenytoin and cardiac glycosides.

Side effects

The typical side effects involve the gastrointestinal tract and include, for example, abdominal pain and nausea, as well as bleeding.

Other side effects are:

• Vomiting
• Diarrhoea
• Flatulence
• constipation
• indigestion
• abdominal pain
• tarry stools
• Hematemesis

Toxicological data

LD50 (rat, oral): 62.5 mg-kg-1