Diclofenac
An acetic acid NSAID used for arthritis, ankylosing spondylitis, sprains, back pain and migraine, by mouth or as a gel on the skin.
Drug card
- Class
- NSAID
- How it works
- Blocking COX-1 and COX-2, so less prostaglandin is made
- Used for
- Osteoarthritis
- Rheumatoid arthritis
- Ankylosing spondylitis
- Sprains, back pain and pain after dental surgery
- Known for
- Stomach and duodenal ulcers
- Liver injury, with raised liver enzymes
- Heart attack and stroke
- Its name
- -ac means an acetic acid NSAID (diclofenac type)
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does diclofenac work?
Diclofenac, a benzeneacetic acid derivative, blocks COX-1 and COX-2 and strongly inhibits prostaglandin synthesis; it may act more on COX-2 than several other NSAIDs. As a gel or patch it works mainly where it is applied, and less of the drug reaches the blood.
Like other non-steroidal anti-inflammatory drugs: NSAIDs block the cyclooxygenase enzymes COX-1 and COX-2, which turn arachidonic acid into prostaglandins and thromboxane. With less prostaglandin, nerve endings are less sensitized, inflammation settles and fever falls. Losing COX-1 products in the stomach and platelets, and the prostaglandins that keep blood flowing through the kidney, explains their ulcers, bleeding and kidney harm.
Uses
What is diclofenac used for?
- Osteoarthritis
- Rheumatoid arthritis
- Ankylosing spondylitis
- Sprains, back pain and pain after dental surgery
- Migraine attacks
Side effects
Side effects of diclofenac
- Stomach and duodenal ulcersKnown forSerious
- Liver injury, with raised liver enzymesKnown forSerious
- Heart attack and strokeKnown forSerious
- Nausea and vomiting
- Indigestion and stomach pain
- Diarrhea
- Dizziness and vertigo
- Rash
- Bleeding from the stomach or gutSerious
- Worsening heart failureSerious
- Acute kidney injurySerious
- Allergic reactions, including anaphylaxisSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Avoid after a heart attack or stroke and in heart failure or arterial disease: its cardiovascular risk matches the coxibs'.
- Liver enzymes rise more often than with other NSAIDs; check liver tests at the start and during long-term use.
- Avoid with a past ulcer or GI bleeding, and limit or avoid in pregnancy from about 20 weeks.
Good to know: EMA judged its risk of heart attack and stroke to exceed that of other non-selective NSAIDs and to match the selective COX-2 inhibitors', so the same precautions apply.
Remember it
A way to remember it
NSAID
- N
- Nephrotoxicity: acute kidney injury
- S
- Stomach ulcers and bleeding
- A
- Asthma attacks in aspirin-sensitive people
- I
- Increased risk of heart attack and stroke
- D
- Ductus arteriosus closing early in late pregnancy
Written for biofideX
Its name
-ac means acetic acid NSAID (diclofenac type)
Diclofenac and aceclofenac (-clofenac), bromfenac (-fenac), etodolac (-dolac), ketorolac and sulindac all end in -ac. Tolmetin, from the same group, lacks it.
- Every drug name stem
Its class
Non-steroidal anti-inflammatory drugs
Easily mixed up with selective COX-2 inhibitors, paracetamol and glucocorticoids.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Diclofenac sodium delayed-release tablets: label (DailyMed)
- Diclofenac (NCI Thesaurus)
- Diclofenac (NHS)
- Diclofenac-containing medicines: referral (EMA)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Pain, fever and inflammation
Diclofenac is one of 15 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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