Diclofenac

Diclofenac is prescribed to treat:

• Arthritis pain, inflammation, and acute pain • Various related conditions in the pain management category • Associated symptoms and complications

It is an important medication that helps manage these conditions effectively.

Diclofenac (Voltaren, Cataflam) is a non-steroidal anti-inflammatory drug used for osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, and acute pain. Its topical gel formulation is available over the counter and deserves separate consideration from the oral form, because the two carry substantially different risk profiles for the same active drug.

Mechanism of Action

Diclofenac inhibits cyclooxygenase, reducing prostaglandin synthesis and therefore inflammation, pain sensitisation, and fever. It has relatively greater COX-2 than COX-1 activity among the traditional NSAIDs — more selective than ibuprofen or naproxen, though less so than celecoxib.

That partial selectivity is a mixed inheritance. It contributes to good anti-inflammatory potency and somewhat less gastrointestinal injury than fully non-selective agents at equivalent effect. But because the cardiovascular risk of NSAIDs arises from COX-2 inhibition — removing endothelial prostacyclin while leaving platelet thromboxane intact — greater COX-2 selectivity means greater cardiovascular risk. Diclofenac consistently appears at the least favourable end of NSAID cardiovascular comparisons, with risk resembling that of the withdrawn COX-2 inhibitors more than that of naproxen.

This matters for prescribing. In a patient with cardiovascular disease requiring an NSAID, diclofenac is among the poorer oral choices, and naproxen is generally preferred.

Topical Versus Oral

The topical gel is where diclofenac is genuinely distinctive, and the difference is not marginal. Applied to a superficial joint, it achieves therapeutic concentrations in local tissue while producing systemic levels a small fraction of those from oral dosing. The consequence is meaningful analgesia in knee and hand osteoarthritis with substantially reduced gastrointestinal, renal, and cardiovascular exposure.

Guidelines now recommend topical NSAIDs ahead of oral ones for knee and hand osteoarthritis, particularly in patients over 75 — and this is one of the more under-implemented recommendations in outpatient practice. A patient taking oral diclofenac daily for knee arthritis, with hypertension and reduced kidney function, is frequently a patient who would do as well on the gel with a fraction of the risk.

Topical use suits joints close to the skin surface. It is less effective for deep joints such as the hip, where the drug cannot reach in useful concentration. Local skin reactions are the main adverse effect, and systemic effects, while much reduced, are not zero with extensive long-term application. The knee osteoarthritis article covers where it fits among non-surgical options.

Clinical Use

Oral diclofenac is effective for inflammatory arthritis and acute pain, but given its cardiovascular profile it is rarely the first oral NSAID to reach for. Where an oral NSAID is needed, the choice should follow the patient's dominant risk: naproxen where cardiovascular risk leads, celecoxib with gastroprotection where gastrointestinal risk leads.

For localised joint pain, the topical form should generally be tried before any oral NSAID. For pain without an inflammatory component, acetaminophen is safer. Our musculoskeletal team manages long-term arthritis care and can advise on which route fits.

Monitoring and Follow-Up

Oral use warrants periodic kidney function checks, blood pressure monitoring, and hemoglobin, since occult gastrointestinal blood loss can produce iron deficiency anemia before visible bleeding. Diclofenac is associated with hepatotoxicity more than other NSAIDs, so liver enzymes should be checked at baseline and periodically — elevations are usually mild and transient, but significant injury occurs and warrants stopping.

Gastroprotection with a proton pump inhibitor such as pantoprazole is appropriate in higher-risk patients. NSAIDs blunt most antihypertensives and, combined with an ACE inhibitor or ARB and a diuretic, produce acute kidney injury.

Topical use requires far less monitoring, though patients using large amounts over large areas for prolonged periods are not entirely free of systemic effects. The MedlinePlus diclofenac entry covers prescribing detail, and the FDA NSAID safety communication sets out the class warning.

Application technique determines whether the topical form works. The gel needs to be applied to clean, dry, intact skin over the affected joint, rubbed in, and the hands washed afterwards unless the hands are the treated site. Dosing cards are supplied precisely because patients otherwise apply a token amount and conclude it is ineffective. It should not be used with occlusive dressings or heat, both of which increase systemic absorption, and it should be kept away from the eyes and mucous membranes. Onset is gradual over days rather than immediate, which is worth saying in advance.

Special Populations

In older adults, the topical form is often the better choice for accessible joints, precisely because oral NSAID risks are amplified in this group. In chronic kidney disease and heart failure, oral NSAIDs are generally avoided.

In pregnancy, diclofenac is avoided from 20 weeks because of fetal renal effects and contraindicated in the third trimester. It is contraindicated after coronary bypass surgery, in active gastrointestinal bleeding, and in aspirin-exacerbated respiratory disease. Existing liver disease warrants particular caution given the hepatotoxicity signal.

Formulations differ more than the shared name suggests. Oral diclofenac exists as immediate-release, delayed-release, and extended-release tablets with different onset profiles, and as diclofenac potassium, which is absorbed faster than the sodium salt and is used where speed matters. The topical range includes a gel, a solution, and a patch. Substituting one for another because the active ingredient matches can change both onset and total exposure, so the specific product is worth confirming rather than assuming.

When to Contact Your Doctor

Seek urgent care for chest pain, sudden weakness, difficulty speaking, or vision change. Report black or tarry stools, vomiting blood or coffee-ground material, or severe abdominal pain. Yellowing of the skin or eyes, dark urine, persistent nausea with right upper abdominal pain, or unusual fatigue may indicate liver injury and warrant prompt testing.

Reduced urine output, new swelling, or rapid weight gain suggest fluid retention or kidney injury. With the topical gel, report significant skin irritation, rash, or blistering at the application site.

To review which NSAID and which route best fit your risk profile, or to discuss alternatives, contact us or schedule a visit.