Diclofenac SR

Diclofenac (Voltarol) is a non-steroidal anti-inflammatory drug (NSAID) widely used for the relief of pain, inflammation, and swelling associated with a variety of musculoskeletal and other conditions. It is available in multiple formulations including oral tablets (standard and modified-release), suppositories, and topical gel preparations, providing flexibility to tailor treatment to the nature and site of pain. Diclofenac is one of the most commonly prescribed analgesics in the UK and is used across a broad range of clinical settings.

Conditions Treated

Diclofenac is indicated for the treatment of pain and inflammation in conditions including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, acute gout, soft tissue injuries such as sprains and strains, post-operative or post-traumatic pain, dysmenorrhoea (painful periods), and renal colic. Topical diclofenac gel (Voltarol Emulgel) is available over the counter for the relief of localised musculoskeletal pain in adults, offering targeted anti-inflammatory action with a lower risk of systemic adverse effects compared with oral formulations.

Mechanism of Action

Diclofenac exerts its anti-inflammatory, analgesic, and antipyretic effects primarily by inhibiting the cyclooxygenase enzymes COX-1 and COX-2. These enzymes are responsible for converting arachidonic acid into prostaglandins, thromboxanes, and prostacyclin — mediators that sensitise pain receptors, promote inflammation, and regulate platelet function. By inhibiting both COX isoforms, diclofenac reduces prostaglandin synthesis at the site of injury, decreasing pain and inflammation. The relative COX-2 selectivity of diclofenac is higher than many other traditional NSAIDs, which is one reason it is associated with lower rates of GI mucosal injury at equivalent doses.

Diclofenac should always be used at the lowest effective dose for the shortest duration necessary. It should be taken with food or milk to minimise gastrointestinal irritation when used orally.

Oral Use

Oral diclofenac tablets are typically taken two to three times daily for standard-release formulations or once or twice daily for modified-release tablets. Tablets should be swallowed whole, not crushed or chewed, especially modified-release preparations. Diclofenac should be taken with or after food, and a large glass of water should be consumed with each dose to help prevent oesophageal irritation.

Topical Use

Voltarol Emulgel and similar topical diclofenac preparations should be applied to the affected area three to four times daily, rubbing gently into the skin until absorbed. Hands should be washed after each application unless the hands themselves are being treated. Topical diclofenac should not be applied to broken, infected, or damaged skin, or over extensive skin areas. Avoid contact with eyes and mucous membranes. The gel formulation provides effective local anti-inflammatory action with minimal systemic absorption, making it particularly suitable for patients in whom oral NSAIDs are contraindicated or who wish to minimise systemic side effects.

Patients with cardiovascular disease or risk factors should use the lowest effective dose of oral diclofenac for the shortest duration, and the benefit-risk balance should be reviewed regularly by the prescribing clinician.

For oral diclofenac, the usual adult dose is 75-150 mg per day in divided doses, depending on the condition being treated. For standard-release 25 mg and 50 mg tablets, dosing is typically two to three times daily. Modified-release formulations (75 mg or 100 mg) are taken once or twice daily. The maximum oral dose is generally 150 mg per day.

For topical Voltarol Emulgel, 2-4 g is applied to the affected area three to four times daily. The maximum total daily dose for topical preparations should follow product-specific guidance.

No dose adjustment is required based on age alone for mild to moderate conditions in elderly patients, but the lowest effective dose should be used given the increased cardiovascular, renal, and gastrointestinal risks in older adults. Diclofenac should be avoided in patients with significant renal or hepatic impairment. Prescription-strength oral diclofenac is not recommended in patients with established cardiovascular disease, and even over-the-counter topical preparations should be used cautiously in those at high cardiovascular risk.

Diclofenac is associated with a range of adverse effects, particularly with prolonged oral use. The risk of serious cardiovascular and gastrointestinal events increases with dose and duration of treatment.

Common Side Effects

• Nausea, dyspepsia, abdominal pain, diarrhoea, or constipation — particularly with oral formulations
• Headache and dizziness
• Elevated liver enzymes (usually transient and asymptomatic)
• Fluid retention and mild oedema
• Skin reactions: rash or itching
• With topical formulations: local skin reactions including pruritus, erythema, and occasional contact dermatitis

Serious Side Effects

Patients should seek urgent medical attention for:

• Gastrointestinal bleeding or perforation: black or tarry stools, vomiting blood, or severe abdominal pain may indicate a serious GI complication; these can occur without prior warning symptoms, particularly in elderly patients
• Cardiovascular events: diclofenac is associated with an increased risk of myocardial infarction and stroke, particularly at higher doses and with longer duration; this risk is present even in patients without prior cardiovascular disease
• Hepatotoxicity: rarely, severe liver reactions including jaundice and fulminant hepatitis can occur; unexplained fatigue, jaundice, or right upper quadrant pain should be investigated promptly
• Severe hypersensitivity: including anaphylaxis, Stevens-Johnson syndrome (a rare but serious skin reaction involving blistering and mucosal involvement)
• Renal impairment: NSAIDs can precipitate acute kidney injury, particularly in the elderly, dehydrated, or those with pre-existing renal disease

Diclofenac should be prescribed and used with care, particularly in patients with cardiovascular, gastrointestinal, or renal risk factors.

Cardiovascular Risk

Diclofenac carries a higher cardiovascular risk among traditional NSAIDs. Studies have shown that diclofenac at prescription doses (150 mg daily) is associated with a similar increase in the risk of major cardiovascular events (heart attack and stroke) as COX-2 selective inhibitors (coxibs). It must not be used in patients with established ischaemic heart disease, peripheral arterial disease, cerebrovascular disease, or congestive heart failure (NYHA II-IV). In patients with cardiovascular risk factors, the decision to prescribe oral diclofenac should be taken only after careful consideration.

Gastrointestinal Protection

Patients taking oral diclofenac who are at increased risk of GI complications — including the elderly, those with a prior history of peptic ulcer disease, those taking anticoagulants or low-dose aspirin, or those with other risk factors — should be co-prescribed a proton pump inhibitor (PPI) such as omeprazole or lansoprazole. NSAIDs should be taken with food and at the lowest effective dose for the shortest period.

Renal and Hepatic Monitoring

Renal function, hepatic enzymes, and blood pressure should be monitored during long-term oral diclofenac therapy. Volume depletion should be corrected before initiating treatment, particularly in elderly patients or those with cardiac failure.

Diclofenac must not be used in the following situations:

• Established ischaemic heart disease, peripheral arterial disease, or cerebrovascular disease (for oral formulations)
• Congestive heart failure (NYHA II-IV)
• Active or history of peptic ulcer or gastrointestinal bleeding
• Previous hypersensitivity (asthma, urticaria, angioedema) to diclofenac, aspirin, or any other NSAID
• Severe hepatic, renal, or cardiac impairment
• Third trimester of pregnancy (all NSAIDs)
• Inflammatory bowel disease (Crohn's disease, ulcerative colitis)
• Concurrent use of two or more NSAIDs (including aspirin at anti-inflammatory doses)
• Severe dehydration or hypovolaemia
• Children under 14 years (oral formulations)