Diclofenac — NZ Medication Guide
📋 Reviewed by a Registered Pharmacist NZ — This information is for general educational purposes only and does not replace professional medical advice. Always consult your doctor or pharmacist before starting, stopping, or changing any medication.
What is Diclofenac?
Diclofenac is a non-steroidal anti-inflammatory drug (NSAID) used for pain relief and anti-inflammatory treatment. This medication is oral diclofenac funded by Pharmac; topical diclofenac available over-the-counter.
What is Diclofenac Used For?
Diclofenac is used for musculoskeletal pain (arthritis, back pain, sprains, strains), dysmenorrhoea (painful periods), dental pain, post-operative pain, and inflammatory conditions. Topical diclofenac gel is used for localised musculoskeletal pain with fewer systemic side effects.
How Does Diclofenac Work?
Diclofenac inhibits both cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) enzymes, reducing the synthesis of prostaglandins — the mediators responsible for pain, inflammation, and fever. Diclofenac has slightly greater COX-2 selectivity than ibuprofen, which may explain a marginally lower GI side effect profile at equipotent doses.
How to Take Diclofenac
Oral: 25–50 mg two to three times daily or 75 mg modified-release once or twice daily. Take with food to reduce gastric upset. Topical gel (Voltaren® 1% or 2%): apply 2–4 g to the affected area 3–4 times daily. Do not use topical gel on broken skin. Suppository formulation also available.
Common Side Effects of Diclofenac
- Gastric upset, nausea, dyspepsia
- Headache
- Dizziness
- Elevated liver enzymes (more common with diclofenac than other NSAIDs)
- Fluid retention
- Rash
Serious Side Effects — Seek Medical Attention
Contact your doctor or call 111 immediately if you experience any of the following:
- Gastrointestinal ulceration and bleeding (significant — use PPI prophylaxis if GI risk factors present)
- Cardiovascular events — MI and stroke (modest increased risk with long-term use — particularly relevant in patients with CVD)
- Renal impairment (particularly in volume-depleted or renal-impaired patients)
- Serious liver toxicity (diclofenac has higher hepatotoxicity risk than most NSAIDs)
- Severe skin reactions
Drug Interactions
Diclofenac may interact with other medicines. Always inform your doctor and pharmacist of all medications you are taking. Key interactions include:
- Anticoagulants (warfarin, DOACs — increased bleeding risk)
- ACE inhibitors/ARBs (reduce antihypertensive effect and increase renal risk)
- Methotrexate (reduced excretion — toxicity risk)
- Lithium (increased levels)
- Diuretics (reduced efficacy and renal risk)
New Zealand Prescribing Information
Diclofenac (25 mg, 50 mg tablets; 75 mg modified-release tablets; 100 mg suppositories — Voltaren® and generics) is funded by Pharmac for oral use. Topical Voltaren® Emulgel® and Voltaren® Osteo Gel® are available over-the-counter. Diclofenac carries a higher hepatotoxicity risk than most other NSAIDs — LFT monitoring is recommended with prolonged use. In NZ, ibuprofen or naproxen are generally preferred for mild-to-moderate pain due to better GI and hepatic safety profiles.
Frequently Asked Questions
Is diclofenac gel as effective as the tablets?
Topical diclofenac gel (Voltaren® Emulgel®) achieves local tissue concentrations sufficient for pain relief in superficial musculoskeletal conditions (knee and hand osteoarthritis, soft tissue sprains) with significantly lower systemic absorption and fewer GI and cardiovascular side effects. It is a good option for localised pain in older adults.
Does diclofenac affect the liver?
Diclofenac has a slightly higher risk of liver enzyme elevation and hepatotoxicity compared to other commonly used NSAIDs. Liver function should be monitored with prolonged use. Diclofenac should be used with caution in patients with liver disease.
⚠️ Disclaimer: This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your doctor or a qualified health provider. In New Zealand, medication availability and funding may vary — check with Pharmac or your pharmacist for current information.
Reviewed by a Registered Pharmacist NZ
References & Further Information
The following New Zealand and international resources were used to inform this page: