Diclofenac: tablets, gel and plasters explained

Diclofenac is an NSAID that reduces pain and swelling. The NHS lists ankylosing spondylitis, gout, migraine, osteoarthritis and rheumatoid arthritis as conditions it treats, and says it is also used for sprains, back pain and after dental surgery. It works by reducing hormones that cause inflammation and pain.

There is also a stronger gel used for sun-damaged skin patches, started after dermatology assessment; that use is outside this guide.

Because gel, plasters and patches act mainly where they are applied, they are generally less likely to cause side effects than tablets. Tablets give whole-body exposure, which is why the long-term warnings concentrate on them.

• Tablets and capsules: prescription-only. Swallow with milk, or with water after a meal or snack. Slow-release versions are sometimes used for constant pain, with 10 to 12 hours between doses if taken twice daily. Swallow whole.

• Suppositories: prescription-only, inserted gently into the back passage, usually 1 to 3 times a day depending on strength.

• Gel: a cherry- or walnut-sized amount (2 to 4 grams) rubbed into the sore area 2 to 4 times a day depending on strength, never more than 4 times in 24 hours. For arthritis it can take up to 7 days on the joint to feel the full effect.

• Plasters and patches: one painful area at a time, up to 2 in 24 hours, usually morning and evening.

More than 1 in 100 people on tablets, capsules or suppositories get nausea or vomiting, diarrhoea, dizziness or vertigo, headaches, stomach ache, wind, loss of appetite or a mild rash. The NHS gives practical tips for each, such as taking diclofenac after eating and drinking fluids if you have diarrhoea. Gel and plaster users may notice sun sensitivity, itching or dry irritated skin.

Rare serious effects happen in fewer than 1 in 1,000 people. Call a doctor or 111 for black stools, severe indigestion or stomach pain, yellowing of the skin or whites of the eyes, a raised itchy rash or swelling, or breathlessness with swollen legs. Call 999 for vomiting blood, signs of a heart attack or stroke, or anaphylaxis.

Tell a doctor or pharmacist if you have had an allergic reaction to diclofenac or other medicines, are allergic to aspirin or other NSAIDs, have asthma, have had stomach ulcers or bleeding, have high blood pressure, heart failure, severe liver disease or kidney disease, Crohn disease or ulcerative colitis, lupus or a clotting disorder, or are pregnant, planning pregnancy or breastfeeding.

Long courses of tablets can cause stomach ulcers, and the NHS notes a small risk of heart or kidney failure at the maximum dose over a long time. For people who need an NSAID long term, ibuprofen or naproxen may be recommended instead because they are less likely to cause heart problems. A doctor may add a stomach-protecting medicine.

Diclofenac is not usually recommended in pregnancy because it can affect blood flow in the baby and reduce amniotic fluid. A doctor will only advise it if the benefit outweighs the risk, and then only for a few days. Paracetamol is generally the first choice.

It can be used while breastfeeding, as only tiny amounts reach the milk. Large doses or long courses of anti-inflammatories can affect ovulation, so you may wish to avoid it if you are trying to conceive. It does not affect contraceptives, although severe sickness or diarrhoea can.

Speak to a pharmacist before starting if you take quinolone antibiotics such as ciprofloxacin, anticoagulants such as warfarin, digoxin, blood pressure medicines, colestipol or cholestyramine, phenytoin, ciclosporin or tacrolimus, SSRIs such as citalopram or sertraline, steroids, diuretics such as furosemide, lithium, methotrexate, mifepristone or zidovudine. It is safe with paracetamol or codeine but not with aspirin, ibuprofen or naproxen without medical advice.

You can drink alcohol, staying within 14 units a week, though heavy drinking can irritate the stomach. If diclofenac makes you tired, dizzy or sleepy, or affects your eyesight, do not drive or cycle until it passes.