Fenactol (Diclofenac)

How does it work?

Fenactol e/c tablets, Fenactol SR tablets and Fenactol retard tablets all contain the active ingredient diclofenac sodium, which is a type of medicine called a non-steroidal anti-inflammatory drug (NSAID). NSAIDs are used to relieve pain and inflammation. (NB. Diclofenac is also available without a brand name, ie as the generic medicine.)

Diclofenac works by blocking the action of a substance in the body called cyclo-oxygenase (COX). Cyclo-oxygenase is involved in the production of various chemicals in the body, some of which are known as prostaglandins. Prostaglandins are produced by the body in response to injury and certain diseases and conditions, and cause pain, swelling and inflammation. Diclofenac blocks the production of these prostaglandins and is therefore effective at reducing inflammation and pain.

Diclofenac is used to relieve pain and inflammation in a wide range of musculoskeletal conditions, including various forms of arthritis, gout, sprains, fractures, dislocations, back pain, tendinitis and frozen shoulder. It is also used to relieve pain and inflammation following dental, orthopaedic (bone) and other minor surgery.

Fenactol e/c tablets have a special 'enteric coating' that is designed to prevent the absorption of the diclofenac in the stomach, and thus reduce the risk of stomach irritation. The diclofenac is absorbed when the tablet reaches the intestine. The tablets should be swallowed whole to avoid damaging this coating.

Fenactol SR and Fenactol retard tablets are modified-release tablets. They contain higher doses of diclofenac and are designed to release this slowly and continuously over a few hours. This provides more prolonged pain relief, so these tablets are usually taken once or twice a day. These tablets must also be swallowed whole to avoid damaging the modified-release action.

All types of Fenactol tablet should preferably be taken with food to help avoid irritating the stomach.

What is it used for?

Fenactol tablets are used to relieve pain and inflammation in a wide range of conditions in adults, including those listed below.

  • Rheumatoid arthritis.
  • Osteoarthritis.
  • A form of arthritis affecting the joints of the spine (ankylosing spondylitis).
  • Acute gout.
  • Acute disorders of the muscles and skeleton, such as frozen shoulder (periarthritis), tendon inflammation (tendinitis), tenosynovitis, bursitis.
  • Painful conditions due to accidents, such as sprains, strains, dislocations, fractures.
  • Lower back pain.
  • Pain and inflammation following dental, orthopaedic (bone) and other minor surgery.

How do I take it?

  • The dose prescribed and how often to take the medicine depends on your level of pain and inflammation and the type of tablet you have been prescribed. It is important to follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the packet of medicine. If you are unsure about anything, talk to your pharmacist.
  • Fenactol e/c tablets, Fenactol SR tablets and Fenactol Retard tablets should be swallowed whole with a drink and not broken, crushed or chewed. They should preferably be taken with or after food.
  • Don't take indigestion remedies (antacids) at the same time of day as the e/c tablets. This is because antacids stop the special enteric coat from working.
  • Try to space your doses evenly. If you forget to take a dose at your usual time take it as soon as you remember, unless it is nearly time for your next dose. In this case just leave out the forgotten dose and take the next dose as usual. Do not take a double dose to make up for a missed dose.


  • This medicine may cause dizziness, drowsiness or visual disturbances and so may affect your ability to drive or operate machinery safely. Do not drive or operate machinery until you know how this medicine affects you and you are sure it won't affect your performance.
  • This medicine may mask the signs and symptoms of infection, such as fever and inflammation. This may make you think mistakenly that an infection is getting better when it isn't, or that an infection is less serious than it is. For this reason you should tell your doctor if you get an infection while you are taking this medicine.
  • Your doctor will prescribe you the lowest effective dose of this medicine for the shortest possible time necessary to relieve your symptoms. This is to minimise the chances of any side effects, particularly those mentioned below. It is important not to exceed the prescribed dose.
  • NSAIDs can occasionally cause serious side effects on the gut, such as ulceration, bleeding or perforation of the stomach or intestinal lining. This type of side effect is more likely to occur in elderly people and in people taking high doses of the medicine. The risk can also be increased by taking certain other medicines (see end of factsheet). It is important that these people, as well as people with a history of disorders affecting the stomach or intestines, are closely monitored by a doctor while taking this medicine. If your doctor thinks you are at high risk of side effects on the gut you may be prescribed an additional medicine to help protect your gut. All people having treatment with this medicine should stop taking it and consult their doctor immediately if they experience any sign of bleeding from the stomach or intestine, for example vomiting blood and/or passing black/tarry/bloodstained stools.
  • In recent years research has shown that use of diclofenac is associated with a small increase in the risk of having a heart attack or stroke. The risks increase with higher doses and the longer the medicine is taken. These risks are very rare and the benefits of the medicine for pain relief still outweigh these risks for most people. However, if you have existing heart or blood vessel disease (see below) the latest advice is that diclofenac is not suitable for you. Your doctor can prescribe you a different painkiller that has lower risks for you. If you have risk factors for heart disease or stroke, such as diabetes, high blood pressure, high cholesterol or smoking, your doctor will need to assess the overall benefits and risks before deciding if this medicine is suitable for you. Ask your doctor or pharmacist for further information.
  • Very rarely, NSAIDS may cause serious blistering or peeling skin reactions (eg Stevens-Johnson syndrome, toxic epidermal necrolysis, exfoliative dermatitis). For this reason, you should stop taking this medicine and consult your doctor if you get a skin rash, skin peeling or sores inside your mouth while taking this medicine. This side effect is very rare, but if it occurs, is most likely to happen in the first month of treatment.
  • If you have cirrhosis of the liver, heart failure or kidney disease, you are taking diuretic medicines, or you are recovering from major surgery, your kidney function should be assessed before starting and regularly throughout treatment with this medicine.
  • During long-term treatment with this medicine you should have regular check-ups with your doctor so that you can be monitored for possible side effects of the medicine. This might include routine blood tests to monitor your kidney function, liver function and levels of blood components, particularly if you are elderly.

Use with caution in

  • Elderly people.
  • People with a history of disorders affecting the stomach or intestines, such as ulceration or bleeding.
  • Inflammatory bowel disease such as Crohn's disease or ulcerative colitis.
  • Decreased kidney function.
  • Decreased liver function.
  • A type of life long inherited blood disease caused by a defect in the liver (hepatic porphyria).
  • People with a history of high blood pressure (hypertension).
  • People with raised levels of fats such as cholesterol in their blood (hyperlipidaemia).
  • Diabetes.
  • Smokers.
  • History of asthma.
  • History of allergies.
  • People with blood clotting disorders or taking anticoagulant medicines.
  • Diseases affecting connective tissue, eg systemic lupus erythematosus.

Not to be used in

  • People in whom aspirin or other NSAIDs, eg ibuprofen, cause allergic reactions such as asthma attacks, itchy rash (urticaria), nasal inflammation (rhinitis) or swelling of the lips, tongue and throat (angioedema).
  • People with an active peptic ulcer, perforation (hole) or bleeding in the gut.
  • People who have had recurrent peptic ulcers or bleeding from the gut (two or more episodes).
  • People who have previously experienced bleeding or perforation of the gut as a result of taking an NSAID.
  • Heart failure.
  • Heart disease caused by inadequate blood flow to the heart (ischaemic heart disease), eg angina or history of heart attack.
  • People with disease of the blood vessels in and around the brain (cerebrovascular disease), eg history of stroke or mini-stroke (TIA).
  • People with poor circulation in the arteries of the legs or feet (peripheral arterial disease).
  • Severe liver failure.
  • Severe kidney failure.
  • Third trimester of pregnancy.
  • Fenactol e/c tablets, Fenactol SR tablets and Fenactol retard tablets are not licensed for children.
  • Fenactol e/c and Fenactol SR tablets contain lactose and are not suitable for people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption.
  • Fenactol retard tablets contain sucrose and are not suitable for people with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine should not be taken in the third trimester of pregnancy because it may delay labour, increase the length of labour and cause complications in the newborn baby. It is not recommended for use in the first and second trimesters of pregnancy unless considered essential by your doctor. Some evidence suggests that NSAIDs such as this one should also be avoided by women attempting to conceive, as they may temporarily reduce female fertility during treatment and may also increase the risk of miscarriage or malformations. Ask your doctor for further advice.
  • The medicine passes into breast milk in small amounts. At normal doses it is unlikely to harm the baby, however it is important to discuss this with your doctor before taking this medicine if you are breastfeeding.

Label warnings

  • Take this medication with or after food.
  • This medication is to be swallowed whole, not chewed.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Common (affect between 1 in 10 and 1 in 100 people)

  • Disturbances of the gut such as diarrhoea, nausea, vomiting, indigestion, abdominal pain or wind (flatulence).
  • Loss of appetite.
  • Headache.
  • Dizziness.
  • Spinning sensation.
  • Skin rashes.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Ulceration or bleeding in the stomach or intestine - see warning section above.
  • Inflammation of the stomach (gastritis).
  • Sleepiness or tiredness.
  • Shortness of breath or asthma attack.
  • Fluid retention (oedema).
  • Hives (urticaria or nettle rash).
  • Inflammation of the liver (hepatitis).
  • Yellowing of the skin and whites of the eyes (jaundice).

Very rare (affect fewer than 1 in 10,000 people)

  • Visual disturbances such as blurred or double vision.
  • Sensation of ringing or other noise in the ears (tinnitus).
  • Hearing impairment.
  • Severe swelling of the face, throat, lips and tongue (angioedema).
  • Difficulty sleeping (insomnia) or nightmares.
  • Irritability, depression or anxiety.
  • Feeling confused or disorientated.
  • Tremor.
  • Taste disturbances.
  • Pins and needles sensations.
  • Changes in blood pressure.
  • Stroke (cerebrovascular accident).
  • Chest pain or palpitations.
  • Heart attack (myocardial infarction) or heart failure - see warning section above.
  • Severe allergic skin reactions - see warning section above.
  • Kidney problems, including acute kidney failure.
  • Liver problems, including liver failure.
  • Inflammation of the bowel (colitis) or pancreas (pancreatitis).
  • Decreased numbers of white blood cells, red blood cells or platelets in the blood.
  • Erectile dysfunction (impotence).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before taking this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

Indigestion remedies such as antacids should not be taken at the same time as enteric-coated diclofenac tablets. This is because they reduce the acidity in the stomach and allow the enteric coat to dissolve there instead of in the intestine.

Diclofenac should not be taken in combination with painkilling doses of aspirin or any other oral NSAID, eg ibuprofen, naproxen, as this increases the risk of side effects on the stomach and intestines. Selective inhibitors of COX-2 such as celecoxib or etoricoxib should also be avoided for the same reason.

There may be an increased risk of ulceration or bleeding from the gut if diclofenac is taken with oral corticosteroids such as prednisolone.

There may be an increased risk of bleeding, particularly from the gut, if diclofenac is taken with any of the following medicines:

  • anti-blood-clotting (anticoagulant) medicines such as warfarin, dabigatran, heparin
  • anti-platelet medicines to reduce the risk of blood clots or 'thin the blood', eg low-dose aspirin, clopidogrel, dipyridamole
  • erlotinib
  • iloprost
  • prasugrel
  • SSRI antidepressants, eg fluoxetine, paroxetine, citalopram
  • venlafaxine.

Diclofenac may reduce the removal of the following medicines from the body and so may increase the blood levels and risk of side effects of these medicines. People taking diclofenac with any of these should be closely monitored by their doctor:

  • digoxin
  • lithium
  • methotrexate.

There may be an increased risk of side effects on the kidneys if diclofenac is taken with any of the following medicines:

  • ACE inhibitors, eg enalapril
  • aliskiren
  • angiotensin II receptor antagonists, eg losartan
  • ciclosporin
  • diuretics, eg furosemide
  • tacrolimus.

Diclofenac may oppose the blood pressure lowering effects of certain medicines to treat high blood pressure, such as the following:

  • ACE inhibitors such as captopril
  • aliskiren
  • angiotensin II receptor antagonists, eg losartan
  • beta-blockers such as propranolol
  • diuretics such as furosemide.

There may be an increased risk of seizures (fits) if diclofenac is used in combination with quinolone antibiotics, such as ciprofloxacin or ofloxacin.

Ciclosporin and the antifungal voriconazole may both increase the blood level of diclofenac, and your doctor may prescribe a lower than normal dose of diclofenac if you are taking one of these.

Rifampicin may increase the breakdown of diclofenac and it may be less effective in people taking this medicine for tuberculosis.

Other medicines containing the same active ingredient

Prescription only products:

  • Dicloflex, Dicloflex SR and Dicloflex retard.
  • Diclomax SR and Diclomax retard.
  • Dyloject.
  • Econac injection.
  • Econac suppositories.
  • Econac SR and Econac XL.
  • Flamatak MR.
  • Flamrase SR.
  • Motifene.
  • Pennsaid cutaneous solution.
  • Rheumatac retard.
  • Rhumalgan CR, Rhumalgan SR and Rhumalgan XL.
  • Volsaid retard.
  • Voltarol e/c, dispersible, SR and retard tablets.
  • Voltarol emulgel.
  • Voltarol gel patch.
  • Voltarol injection.
  • Voltarol ophtha.
  • Voltarol rapid tablets.
  • Voltarol suppositories.

Diclofenac enteric-coated tablets, sustained-release tablets, suppositories and injection are also available without brand names, ie as the generic medicine.

Arthrotec contains diclofenac in combination with a stomach-protecting medicine called misoprostol.

Non-prescription products:

    Taken by mouth
  • Boots joint pain relief 12.5mg tablets.
  • Voltarol joint pain 12.5mg tablets.
  • Voltarol pain-eze 12.5mg tablets.
  • Voltarol pain-eze extra strength 25mg tablets.
    Applied to skin
  • Voltarol active 4% cutaneous spray.
  • Voltarol emulgel P.
  • Voltarol pain-eze emulgel.