Valproic acid (Convulex)

How does it work?

Convulex enteric-coated capsules contain the active ingredient valproic acid, which is a medicine that is used mainly to treat epilepsy. (NB. Valproic acid is another form of the antiepileptic medicine, sodium valproate. Both can be known simply as valproate.) Valproate works by stabilising electrical activity in the brain.

The brain and nerves are made up of many nerve cells that communicate with each other through electrical signals. These signals must be carefully regulated for the brain and nerves to function properly. When abnormally rapid and repetitive electrical signals are released in the brain, the brain becomes over-stimulated and normal function is disturbed. This results in fits or seizures.

Valproic acid works in the same way as sodium valproate; by preventing the excessive electrical activity in the brain. It is thought to achieve this by increasing the activity of a neurotransmitter called GABA in the brain.

Neurotransmitters are natural body chemicals that are stored in nerve cells and are involved in transmitting messages between the nerve cells. GABA is a neurotransmitter that acts as a natural 'nerve-calming' agent. It helps keep the nerve activity in the brain in balance.

Valproic acid is thought to increase the production and prevent the breakdown of GABA in the brain. This enhances the calming action of GABA in the brain, which stabilises the electrical nerve activity and helps prevent fits.

In addition to its licensed use for treating epilepsy, valproic acid is used off-licence by specialists as a mood stabiliser for treating people with the psychiatric illness, bipolar affective disorder. This use is not licensed, but valproate has been shown to be effective for controlling episodes of mania in this condition, and for helping prevent future episodes of ill health. It is not fully understood how valproic acid works as a mood stabiliser in bipolar disorder, but is thought to be to do with the increased activity of GABA in the brain.

What is it used for?

  • Epilepsy.
  • Treatment of acute manic episodes in bipolar affective disorder (unlicensed use).
  • As a mood stabiliser in bipolar affective disorder to help prevent episodes of mania or depression (unlicensed use).

Warning!

  • Convulex capsules should be swallowed whole and not broken, crushed or chewed.
  • This medicine may cause drowsiness, especially if it is taken with other antiepileptic medicines, or with benzodiazepines such as lorazepam. This may affect your ability to drive or operate machinary.
  • This medicine can cause some people to put on weight. Talk to your doctor about this before you start treatment so that you can discuss strategies, such as diet and exercise, for minimising any weight gain.
  • This medicine may on rare occasions affect your liver, pancreas or blood cells. You should have blood tests to monitor your liver function, blood cells and blood clotting time before you start treatment. Your liver function should be monitored for the first six months of treatment, and your blood cell count should be checked before any surgery. Tell your doctor immediately if you, or a child taking this medicine, experience any of the following symptoms during treatment, particularly if they come on suddenly or occur in the first six months of taking the medicine: lack of appetite and energy, weakness, feeling generally unwell, drowsiness, nausea, vomiting, severe abdominal pain, swelling of ankles, yellowing of the skin or whites of the eyes (jaundice), or unusual bruising or bleeding.
  • This medicine may cause skin reactions. You should let your doctor know if you develop a rash, skin peeling, itching, or other unexplained skin reaction while taking this medicine.
  • There may be a small increased risk of suicidal thoughts and behaviour in people taking antiepileptic medicines such as valproate for any condition. For this reason, it is very important to seek medical advice if you, or someone else taking this medicine, experience any changes in mood, distressing thoughts, or feelings about suicide or self-harm at any point while taking this medicine. For more information speak to your doctor or pharmacist.
  • People with diabetes should be aware that valproic acid may cause false positive results in urine tests for ketones, ie the test may say that ketones are present in the urine even if they are not.
  • If you have epilepsy it is important to take your medication regularly, as directed by your doctor, because missing doses can trigger seizures in some people. If you have trouble remembering to take your medicine you should ask your pharmacist for advice. You may find a pill reminder box helpful.
  • You should not suddenly stop taking this medicine unless your doctor tells you otherwise, as suddenly stopping treatment is likely to make your symptoms return. If this medicine is stopped, it should normally be done gradually, under the supervision of your specialist.

Use with caution in

  • Young children.
  • Decreased kidney function.
  • History of liver disease.
  • Disorders of urea production in the liver (urea cycle disorders).
  • Long-term inflammation of skin and some internal organs (systemic lupus erythematosus).
  • Diabetes.

Not to be used in

  • Active liver disease.
  • Personal or family history of severely decreased liver function, particularly if due to a medicine.
  • Hereditary blood disorders called porphyrias.

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.

  • It is vital that women with epilepsy receive specialist advice before getting pregnant, so they are well informed of potential risks and benefits of continuing antiepileptic treatment. Pregnant women taking antiepileptic medicine have a higher risk of carrying a baby with developmental problems and malformations. However, if a woman with epilepsy stops treatment because she is pregnant, there is a risk of seizures that can harm both mother and baby.
  • Women who decide to try for a baby while taking valproate should start taking folic acid daily as soon as contraception is stopped, as this may reduce the risk of neural tube defects such as spina bifida in the baby. Ask your doctor for advice on the dose to take - it may be recommended that you take 5mg daily.
  • Women who continue to take valproate during a pregnancy should, wherever possible, be prescribed valproate on its own, in the lowest effective dose, in doses that are split over the day, and if possible as a prolonged release brand. These measures can help minimise the risk to the baby. Specialist medical advice must be sought.
  • Valproate passes into breast milk in small amounts, but there have been no reports of harmful effects from this on nursing infants. Seek further medical advice from your doctor.

Label warnings

  • This medication is to be swallowed whole, not chewed.
  • Do not stop taking this medication except on your doctor's advice.

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.

  • Disturbances of the gut such as diarrhoea, nausea, vomiting or abdominal pain.
  • Increased appetite and weight gain.
  • Decrease in the number of platelets in the blood (thrombocytopenia).
  • Temporary hair loss - regrowth may be curly.
  • Increased alertness.
  • Aggression.
  • Hyperactivity.
  • Shaky movements and unsteady walk (ataxia).
  • Tremor.
  • Inflammation of blood vessels (vasculitis).
  • Drowsiness.
  • Confusion.
  • Liver disorders.
  • Irregular or stopping of menstrual periods.
  • Skin rashes.
  • Decreased numbers of white blood cells in the blood (leucopenia).
  • Anaemia.
  • Acne.
  • Increased hair growth (hirsutism).
  • Inflammation of the pancreas (pancreatitis).

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 you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to ensure that the combination is safe.

Valproic acid may increase the blood levels of the following medicines. As this could increase the risk of their side effects, your doctor may need to reduce the dose of these medicines if you taken them in combination with valproic acid:

  • benzodiazepines such as lorazepam
  • bupropion
  • lamotrigine (valproic acid may also increase the risk of skin reactions associated with lamotrigine)
  • phenobarbital
  • phenytoin (phenytoin blood levels should be monitored if taken with valproic acid)
  • primidone
  • tricyclic antidepressants such as amitriptyline and nortriptyline
  • zidovudine.

There may be increased drowsiness and sedation if valproic acid is taken with benzodiazepines, eg diazepam.

There may be an increased risk of side effects on the liver if valproic acid is taken with phenytoin or carbamazepine.

There may be an increased chance of side effects such as dizziness, tiredness, blurred vision and vomiting if valproic acid is taken with carbamazepine.

The following medicines may increase the blood level of valproic acid:

  • cimetidine
  • felbamate
  • large repeated doses of aspirin.

The following medicines may decrease the blood level of valproic acid:

  • carbamazepine
  • phenytoin
  • phenobarbital
  • primidone.

Colestyramine may reduce the absorption of valproic acid from the gut. This can be minimised by separating doses of these medicines by at least three hours.

It is recommended that people who are taking any antiepileptic medicines should avoid taking the herbal remedy St John's wort (Hypericum perforatum). This is because St John's wort may affect the level of antiepileptic medicines in the blood and could increase the risk of seizures.

There may be an increased risk of a drop in white blood cell count if olanzapine is taken valproic acid. If you are taking olanzapine in combination with valproic acid it is important to tell your doctor if you experience any of the following symptoms: sore throat, mouth ulcers, high temperature (fever), or general illness or infection. Your doctor may want to take a blood test to check your blood cells.

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that contain valproic acid as the active ingredient.