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How does it work?
Neurontin capsules and tablets contain the active ingredient gabapentin, which is a medicine that is mainly used to treat epilepsy. (NB Gabapentin is also available without a brand name, ie as the generic medicine.) Gabapentin works by stabilising electrical activity in the brain.
The way in which gabapentin works is not fully understood. It is thought to work by binding to calcium channels found on nerve cells in the brain and spinal cord. This is thought to affect the release of various neurotransmitters from these nerve cells.
Neurotransmitters are natural body chemicals that are stored in nerve cells. They are involved in transmitting messages between the nerve cells. Gabapentin is thought to reduce the release of a neurotransmitter called glutamate.
Glutamate is a neurotransmitter that acts as a natural 'nerve-exciting' agent. It is released when electrical signals build up in nerve cells and subsequently excites more nerve cells. It is thought to play a key role in causing epileptic seizures. Reducing the release of glutamate from the nerve cells in the brain is thought to help stabilise the electrical activity in the brain and prevent epileptic fits.
Gabapentin is used to prevent partial seizures, and partial seizures that spread to secondary generalised seizures.
Glutamate is also involved in transmitting pain signals in the brain and nervous system. As gabapentin reduces the release of this neurotransmitter it can also be used to treat nerve pain occuring as a result of damage to or a disturbance in the function of nerves (neuropathic pain). It probably works in other ways in this area as well.
What is it used for?
- Epilepsy - used for partial seizures with or without secondary generalisation. This medicine may be used on its own to treat adults and children aged 12 years and over, or as an add-on therapy for adults and children aged six years and over who are already taking other antiepileptics.
- Peripheral nerve pain (neuropathic pain) in adults, for example due to diabetic neuropathy or following shingles (post-herpetic neuralgia).
- Preventing migraine (unlicensed use).
How do I take it?
- Gabapentin can be taken either with or without food.
- The dose prescribed depends on the individual, the condition being treated and how well it is controlled. Your dose will be increased gradually to begin with. Follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the medicine. Try to space your doses evenly over the day.
- 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 without consulting your doctor, as this may result in your seizures or nerve pain returning or getting worse, or side effects such as anxiety, nausea, pain, sweating or difficulty sleeping. If it is decided that you should stop taking this medicine, the dose should usually be reduced gradually over at least a week. Follow the instructions given by your doctor.
- This medicine might make you feel dizzy or sleepy and so may reduce 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. If you feel sleepy while taking this medicine this could be made worse by drinking alcohol.
- This medicine may sometimes cause severe skin reactions. You should let your doctor know straight away if you develop a fever, swollen glands, 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 gabapentin 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.
Use with caution in
- People over 65 years of age.
- Children and adolescents (the effects of long-term gabapentin therapy (greater than 36 weeks) on learning, intelligence and development in children and adolescents have not been adequately studied).
- People with decreased kidney function.
- Diabetes (this medicine may cause fluctuations in blood sugar).
- This medicine is not generally considered effective in the treatment of absence seizures and may aggravate them in some people. It should be used with caution in people with mixed seizures that include absences.
Not to be used in
- People with known sensitivity or allergy to any ingredient.
- Neurontin capsules contain lactose and should not be taken by people with rare hereditary problems of galactose intolerance, the Lapp lactase deficiency or glucose-galactose malabsorption. Neurontin tablets do not contain lactose.
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 very important for women with epilepsy to talk to the doctor responsible for their epilepsy treatment before becoming pregnant. Antiepileptic medicines in general are associated with an increased risk of developmental disorders and malformations in the baby. However, stopping antiepileptic treatment during pregnancy runs the risk of the mother having seizures, which can harm both the mother and the foetus. This risk may be higher than that from continuing the medication. It is important that all the risks and benefits of treatment are weighed up. Seek medical advice from your doctor.
- The safety of gabapentin for use during pregnancy has not been established. It is not recommended for use in pregnancy unless the benefits to the mother outweigh the risks to the unborn baby. Seek medical advice from your doctor.
- This medicine passes into breast milk, but the effect of this on a nursing infant is unknown. It should only be taken by mothers who are breastfeeding if the benefits to the mother outweigh any risks to the nursing infant. Seek medical advice from your doctor.
- Do not take indigestion remedies at the same time of day as this medication.
- This medication may cause drowsiness. If affected do not drive or operate machinery.
- Do not stop taking this medication except on your doctor's advice.
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.
Very common (affect more than 1 in 10 people)
- Sleepiness or fatigue.
- Shaky movements and unsteady walk (ataxia).
- Viral infections.
Common (affect between 1 in 10 and 1 in 100 people)
- Infections, such as urinary tract or airway infections.
- Decrease in the number of white blood cells in the blood (leucopenia).
- Changes in appetite.
- Unstable moods (emotional lability).
- Confusion, loss of memory (amnesia).
- Anxiety or nervousness.
- Difficulty sleeping (insomnia).
- Tremor or twitching.
- Speech problems.
- Problems with coordination.
- Changes in sensation, for example pins and needles or numb sensations.
- Visual disturbances, such as double vision.
- Spinning sensation (vertigo).
- Raised blood pressure (hypertension).
- Shortness of breath, cough.
- Gut disturbances such as dry mouth, indigestion, nausea, vomiting, constipation, diarrhoea or abdominal pain.
- Small haemorrhage (bleeding) in the skin (purpura), often seen as bruises.
- Skin reactions such as rash, itching or acne.
- Facial swelling.
- Swelling of the legs, ankles or face due to excess fluid retention (oedema).
- Pain in the back, muscles or joints.
- Feeling weak or generally unwell.
- Weight gain.
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 make sure that the combination is safe.
Indigestion remedies (antacids) containing aluminium or magnesium may reduce the absorption of gabapentin from the gut. Indigestion remedies should therefore not be taken at the same time as a dose of gabapentin, or in the two hours before a dose.
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.
This medicine is not known to interact significantly with other medicines. However, if it makes you feel sleepy or dizzy, this effect is likely to be increased if you take it in combination with other medicines that can cause drowsiness, in particular morphine, or with alcohol. If you are prescribed morphine in combination with gabapentin you should let your doctor know if it makes you feel sleepy, or if any drowsiness gets worse.
This medicine does not affect hormonal contraceptives such as the pill.
Other medicines containing the same active ingredient
Gabapentin tablets and capsules are also available without a brand name, ie as the generic medicine.