Your doctor will almost certainly prescribe one of these before trying any other medication. Each has some individual side-effects inEdit addition to those already mentioned which are common to all the drugs, but only a small proportion of people develop these individual side-effects. You will see that the drug you take has two or even more names. The first name given here is the drug’s chemical name. The name (or names) given in brackets is its trade name — the drug manufacturer’s ‘own-brand’ version of the drug. Sometimes several drug companies produce their own version of a drug. Usually there is no difference between any of these brands, but it is usually best to stick to one version of a drug if you have found that it suits you.
Whatever drug you are given, you will probably be prescribed a small dose to start with, which will gradually be increased if you suffer no side-effects.
CARBAMAZEPINE (TEGRETOL)
Carbamazepine is one of the best-known and most widely-used anticonvulsants. Most doctors believe that it has the fewest side-effects, and it is thought to be the safest drug for women who are pregnant. So it is the drug your doctor is most likely to try first.
Its main uses are in complex partial seizures and generalized tonic clonic (grand mal) seizures, during pregnancy and in people who are depressed, as it tends to brighten mood.
Probably the best preparation to take is Tegretol Retard – this is a slow-release form of the drug, which means you may need only one dose during each 24 hours, at night.
Possible side-effects
Rash If you develop a rash, your doctor will probably keep you on a low dose of the drug for a while and the chances are that the rash will disappear. A very few people develop a rash so severe that the drug has to be stopped.
A low white blood cell count These cells are the ones which fight infection, and so a low white cell count means that you may be more likely to develop infections. If your white cell count continues to drop your doctor will lower the dose, and some doctors prefer to take patients off the drug. However, my own view is that it
is not necessary to withdraw the drug altogether unless the white count does not rise when the dose of the drug is reduced.
Water retention, sometimes with swollen ankles and puffy face This happens because carbamazepine affects the hormone which controls water excretion by the kidneys. This can result in a low – sometimes a very low – blood sodium level. In your three or six-monthly check up your doctor should always measure your blood sodium level. Usually even if you have a very low sodium level it will come back towards normal if the dose of carbamazepine is slightly reduced. However, occasionally this does not occur and then the drug has to be discontinued.
Blocks the action of the thyroid gland Your thyroid may be tested from time to time to check that this is not happening.
Reduces the action of other drugs This is because carbamazepine causes the liver (which is the organ responsible for breaking down most other drugs) to produce more enzymes and so become more active. If you take the contraceptive pill, for example, it will be broken down more rapidly, and in order for it to be effective you will need to take a higher dose.
Toxic side-effects
(These indicate that the dose you are taking is too high.) Poor balance, double vision and tiredness.
When to avoid
Carbamazepine should not be taken if you have any liver damage, or have responded badly to the drug in the past. Carbamazepine may also be unsuitable if you have some form of heart disease.
PHENYTOIN (EPANUTIN)Phenytoin is a good anticonvulsant, but is a drug which is unpopular at the moment because of its unpleasant side-effects. It is used to control grand mal seizures, and complex partial seizures.
Phenytoin is a drug which is difficult to make up properly. Epanutin is the product of the drug company which was the first to produce this drug. Others have copied them, but not always so successfully. Not long ago, for example, the Australian government decided to save money and recommended the use of cheaper brands of phenytoin. Unfortunately, these different products had different absorption rates, and in consequence many people developed severe seizures. The government finally had to allow the prescription of Epanutin again.
So although there are other, cheaper brands of phenytoin on the market, I would always advise that you stick to Epanutin and make sure that your doctor prescribes it by name.
Possible side-effects
Rashes
Slows you down
Drowsiness
Roughens facial features
Swollen gums
Excessive hairiness
Tingling in fingers and toes (Peripheral neuritis)
Leaches calcium from bones
In high doses, reduces action of other drugs Like Carbamazepine, phenytoin makes the liver more active and produce more enzymes. The contraceptive pill, for example, may be less effective because it is destroyed more rapidly. In this instance you would have to take a stronger dose of the pill to get the full contraceptive effect.
Toxic side-effects
(These indicate that the dose you are taking is too high.) Rapid, jerky eye movements (nystagmus), disturbed balance, tremor. Most importantly, if too high a dose is given, phenytoin stops acting as an anticonvulsant and can actually induce seizures.
Double or blurred vision and headaches sometimes occur and, rarely, phenytoin can cause severe confusion and the inability to think clearly. But these side-effects are rare, and usually only happen in someone who has taken the drug for a very long time. If they do occur, see your doctor who will probably withdraw the drug.
When to avoid
Phenytoin should be avoided if you are pregnant, and not taken if you have any liver damage or suffer from osteoporosis (weakness of the bones).
SODIUM VALPROATE (EPILIM)
This is a useful drug for controlling generalized seizures (both grand mal, and absence seizures) and myoclonic jerks. It is also the drug most often given to prevent febrile convulsions in susceptible children. Sodium valproate has a short half-life (see p.44), so it may need to be taken three times a day to be effective. However, you will probably be given the ‘Epilim Chrono’ form. This is a slow-release preparation which you will probably only need to take once a day (although some patients like to take it twice a day). It is so much more convenient that I no longer prescribe ordinary valproate any more.
Sodium valproate interacts with another commonly prescribed drug, lamotrigine, preventing its breakdown. In effect, this means that too much lamotrigine will accumulate in the blood. So if you are taking both drugs your doctor will want to check your serum level of lamotrigine regularly to make sure it is not too high.
Possible side-effects
Hair loss If you take sodium valproate it is worth looking at your comb after you have combed your hair to see if you seem to be losing more hair than usual. Hair loss is sometimes dose-dependent; as sodium valproate is a good drug, it is usually worth trying a lower dosage before stopping the drug completely. If you do continue with the drug, the hair loss may become so bad that you will need to wear a wig, and when finally you do stop the drug and your hair grows back, it is likely to be of a different colour and finer texture.
Change in colour and texture of hair This is usually associated with hair loss, although it can occur on its own. Again a reduction of drug dosage may help.
Tremor This is a difficult side-effect to treat as it is seldom dose-dependent (although it can be a toxic symptom, due to too high a dose). I have found that if tremor occurs then it is best to withdraw the drug rather than to persevere with lower dosages.
Weight gain This is one of the most difficult side-effects to deal with. Most people are upset when they put on too much weight, and weight gain is particularly distressing for adolescents, who are, even in the best of circumstances, very self-conscious about the way they look. Unfortunately sodium valproate is usually very effective in this age group and very widely used. In my experience, weight gain cannot be avoided simply by reducing the dose of the drug. If it is very troublesome a change of drug is the only satisfactory solution.
Toxic side-effects
(These indicate that the dose you are taking is too high.) Poor balance, double vision, tiredness and tremor. Very occasionally, sodium valproate can have a serious effect on blood clotting. Children given the drug will be watched carefully as, rarely, it can cause liver damage in a very special group of young children.
When to avoid
Sodium valproate should be avoided if possible during pregnancy, or if you have ever had liver damage. It should be taken with care with phenobarbitone or primidone, as the combination can make you very frowsy. If you do become pregnant while taking sodium valproate, you should certainly discuss this with your doctor.
ETHOSUXIMIDE (ZARONTIN)
Ethosuximide is an alternative to sodium valproate as the drug of first choice to control absence seizures (petit mal). Both drugs are probably equally effective, but sodium valproate has the advantage that it controls generalized seizures too, so if you suffer both types of seizure, sodium valproate is probably the drug you will be given.
Possible side-effects
These are few. The most likely are:
Nausea
Dizziness
Headache
Drowsiness
Very rarely adults may also experience hallucinations (seeing things or hearing voices when no one is there) or suffer depression.
When to avoid
Ethosuximide should not be used during pregnancy, if you are breast-feeding or if you have ever had liver or kidney damage.
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