Mechanism of action of carbamazepine

As described above, the cause of the seizures is abnormal electrical discharges in the brain. The basis for this is formed by electrically charged particles, so-called ions, which can enter and leave the nerve cells. Carbamazepine works by blocking ion channels, which are the entrances and exits for ions.

In this case, these are specifically channels for sodium. As a result of this closure, nerve cells lose the ability to discharge electrically, often one after the other, and thus trigger or promote an epileptic seizure. Carbamazepine works particularly well in “focal” seizures.

Focal means that the causative discharges are localised to a specific area of the brain and do not spread to the whole brain. Carbamazepine also works well in people where the discharges start at the focal point and only then spread to the whole brain. However, the above-mentioned absences are not affected.

Carbamazepine has a positive effect on epilepsy and also on mood. It is usually taken as a tablet 2 times a day. The exact amount can vary between about 150 and 1000 mg – it has to be tried out individually at which lowest possible amount the seizures disappear.

For this purpose, a small dose is started. It is then gradually increased. If the side effects become too severe before the required dose is reached – which is often the case – alternative drugs such as oxcarbazepine or lamotrigine can be tested.

Side effects

Common side effects that occur at the beginning of the intake, but usually disappear later, are dizziness, a sometimes strong tiredness and a drop in the number of white blood cells, the body’s defense cells. The lack of such defence cells can lead to patients contracting infectious diseases more frequently. Furthermore, double vision and headaches may occur.

The body’s salt balance – and especially the sodium content – can be disturbed, sometimes causing more water to be stored in the body and thus weight gain. In contrast to the side effects mentioned above, a skin rash and inflammation of the liver due to an allergic reaction can occur regardless of the dose taken. Very rare but possible side effects are also psychological changes such as depressive moods, anxiety disorders or aggressiveness.

During the first trimester of pregnancy carbamazepine should be taken only if there is no alternative treatment. Carbamazepine may cause organ malformations in the child, although these are mainly minor. The risk of such malformations can be reduced by eating a folic acid diet and taking folic acid tablets.

However, increased folic acid intake must be started 6 months before pregnancy. After the first third of pregnancy, vitamin K should be taken in addition, as carbamazepine can cause a vitamin K deficiency in the child. In addition to the side effects, carbamazepine also interacts with many medications and can reduce or increase their function. Therefore, the simultaneous use of other medications should be discussed in detail with the doctor.