Carbamazepine is an anticonvulsant and mood-stabilizing drug , used in the treatment of bipolar disorder and to control seizures.
In this article we will know the main characteristics of this drug, its uses in therapy and indications, as well as explaining its side effects and contraindications.
Carbamazepine: general characteristics
Carbamazepine is a drug in the class of classical antiepileptic drugs . It is marketed under several names: Carbamazepine EFG, Carbatrol, Equetrol, Tegretal, and Tegretol. At present its mechanism of action is not entirely known, but it is known to act on sodium channels.
This drug is used to treat partial seizures. It is also used as an alternative to lithium salts in bipolar disorder, and in patients with manic seizures who are resistant to antipsychotics.
Carbamazepine is considered u not of the reference drugs among anticonvulsants, after phenobarbital .
Mechanism of action
Its mechanism of action is not yet known exactly. It is known that stabilises neuronal membranes that are in a state of hyperexcitation, prevents repeated shocks to neurons and reduces the synaptic spread of the nerve impulse.
To prevent repeated discharges, carbamazepine blocks the voltage-dependent sodium channels in depolarized neurons . In this way, it manages to intervene selectively on those neurons that are having an epileptic discharge. This is the main mechanism of action of this drug and the reason for its anticonvulsant capacity.
In addition, it appears to affect NMDA receptors and the flow of calcium across the neuron membrane. It reduces the release of glutamate and stabilizes the neuronal membranes , which explains its antiepileptic capacity.
In relation to its ability to treat the manic crises of bipolar disorder, it appears to depress the turnover of dopamine and noradrenaline.
Carbamazepine is given only orally in tablet form. Its absorption is slow and irregular, and it should be taken with food in the stomach, as the digestion of food aids in its absorption.
Indications: in which disorders is it used?
This drug is indicated for the treatment of epilepsy , especially for epileptic seizures with simple or complex symptoms, regardless of whether there is loss of consciousness or not. It is also used for tonic-clonic epilepsy.
It has been used to treat pain associated with end-stage neuralgia . It is important to note that it is not an analgesic drug and therefore its use is not recommended to treat common pains.
It is also sometimes used as a prophylactic substance for mania in bipolar disorder .
Carbamazepine is suitable for both monotherapy, i.e. using this drug only, and combination therapy. In any case, its use and mode of use depends on the indications of the medical team that has evaluated the specific case in a personalized manner.
Use in epilepsy
Whenever possible, carbamazepine should be used as monotherapy. The treatment starts with low doses and gradually increases them until the therapeutic effect is achieved . It is recommended that plasma levels be determined in order to establish the correct dosage.
If epilepsy has been treated with another drug in the past, carbamazepine should be introduced gradually, maintaining the dose of the previous drug and regulating it progressively.
The administration of this drug varies depending on the age group . In children under 4 years of age, the recommended dose at the beginning of treatment is 20 to 60 mg per day, increasing every two days. For those over 4 years of age, treatment can be started with 100 mg a day, increasing the dose by 100 mg every week.
In adults, start with 100 to 200 mg, once or twice a day. Little by little the doses are increased, generally reaching 400 mg two or three times a day. There are cases of patients who reach doses of 1600 mg a day in order to have a therapeutic response.
This drug may involve the following adverse reactions, most of them when too high a dose of carbamazepine has been given: dizziness, ataxia, drowsiness, headache, fatigue, accommodation disorders, skin problems such as allergies and hives, nausea, vomiting, dry mouth, weight gain, hyponatremia, gastrointestinal problems.
It should be noted that an overdose may result in death . In the event that the patient has been given too high a dose, the stomach should be pumped and haemoperfused, depending on the severity.
The use of this drug is not recommended in people who have hypersensitivity to structurally related drugs, such as tricyclic antidepressants. It is also not indicated in patients who have suffered from bone marrow depression, atrioventricular block and liver porphyrias .
Carbamazepine should not be combined with monoamine oxidase inhibitors (MAOIs), and if the patient has been treated with MAOIs, it is recommended to wait at least two weeks after treatment has ended.
Special precautions for use
Like any other psychoactive drug, carbamazepine must be prescribed under medical supervision .
Special care should be taken in patients with a history of liver, kidney and heart problems. Also if there have been adverse hematological reactions to other drugs or there have been interrupted periods of treatment with this drug. It should be assessed whether the risks are less than the benefit.
1. Hematological effects
This drug has been associated with cases of agranulocytosis and aplastic anemia . There may be a temporary decrease in platelets, although it is not common for it to go away and cause blood problems. However, before and during treatment, blood tests are recommended.
If there are bone marrow problems, treatment is usually stopped.
2. Severe dermatological reactions
Treatment with carbamazepine has been associated with the development of severe, sometimes fatal, skin problems such as toxic epidermal necrolysis and Stevens-Johnson syndrome . This type of reaction occurs between 1 and 6 out of every 10,000 people treated in Caucasian populations, and this risk is ten times higher in Asian populations.
We will now discuss why there is a difference between these two populations.
2.1. Allele HLA-B 1502
This allele is common in Asian populations, especially in China and Thailand . It can imply dermatological problems when treated with carbamazepine.
For this reason, it is recommended that before starting treatment, Asian people should undergo a gene analysis to ensure that the treatment will not cause them this type of problem.
2.2. Allele HLA 3101
This other allele has also been associated with severe dermatological reactions to carbamazepine .
However, unlike the previous one, this allele is present in Caucasian and Japanese populations, and is not common. However, there is still not enough evidence that this allele is actually involved in dermatological problems in these populations.
- Vademecum. (2016). Carbamazepine.
- Adam, A. and Prat, G. (2016). Psychopharmacology: Mechanism of action, effect and therapeutic management. Barcelona, Spain. Marge Medica Books.