The active ingredient quetiapine belongs to the group of so-called antipsychotic drugs. These medicines are used to treat mental illnesses such as schizophrenia or certain types of depression. In the past, the term "neuroleptics" (nerve-calming medicines) was often used, but "antipsychotics" describes the effect of the medicines better.
What is quetiapine?
Quetiapine is a so-called atypical antipsychotic and is used inter alia in the treatment of psychosis. This is the term used to describe mental disorders that cause changes in the experience of the environment, one's self, or reality - such as schizophrenia or manic depression. Main differences to so-called typical or classical antipsychotics are an extended spectrum of activity as well as various side effects.
How does quetiapine work?
Quetiapine (also known under trade names such as Seroquel®, Quentiax® or Quetiapinzentiva®) binds in the brain to various receptors of neurotransmitters: it acts as an antagonist to the messengers dopamine and serotonin, which participate in the processing and perception of sensory impressions.
As a result, quetiapine can help alleviate symptoms such as hallucinations and delusions, as well as anxiety, arousal and depressive mood.
Quetiapine in schizophrenia and depression
In addition to treating schizophrenia, quetiapine can be used in bipolar depression. This form of depression is characterized by the occurrence of manic episodes in addition to depressive phases. Such episodes are expressed, for example, by symptoms such as megalomania, euphoria and loss of social inhibitions.
In unipolar depression - when no manic phases occur - quetiapine is usually only prescribed in addition to other antidepressants.
Quetiapine as a sleep aid?
Quetiapine also acts as an antagonist of the messenger histamine. As a result, it has a calming, sleep-promoting effect and unlike some sleeping pills, it does not pose a risk of dependency.
Therefore, it is occasionally prescribed in low dosage (about 25 mg) for the treatment of sleep disorders, although it is not approved in Germany for this purpose by the authorities (so-called off-label use).
The doctor must inform the patient in this case extensively about possible consequences and bears the liability risk for the treatment.
Weight gain due to quetiapine
Quetiapine can have a negative impact on the metabolism: it may lead to an increase in weight during treatment as well as an increase in blood sugar and blood lipid levels.
Less commonly, diabetes mellitus can develop. In addition, quetiapine can be appetite-promoting.
What side effects can occur?
In addition to interfering with the metabolism, the following side effects may occur with the use of quetiapine:
- Headache, drowsiness, dizziness
- low blood pressure, circulatory problems
- dry mouth
- Nausea, vomiting
- Diarrhea or constipation
- fast or irregular heartbeat, arrhythmia
- Parkinson-like symptoms: tremor, stiffness, slowed mobility
- Motor disorders, uncontrollable muscle movements
- Convulsions and seizures
- Change of different blood values
For a full list of possible side effects, read the package insert of your medication.
Interactions of quetiapine
Quetiapine is broken down by a specific enzyme in the liver and must therefore not be taken with substances that inhibit this enzyme, otherwise it can lead to a strong increase in drug levels in the blood.
These include, among others:
- certain medicines for HIV
- some remedies for fungal infections
- some antibiotics like clarithromycin and erythromycin
- grapefruit juice
In addition, interactions may occur with the concomitant use of certain sedatives and with alcohol consumption. Other possible interactions can be found in the package leaflet.
Dosage individually different
Quetiapine is available in different dosages as well as sustained-release tablets (for example Seroquel prolong®). The dosage depends on various factors such as age, type of disease and pre-existing conditions and is determined by the doctor.
In principle, the treatment should be started gradually - ie with a low dosage - and slowly increased. Dosages of 50 mg or 100 mg, usually up to a maximum of 800 mg, are usual here. For use in children and adolescents, there is still insufficient experience.
How fast and how long does quetiapine work?
How fast quetiapine works is individually different: It can take several hours to several weeks until a sufficient drug level in the blood is reached and the full effect unfolds. The duration of action is about twelve hours, so quetiapine is usually taken twice a day.
What should be considered when discontinuing?
When quetiapine therapy is discontinued, the drug should not be discontinued abruptly, but should be swabbed out slowly. For too fast a withdrawal can occur withdrawal-like symptoms such as insomnia, nausea, headache, diarrhea, vomiting, dizziness or irritability. Therefore, the dose should be gradually reduced over one to two weeks. Please follow the instructions of your doctor.
Quetiapine in pregnancy and lactation
Since the safety in studies could not be proven, quetiapine should be prescribed during pregnancy and lactation only after careful consideration of benefits and risks.
In general, treatment with quetiapine in the first three months of pregnancy seems to be less risky than towards the end of pregnancy. In any case, pregnancy should be carefully monitored through close monitoring.
Which alternatives are there?
In addition to various other atypical antipsychotics such as olanzapine or risperidone, drugs from the group of typical antipsychotics can also be used in schizophrenia. These include, for example, haloperidol or melperone.
These substances usually have a strong antipsychotic effect but hardly any depressive symptoms. In addition, the side effect profile differs: typical antipsychotics cause motor disorders and Parkinson-like symptoms more often than quetiapine. However, they affect the metabolism less and it is less likely to gain weight.
There are many antidepressant medications that can be divided into different groups. Commonly used in depression drugs include venlafaxine, citalopram, mirtazapine and sertraline. An alternative to quetiapine in bipolar depression is the mood-stabilizing agent lithium.