The active ingredient quetiapine belongs to the group of drugs known as antipsychotic drugs. These drugs are used to treat mental illnesses such as schizophrenia or certain forms of depression. In the past, the term “neuroleptics” (drugs that calm the nerves) was often used, but “antipsychotics” better describes the effect of the drugs.
What is quetiapine?
Quetiapine is a so-called atypical antipsychotic and is used, among other things, in the treatment of psychosis. This is the name given to mental disorders in which there are changes in the experience of the environment, the self, or reality – examples include schizophrenia or manic depression. The main differences from so-called typical or classical antipsychotics are an extended spectrum of action and various side effects.
How does quetiapine work?
Quetiapine (also known by trade names such as Seroquel, Quentiax, or Quetiapinzentiva) binds to various receptors of nerve messengers in the brain: thus, it acts as an antagonist to the messengers dopamine and serotonin, which are involved in the processing and perception of sensory impressions. As a result, quetiapine can help relieve symptoms such as hallucinations and delusions, as well as anxiety, agitation, and depressed mood.
Quetiapine for schizophrenia and depression
In addition to treating schizophrenia, quetiapine can be used to treat so-called bipolar depression. This form of depression is characterized by the occurrence of manic episodes in addition to depressive phases. Such episodes are manifested, for example, by symptoms such as delusions of grandeur, euphoria and loss of social inhibitions. In unipolar depression – that is, when no manic episodes occur – quetiapine is usually prescribed only in addition to other antidepressants.
Quetiapine as a sleep aid?
Quetiapine additionally acts as an antagonist of the neurotransmitter histamine. As a result, it has a sedative, sleep-inducing effect and, unlike some sleep medications, does not carry a risk of dependence. For this reason, it is occasionally prescribed in low doses (about 25 mg) for the treatment of sleep disorders, although it is not approved for this purpose by the authorities in Germany (so-called off-label use). In this case, the physician must inform the patient extensively about possible consequences and bears the liability risk for the treatment.
Weight gain due to quetiapine
Quetiapine can negatively affect metabolism: for example, weight gain may occur during treatment, as well as an increase in blood glucose levels and blood lipid levels. Less commonly, diabetes mellitus (diabetes) may develop. In addition, quetiapine may increase appetite.
What side effects may occur?
In addition to affecting metabolism, the following side effects may occur with the use of quetiapine:
- Headache, drowsiness, dizziness
- Drowsiness
- Low blood pressure, circulatory problems
- Dry mouth
- Nausea, vomiting
- Diarrhea or constipation
- Fast or irregular heartbeat, cardiac arrhythmia.
- Parkinson’s-like symptoms: Tremors, stiffness, slowed mobility.
- Motor function disorders, uncontrollable muscle movements.
- Convulsions and seizures
- Change in various blood values
For a complete list of possible side effects, please read the package insert for your medication.
Quetiapine drug interactions
Quetiapine is broken down by a certain enzyme in the liver and therefore should not be taken with substances that inhibit this enzyme, otherwise it may cause a large increase in the level of the drug in the blood. These include:
- Certain drugs against HIV
- Some drugs against fungal infections
- Some antibiotics such as clarithromycin and erythromycin
- Grapefruit juice
In addition, interactions may occur if certain sedatives are taken at the same time and if alcohol is consumed. Other possible interactions can be found in the package insert.
Dosage individually different
Quetiapine comes in different dosages as well as retard tablets (for example, Seroquel prolong). The dosage depends on various factors such as age, type of disease, and previous illnesses and is determined by the doctor.In principle, treatment should be started gradually – i.e. with a low dosage – and slowly increased. Usual dosages are 50 mg or 100 mg up to a maximum of 800 mg. For use in children and adolescents, there is not yet sufficient experience.
How quickly and for how long does quetiapine work?
How quickly quetiapine takes effect varies from individual to individual: it may take several hours to several weeks for a sufficient level of active substance to be reached in the blood and for the full effect to develop. 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 stopped abruptly but phased out slowly. This is because if discontinuation is too rapid, withdrawal-like symptoms such as insomnia, nausea, headache, diarrhea, vomiting, dizziness, or irritability may occur. Therefore, the dose should be gradually reduced over one to two weeks. Please follow your doctor’s instructions in this regard.
Quetiapine in pregnancy and lactation.
Because safety has not yet been established in studies, quetiapine should be prescribed during pregnancy and lactation only after careful consideration of the benefits and risks. In general, treatment with quetiapine during the first three months of pregnancy appears to be less risky than toward the end of pregnancy. In any case, pregnancy should be carefully monitored by close follow-up.
What are the alternatives?
In addition to various other atypical antipsychotics such as olanzapine or risperidone, agents from the group of typical antipsychotics can also be used for schizophrenia. These include haloperidol or melperone, for example. These substances usually have a strong antipsychotic effect, but hardly any effect against depressive symptoms. In addition, the side effect profile differs: typical antipsychotics cause motor disturbances and Parkinson’s-like symptoms more frequently than quetiapine. However, they affect metabolism less and weight gain occurs less frequently.
Alternative antidepressants
There are very many antidepressant medications that can be classified into different groups. Agents commonly used for depression include venlafaxine, citalopram, mirtazapine, and sertraline. An alternative to quetiapine for bipolar depression is the mood-stabilizing agent lithium.
