How chlorprothixene works
Chlorprothixene helps against psychotic symptoms such as hallucinations and delusions (antipsychotic effect). It also has a depressant effect, counteracts nausea and vomiting (antiemetic), and makes it easier to fall asleep.
Chlorprothixene mediates its main effect by binding to and blocking docking sites of the endogenous neurotransmitter dopamine (dopamine receptors).
Dopamine receptors are also located in the so-called chemoreceptor trigger zone, a part of the vomiting center in the brain. Their blockade by chlorprothixene prevents nausea and vomiting.
In addition, chlorprothixene blocks other receptors in the body. This triggers other effects:
Chlorprothiazine also inhibits histamine receptors. Among other things, histamine plays a role in the sleep-wake rhythm and promotes wakefulness. In addition, the neurotransmitter triggers vomiting by binding to receptors in the vomiting center of the brain. Chlorprothixene inhibits these effects by blocking the receptors. Thus, it exerts a sleep-promoting and strong sedative and antiemetic effect.
Adrenaline and noradrenaline usually bind to alpha-1 adrenoceptors. One of the consequences of this is that the blood vessels constrict. If chlorprothixene inhibits these receptors, the vessels dilate. This can cause low blood pressure, for example.
Chlorprothixene: Onset and duration of action
The duration of action is several hours. It takes between eight and twelve hours for half of the active substance to leave the body again (so-called half-life).
What are the side effects of chlorprothixene?
Extrapyramidal motor disturbances are possible, especially with high doses of chlorprothixene. In children, however, lower doses of active ingredient are usually sufficient for this side effect to occur.
Patients often suffer side effects from the depressant effect of chlorprothixene: They feel tired and dizzy, have headaches or react more slowly.
Sometimes it also happens that patients sleep worse or are nervous.
Chlorprothixene inhibits the action of the neurotransmitter acetylcholine. Possible consequences are so-called anticholinergic side effects: For example, those affected have a dry mouth, blurred vision or suffer from constipation.
Frequently, patients report increased appetite and weight gain during therapy with chlorprothixene. Occasionally, patients’ appetite also decreases and they lose weight during therapy.
These effects on fertility subside after chlorprothixene therapy is stopped.
Rarely, chlorprothixene alters the conduction of impulses in the heart muscle and prolongs the so-called QT time (a time interval in the ECG). This increases the risk of life-threatening cardiac arrhythmias. This is especially true for patients with pre-existing heart conditions. For this reason, physicians usually perform an ECG examination on their patients before starting chlorprothixene therapy.
For additional information on possible side effects, see the package leaflet that came with your chlorprothixene medicine. Contact your doctor or pharmacist if you notice or suspect any other side effects.
When is chlorprothixene used?
Chlorprothixene is approved to treat psychomotor agitation and agitation in patients with mental illnesses such as schizophrenia.
In Switzerland, chlorprothixene is also approved for other diseases:
- against anxiety, restlessness and aggressiveness in patients who are addicted to alcohol or undergoing withdrawal treatment
- as supportive therapy against agitation or anxiety in depressive syndromes, anxiety disorders or phobias
- for the treatment of severe behavioral disorders in congenital or early acquired developmental disorders
- for severe chronic pain in combination with painkillers
Sometimes mentally ill patients are given chlorprothixene to sleep if they suffer from insomnia. However, the use of chlorprothixene as a sleep aid is not an approved indication. It is therefore used off-label.
How chlorprothixene is used
Doctors determine the chlorprothixene dosage for each patient individually. The severity of the illness and how well the patient responds to the drug play a role.
Chlorprothixene has only a weak antipsychotic effect. For this reason, physicians often combine the active ingredient with other medications.
Chloprothixene tablets are taken unchewed with some liquid. As a rule, doctors prescribe a total daily dose, which is to be taken in several individual doses per day.
Because chlorprothixene often makes you sleepy, the first dose should ideally be taken in the evening. For the same reason, it is advisable to take a larger portion of the active ingredient in the evening for higher total daily doses. This helps to prevent more severe drowsiness during the day.
Dosages of chlorprothixene preparations in Germany and Austria:
Adult patients take 15 to 100 milligrams of chlorprothixene for mild to moderate agitation. In severe cases and in manic disorders, affected individuals receive 100 to 400 milligrams daily. Patients receiving daily doses of more than 150 milligrams of chlorprothixene are usually hospitalized.
Dosages of chlorprothixene preparations in Switzerland:
Patients with schizophrenia, mania or other psychoses take 50 to 100 milligrams of chlorprothixene at the beginning. The doctor gradually increases the dose until the symptoms are sufficiently relieved. Usually, 300 milligrams of chlorprothixene is sufficient. In severe cases, patients receive up to 1200 milligrams of chlorprothixene.
Alcoholics as well as patients during withdrawal receive 500 milligrams of chlorprothixene per day, divided into several single doses. If the symptoms of withdrawal improve, the doctor reduces the dose. To reduce the risk of relapse, doctors sometimes administer another smaller amount of chlorprothixene as maintenance therapy.
Pain patients receive an individualized chlorprothixene dose determined by the physician in combination with pain medications.
Lower dosages for specific patient groups.
Children and adolescents take appropriately lower doses. Read more in the section “Chlorprothixene in children”.
Patients with impaired liver or kidney function are also usually prescribed a reduced dose.
Discontinuation of the chlorprothixene drug
If you suddenly stop taking chlorprothixene, your body may react with discontinuation symptoms:
Patients often feel nauseous, sweat more, or have sensory disturbances (e.g., a tingling or numb feeling on the skin). In addition, patients may sleep more poorly, tremble, or have increased anxiety.
However, it is better to avoid such symptoms from the outset. This can be achieved by “phasing out” the therapy. This means that the drug is not discontinued abruptly, but the dose is reduced gradually – as recommended by the treating physician. In this way, the body is slowly weaned off chlorprothixene and discontinuation symptoms are avoided.
Further important information on chlorprothixene
Misuse
People who take chlorprothixene even though there is no medical reason for doing so often feel tired, in a bad mood, or listless. If taken for too long or in high doses, there is also a risk of serious side effects that may not go away.
Overdose
If patients take too high a dose of chlorprothixene, they are usually dizzy, confused, or have blurred vision. The heart beats irregularly, and the risk of severe arrhythmias and even cardiovascular failure increases.
In addition, a chloprothixene overdose may cause movement disorders or tongue spasms (extrapyramidal motor disorders – see “Side effects”).
If you suspect an overdose of chlorprothixene, call an emergency physician immediately. Severe poisoning with the active ingredient may cause cardiovascular failure, coma or respiratory arrest!
Medical professionals treat affected people in the hospital depending on the severity of the overdose. They may administer activated charcoal. This binds the active ingredient in the digestive tract so that it cannot pass into the blood.
When should chlorprothixene not be used?
Chlorprothixene medication should not be used under the following circumstances:
- if you are hypersensitive to the active substance, other thioxanthene active substances or other components of the medicine
- if you suffer from impaired consciousness, for example acute intoxication by alcohol, opioid painkillers or other depressant psychotropic drugs
- in case of circulatory collapse or coma-like state
- in case of disturbances of the magnesium or potassium balance
- during pregnancy and lactation
- in children under three years of age
- in case of simultaneous use of drugs that prolong the QT time
For some pre-existing conditions, physicians carefully consider whether to prescribe chlorprothixene. These include, for example:
- severe liver and kidney dysfunction
- very low blood pressure (chlorprothixene further reduces blood pressure)
- Parkinson’s disease
- History of epilepsy and seizures (chlorprothixene lowers seizure threshold)
- Hyperthyroidism (patients need appropriate therapy for thyroid disease before taking chlorprothixene)
- constricted bowel or urinary tract
- glaucoma
- Myasthenia gravis (autoimmune disease in which the transmission of nerve signals is disturbed)
These drug interactions may occur with chlorprothixene
If you take other agents that prolong the QT interval in addition to chlorprothixene, the risk of cardiac arrhythmias increases. Such agents include:
- Antibiotics from the macrolide group (e.g., erythromycin) or fluoroquinolones (e.g., moxifloxacin).
- Medicines to treat heart rhythm disorders (antiarrhythmics) such as amiodarone
- Medicines to treat depression (antidepressants) such as citalopram
A specific enzyme system in the liver (CYP2D6 system) degrades chlorprothixene. Some drugs can affect the activity of this enzyme system and thus the degradation of the antipsychotic:
CYP inducers increase the activity of the enzyme system and thus the degradation of chlorprothixene. The dose may then no longer be sufficient for a sufficient effect. CYP inducers include the antibiotics doxycycline and rifampicin (used to treat tuberculosis). However, cigarette smoke also accelerates the degrading enzyme.
- Antihypertensive agents increase the antihypertensive effect of chlorprothixene. Affected persons are dizzy and tend to fall (especially elderly people and people with gait problems).
- Drugs against the neurotransmitter acetylcholine increase the anticholinergic side effects of chlorprothixene (such as dry mouth).
- Dopamine antagonists increase the dopamine-inhibitory effects of chlorprothixene. This promotes extrapyramidal motor side effects (such as movement disorders).
Refrain from alcohol during chlorprothixene therapy!
If you take the active substance with tea or coffee, its effect may be reduced. Therefore, ideally swallow the tablets with a glass of water.
Chlorprothixene may interact with anticoagulant medications. In this case, the doctor may check the patient’s blood clotting more frequently.
Chlorprothixene in children: What should be considered?
Children under the age of three should not take chlorprothixene.
In older children, the dose of active ingredient depends on the child’s weight. Usually, children three years and older take 0.5 to one milligram of chlorprothixene per kilogram of body weight. The total daily dose is divided into two individual doses.
Chlorprothixene during pregnancy and breastfeeding
If a pregnant patient receives chlorprothixene in the first trimester of pregnancy, the doctor may recommend additional ultrasound examinations. In this way, he checks whether the unborn child is developing normally.
The active ingredient passes into breast milk. According to experts, however, breastfeeding can continue with reservations if the mother takes chlorprothixene as the only medication. It is important to observe the child closely in order to recognize possible side effects quickly. If the child is particularly restless, dizzy or drinking worse, parents should immediately inform a pediatrician.
