The active substance thioridazine represents a neuroleptic. It can be used to treat schizophrenia and other mental illnesses.
What is thioridazine?
The active substance thioridazine represents a neuroleptic. It can be used to treat schizophrenia and other mental illnesses. The antipsychotic thioridazine is part of the group of active substances known as neuroleptics. From a chemical point of view, it belongs to the phenothiazines and is used as a low-potency neuroleptic. Thioridazine is used for the treatment of chronic forms of schizophrenia and other psychoses associated with agitation and psychomotor agitation. As a rule, however, the drug is only used when other medications have not been successful. Thioridazine was patented in 1966 by the Swiss pharmaceutical company Sandoz, which is now part of Novartis AG. Thioridazine was given the name Melleril at the time. At present, it is still used as a generic drug. The active ingredient is usually used as a tartrate or water-soluble hydrochloride. However, Melleril has been withdrawn from the market in the United States and Europe by its largest manufacturer, Novartis, because it can cause dangerous cardiac arrhythmias.
Pharmacological action
Neuroleptics are used to treat schizophrenia. Thus, they possess sedative and antipsychotic properties. Mental disorders in schizophrenia are primarily caused by neurotransmitters such as serotonin and dopamine. For this reason, inhibition of the corresponding receptors within the central nervous system is necessary. For this purpose, the serotonin or dopamine receptors are bound with the help of various drugs. In this way, they regulate the influence of the neurotransmitters as antagonists on the patient’s psyche. Thioridazine is one of the dopamine antagonists. The drug’s mode of action is based on blocking dopamine receptors, which in turn has an inhibitory effect on the effects of dopamine. In addition, the neuroleptic suppresses the further release and reproduction of dopamine. However, the sedative effect of thioridazine is much stronger than its antipsychotic properties. Low-potency neuroleptics such as thioridazine are not suitable for the sole therapy of psychosis. At higher doses, other receptors such as histamine receptors, adrenergic receptors and MACh receptors are activated, which in turn leads to increased side effects. A previously unknown effect of thioridazine was revealed by recent research in India. For example, the neuroleptic proved to be successful against highly resistant bacterial strains of the Mycobacterium tuberculosis type, as the active ingredient also has antimicrobial properties. Furthermore, thioridazine can be used as a functional inhibitor of acid sphingomyelinase (FIASMA).
Medical application and use
Thioridazine is administered to treat schizophrenia. In this context, the drug is used to control psychosis, personality disorders, hallucinations, and delusions. Thioridazine is also suitable for the treatment of agitation states. However, the neuroleptic is usually used only as an adjunctive drug or as an alternative in the event of failure of the usual drugs. Thioridazine may also be suitable for the treatment of tuberculosis. However, approval for this purpose has not yet been granted. Provided that the neuroleptic is dosed as prescribed, it is generally considered to be well tolerated. It is usually taken in the form of film-coated tablets. A liquid dosage form is also available for seniors.
Risks and side effects
Taking thioridazine may result in unwanted side effects. The most common side effects include drowsiness, dry mouth, dizziness, blurred vision, fluctuations in blood pressure, and a stuffy nose. In women, milk may sometimes flow from a non-lactating breast.Other conceivable side effects may include twitching, convulsions, tremors, disturbances of motor functions, muscle rigidity, restlessness of movement, pallor of the face, allergic skin reactions, hives, sensitivity to light, a swollen parotid gland, an increase in body temperature, problems with breathing, and painful permanent erections of the penis without sexual motivation. In addition, affected individuals are often unable to maintain a quiet sitting position. In rare cases, depression, nightmares, neuroleptic syndrome, circulatory problems, bowel obstruction, and impaired consciousness or coma also occur. In the worst case, the patient may even die suddenly. If hypersensitivity to thioridazine is present or the patient suffers from pronounced cardiac arrhythmias or severe photosensitivity, the use of the neuroleptic must be discontinued. Combination with drugs that inhibit the cytochrome P4502D6 isoenzyme is also not permitted. These may be beta-blockers, tricyclic antidepressants, or serotonin reuptake inhibitors such as paroxetine or fluoxetine. Exact studies on the use of thioridazine during pregnancy are not available. However, it could be determined that the neuroleptic can penetrate into the placenta. For this reason, a careful weighing of risk and benefit is recommended before use. In the last stage of pregnancy, there is a risk of side effects for the baby. These are manifested by breathing difficulties, shakiness, disturbances in the absorption of food or drowsiness. In addition, thioridazine can enter breast milk, which also carries the risk of side effects in the baby. Therefore, if thioridazine therapy is necessary, weaning should occur beforehand. In children, thioridazine is used only when no other suitable medications are available. The concomitant administration of thioridazine and other drugs may cause interfering interactions. For example, the beta-blocker propranolol, the blood pressure drug pindolol, and antidepressants such as fluvoxamine cause thioridazine to slow metabolism considerably. As a result, there is a risk of conduction disturbance in the heart, which in turn results in serious cardiac arrhythmias.
