Thioridazine is a drug that acts as an antipsychotic (first generation) and as an anxiolytic, decreasing anxious and psychotic symptoms. It is mainly used for schizophrenia in case other antipsychotic drugs have not proved beneficial to the patient.

However, its indications go beyond that, and it is also used for conduct disorders, psychotic depression and anxiety, among others. We will also know its general characteristics, its mechanism of action, its pharmacokinetics and its adverse reactions.

Thioridazine: general characteristics

Thioridazine is an anxiolytic and antipsychotic drug; specifically, is a phenothiazine (a group of antipsychotic drugs). Chemically it is similar to mesoridazine (one of its metabolites).

Thioridazine is indicated for the treatment of some psychotic disorders such as schizophrenia, for anxiety associated with depression, conduct disorders in children and dementia. What it does is decrease the abnormal excitement in the brain.

In addition, it is the phenothiazine with the least extrapyramidal effects, i.e., movement-related disorders, emerging as a type of side effect. However, its sedative and anxiolytic effects are important .

Contraindications to thioridazine are: hypersensitivity to thioridazine itself or to other phenothiazines, severe CNS (Central Nervous System) depression, comatose states, as well as severe hypotension or cardiac hypertension.

Mechanism of action of this drug

The mechanism of action of thioridazine is the blocking of the post-synaptic D2 dopamine receptors in the mesolimbic system of the brain . The blockade also explains the extrapyramidal effects seen with the taking of thioridazine.

On the other hand, thioridazine also blocks cholinergic (acetylcholine) and alpha-adrenergic (adrenaline) receptors, leading to side effects such as sedation, muscle relaxation and cardiovascular effects (e.g. hypotension, altered electrocardiographic profile and reflex tachycardia).

Indications: disorders in which it is used

Thioridazine is an antipsychotic that is indicated for the treatment of psychotic disorders, such as schizophrenia or psychotic depression. In some cases it is also used for severe behavioural disorders in children (e.g. aggression and hyperexcitability), difficulties in maintaining attention, dementia and anxiety associated with depressive disorder.

Specifically, thioridazine is used to control the manifestations or symptoms of psychotic disorders . In the case of schizophrenia, thioridazine is used as an alternative treatment in case 2 other drugs have previously failed to produce good results or there are sometimes serious side effects for the patient. It is also indicated for sleep disorders and fears in the elderly.

As for depression, is indicated for moderate or severe short-term depression , with accompanying symptoms such as anxiety.

Thioridazine should be used very cautiously in patients with Parkinson’s disease or liver disease.

Side effects

The adverse reactions that thioridazine can cause, like other phenothiazines, are major cardiovascular reactions . It is for this reason that thioridazine is prescribed to patients who have not responded with other types of antipsychotic drugs.

Also can produce sedation, dry mouth, vertigo, orthostatic hypotension, skin rashes, vision disorders , ejaculation disorders, photosensitivity, urinary incontinence and galactorrhea (occasional).

The use of thioridazine is not recommended during pregnancy and breastfeeding. When driving, great caution should be exercised, as the drug can cause significant effects such as drowsiness and decreased responsiveness.

It may also cause visual disturbances (blurred vision, decreased night vision, and scotoma), although these may disappear if the thioridazine is removed early. However, vision does not always improve, despite stopping the drug, as has been seen in some cases.

Some facts

Studies with thioridazine showed that 60% of patients taking the drug suffered from sexual dysfunction (compared to 25% of patients treated with other antipsychotics).

Another side effect that can occur, tardive dyskinesia, occurs in 4% of cases treated with thioridazine, annually (during the first 5-6 years of treatment).

Pharmacokinetics

Thioridazine is given orally and is rapidly absorbed. The therapeutic effects are usually maximal 6 weeks after starting treatment with thioridazine . Phenothiazines such as thioridazine cross the blood-brain barrier and are distributed throughout all body tissues.

It also crosses the placenta and is excreted into the mother’s milk, so there must be a lot of caution regarding its use.

How do you take it?

Thioridazine is usually taken in tablet form by mouth , usually 2 to 4 times a day (50 to 800 mg/day/voice). It is recommended that it be taken at the same time every day. For any questions that have not been answered by the doctor or pharmacist, please consult the prescription instructions.

The doctor usually prescribes thioridazine at a low dose and gradually (and according to the patient’s needs) increases it until the symptoms are under control. Then, with symptoms under control, the doctor will probably reduce the dose.

Although thioridazine may help to control or alleviate certain symptoms, it does not “cure” any pathology; that is, it is always advisable to follow a psychological treatment combined with the pharmacological one . In addition, having a support network of family (and friends) will always be important for the treatment and improvement of the patient.

Bibliographic references:

  • MedlinePlus. (2017). Thioridazine.
  • Stahl, S.M. (2002). Essential Psychopharmacology. Neuroscientific bases and clinical applications. Barcelona: Ariel.
  • Vademecum. (2015). Thioridazine.