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quetiapine

Quetiapine is an atypical antipsychotic drug. From the chemical point of view it is a dibenzothiazepina.

Quetiapine - Chemical Structure

Quetiapine has an efficacy similar to that of haloperidol (another antipsychotic drug) in the treatment of positive symptoms of schizophrenia, but is also able to control negative symptoms and to induce fewer extrapyramidal side effects.

Indications

For what it uses

The use of quetiapine is indicated for the treatment of:

  • Schizophrenia;
  • Mania;
  • Bipolar depression;
  • Major depressive disorder, usually in association with antidepressant drugs.

Quetiapine can also be used for the prevention of recurrences in bipolar disorder.

Warnings

Depression is associated with an increased risk of suicidal thoughts and behavior and suicide attempt. Before quetiapine exerts its therapeutic action, it may take a certain period of time (usually two weeks, but sometimes even longer), so patients must be carefully monitored until a significant improvement in the disease occurs. Furthermore, suicidal ideation and behavior could intensify in the event of abrupt withdrawal of therapy, therefore a gradual interruption of treatment is advisable.

Since quetiapine may cause an increase in body weight, patients being treated with the drug should be carefully monitored.

Quetiapine can cause decreased white blood cell levels in the bloodstream, so patients must be kept under control.

Quetiapine can cause neuroleptic malignant syndrome, in the event of the onset of this syndrome, immediate interruption of therapy and pharmacological treatment may be necessary.

It is necessary to inform the doctor if the patients fall into one of the following categories:

  • Patients who have suffered - or with a family history - of heart disease;
  • Patients suffering from hypotension;
  • Patients who have had a stroke, especially if they are elderly patients;
  • Patients with liver disease;
  • Patients with epilepsy or seizure disorders;
  • Diabetic patients or those at risk of developing diabetes;
  • Patients who suffered from decreased white blood cell levels in the bloodstream.

Since quetiapine can promote the formation of blood clots, the drug should be used with caution in patients with a history - including family history - of coagulation disorders.

The use of quetiapine in elderly patients with dementia increases the risk of stroke and death.

Since quetiapine can induce sleepiness, driving and using machines is not recommended.

Interactions

The use of quetiapine should be avoided when taking:

  • Antiviral drugs used for HIV treatment;
  • Azole antifungal drugs ;
  • Erythromycin and clarithromycin, antibiotic drugs;
  • Nefazodone, an antidepressant drug.

Before taking quetiapine, you must tell your doctor if you are taking any of the following drugs:

  • Drugs for the treatment of epilepsy, such as - for example - phenytoin and carbamazepine;
  • Drugs to treat hypertension;
  • Barbiturates;
  • Thioridazine, an antipsychotic drug;
  • Drugs that can cause electrolyte imbalance and that - as a result - can affect the heart;
  • Drugs that can cause constipation.

In any case, you must inform your doctor if you are taking - or if you have recently been taken - drugs of any kind, including over-the-counter drugs and herbal and cosmetic products.

Since the concomitant intake of alcohol and quetiapine may favor the onset of drowsiness, this association is not recommended.

Grapefruit and its derivatives contain substances that may be able to influence the action of quetiapine.

Quetiapine should not be taken in the presence of food .

Side effects

Quetiapine can cause many side effects, although not all patients experience them. The type of side effects and the intensity with which they occur depend on the sensitivity that each individual has towards the drug.

Below are the main side effects that may occur following treatment with the drug.

Nervous system disorders

Treatment with quetiapine may cause:

  • Dizziness which can also cause falls;
  • Headache;
  • Drowsiness;
  • Tremor;
  • Muscle restlessness or stiffness;
  • Weakness;
  • Fainting;
  • Communication and language disorders;
  • Convulsions or seizures;
  • Extrapyramidal symptoms.

Psychiatric disorders

Treatment with quetiapine can cause abnormal dreams, nightmares, irritability, suicidal thoughts, sleepwalking and can lead to a worsening of depressive illness.

Malignant Neuroleptic Syndrome

Neuroleptic Malignant Syndrome is a neurological disorder characterized by:

  • Temperature;
  • Dehydration;
  • Muscle stiffness;
  • akinesia;
  • Sweating;
  • Tachycardia;
  • Arrhythmia;
  • Changes in the state of consciousness that can progress to stupor and coma.

If these symptoms appear, quetiapine treatment should be stopped immediately and a doctor should be contacted.

Gastrointestinal disorders

Treatment with quetiapine may cause indigestion, constipation, vomiting, intestinal obstruction and pancreatitis.

Suspension symptoms

Abrupt discontinuation of quetiapine treatment can cause so-called withdrawal symptoms. These symptoms are insomnia, nausea, vomiting, headache, diarrhea, dizziness and irritability.

Cardiovascular disorders

Quetiapine therapy can cause an acceleration of the heart rate, hypotension, orthostatic hypotension (ie a sudden drop in blood pressure when passing from an extended position or sitting to an upright position) and prolongation of the QT interval (the interval of time required to the ventricular myocardium to depolarize and repolarize). In addition, the drug can promote thrombus formation.

Hepatobiliary disorders

Treatment with quetiapine can cause hepatitis and jaundice.

Reproductive system and breast disorders

Quetiapine therapy can cause sexual dysfunction, breast swelling and galactorrhoea (abnormal milk secretion) in both sexes.

In women, quetiapine can cause menstrual disorders.

In men, however, the drug can cause priapism (ie a long and painful erection not accompanied by sexual excitement).

Allergic reactions

Quetiapine can trigger allergic reactions in sensitive individuals that may manifest themselves in the form of bruising, swelling of the skin and area around the mouth, difficulty breathing or anaphylactic shock.

Skin and subcutaneous tissue disorders

Treatment with quetiapine may cause angioedema, rash and may promote the onset of Stevens-Johnson syndrome (a more severe variant of polymorphic erythema).

Other side effects

Other side effects that may arise from taking quetiapine are:

  • Decreased blood levels of white blood cells, with consequent increased susceptibility to contraction of infections;
  • Dry mouth;
  • Increased body weight;
  • Stuffy nose;
  • Swelling of arms and legs;
  • Increased blood glucose levels;
  • Blurred vision;
  • Temperature;
  • Hypothermia;
  • Dyspnoea;
  • Difficulty swallowing;
  • Restless legs syndrome;
  • Worsening of pre-existing diabetes;
  • Urination difficulties;
  • Rhabdomyolysis (rupture of skeletal muscle cells and release into the bloodstream of substances present in the musculature);
  • Inappropriate secretion of the antidiuretic hormone.

Overdose

Symptoms that may occur following an overdose of quetiapine are drowsiness, dizziness and heart rate changes. If you suspect you have overdosed, you should tell your doctor immediately.

Action mechanism

Quetiapine is able to perform its antipsychotic action by antagonizing the 5-HT 2A receptors of serotonin (5-HT) and - albeit to a lesser extent - antagonizing the D 2 dopamine receptors (DA). Furthermore, quetiapine has affinity for α 1 and α 2 adrenergic receptors and for histamine H 1 receptors.

Mode of Use - Posology

Quetiapine is available for oral administration as tablets. The tablets should be swallowed whole with the help of a little water and should be taken away from meals.

The dose of quetiapine - initial and maintenance - must be established by the doctor on an individual basis, depending on the type and severity of the pathology to be treated.

Generally, the daily maintenance dose is 150-800 mg of drug.

In elderly patients and in patients with liver disease, a decrease in the dose of quetiapine administered may be necessary.

Pregnancy and breastfeeding

Pregnant women should consult their doctor before taking quetiapine.

Infants - whose mothers took quetiapine in the last trimester of pregnancy - experienced withdrawal symptoms such as tremor, muscle stiffness, muscle weakness, drowsiness, agitation, feeding difficulties and respiratory problems.

Breast-feeding mothers should not take quetiapine.

Contraindications

The use of quetiapine is contraindicated in the following cases:

  • Known hypersensitivity to quetiapine;
  • In case of taking some types of drugs (see the paragraph "Interactions with other drugs");
  • In children and adolescents under 18 years of age;
  • During breastfeeding.

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