Quetiapine is indicated for the treatment of acute and chronic psychotic disorders, including schizophrenia and bipolar disorder. It is used for the treatment of manic episodes associated with bipolar disorder according to DSM-IV criteria, depressive episodes related to bipolar disorder, and maintenance treatment of bipolar I disorder. It is also used in combination with a mood stabilizer to help prevent recurrence of manic, depressive, or mixed episodes.

Quetiapine Fumarate is an atypical psychotropic medicine belonging to the dibenzothiazepine derivative class. It works by blocking multiple neurotransmitter receptors in the brain, including serotonin (5HT1 and 5HT2), dopamine (D1 and D2), histamine (H1), and adrenergic (α1 and α2) receptors. It has little or no affinity for muscarinic cholinergic and benzodiazepine receptors. Its exact mechanism of action is not fully known, but its effectiveness in schizophrenia is believed to result mainly from the combined antagonism of dopamine D2 and serotonin 5HT2 receptors. Blockade of histamine H1 receptors may cause drowsiness, while blockade of adrenergic α1 receptors may lead to orthostatic hypotension.

Acute and chronic psychoses, including schizophrenia: Quetiapine should be administered twice daily, with or without food. The total daily dose for the first four days of therapy is 50 mg (Day 1), 100 mg (Day 2), 200 mg (Day 3) and 300 mg (Day 4). From Day 4 onwards, the dose should be titrated to the usual effective dose range of 300-450 mg/day. However, this may be adjusted, depending on the clinical response and tolerability of the individual patient, within the range 150 to 750 mg/day.

Manic episodes associated with bipolar disorder: Quetiapine should be administered twice daily, with or without food. The total daily dose for the first four days of therapy is 100 mg (Day 1), 200 mg (Day 2), 300 mg (Day 3) and 400 mg (Day 4). Further dosage adjustments up to 800 mg/day by Day 6 should be in increments of no greater than 200 mg/day. The dose may be adjusted depending on clinical response & tolerability of the individual patient, within the range of 200 to 800 mg/day. The usual effective dose is in the range of 400 to 800 mg/day.

Depressive episodes associated with bipolar disorder: Quetiapine should be administered once daily at bedtime, with or without food. The usual dose is 300 mg/day. The daily dose for the first four days of therapy is 50 mg (Day 1), 100 mg (Day 2), 200 mg (Day 3) and 300 mg (Day 4). Quetiapine can be titrated to 400 mg on Day 5 and up to 600 mg by Day 8. Antidepressant efficacy was demonstrated with Quetiapine at 300 mg and 600 mg, however no additional benefit was seen in the 600 mg group during short term treatment.

Maintenance treatment of bipolar I disorder in combination with mood stabilizers: Patients who have responded to Quetiapine in combination therapy with a mood stabiliser for acute treatment of bipolar disorder should continue on Quetiapine therapy at the same dose. Quetiapine dose can be re-adjusted depending on clinical response and tolerability of the individual patient. Efficacy was demonstrated with Quetiapine (administered twice daily totalling 400 mg to 800 mg a day) as combination therapy with a mood stabilizer.

Caution is required when Quetiapine is used together with medicines that may cause electrolyte imbalance or prolong the QT interval. Co-administration with thioridazine or carbamazepine may increase the clearance of Quetiapine. Phenytoin and other microsomal enzyme inducers may also increase Quetiapine metabolism and reduce its effectiveness.

Quetiapine is contraindicated in patients with known hypersensitivity to the drug or any of its components.

Common adverse effects include somnolence, dizziness, dry mouth, withdrawal symptoms after discontinuation, increased serum triglycerides, increased total cholesterol (mainly LDL), reduced HDL cholesterol, weight gain, decreased hemoglobin, and extrapyramidal symptoms.

The safety of Quetiapine during pregnancy has not been fully established. It should only be used if the potential benefit justifies the possible risk to the fetus, and the dose and duration should be kept as low and short as possible. It is not known whether Quetiapine passes into breast milk, so breastfeeding should be avoided during treatment.

Suicide/Suicidal Thoughts or Clinical Worsening: Depression is associated with an increased risk of suicidal thoughts, self-harm, and suicide-related events. This risk may continue until significant improvement or remission occurs. Patients should be closely monitored, especially during the early phase of treatment.

Concomitant Illness: Quetiapine should be used cautiously in patients with cardiovascular disease, cerebrovascular disease, or other conditions that may predispose to hypotension. Orthostatic hypotension may occur, particularly during the initial dose adjustment period.

Seizures: As with other antipsychotic medicines, caution is advised in patients with a history of seizures.

Tardive Dyskinesia and Extrapyramidal Symptoms (EPS): If symptoms of tardive dyskinesia or extrapyramidal symptoms develop, dose reduction or discontinuation of Quetiapine should be considered.

Neuroleptic Malignant Syndrome (NMS): This serious condition may occur during antipsychotic treatment. Quetiapine should be stopped immediately and appropriate medical management should be started.

QT Prolongation: Caution is required when prescribing Quetiapine to patients with cardiovascular disease or a family history of QT interval prolongation.

Neutropenia: Severe neutropenia (<0.5×10⁹/L) has been reported rarely, mostly within the first two months of treatment. Patients should be monitored for signs of infection.

Hyperglycemia and Diabetes Mellitus: Increased blood glucose levels, hyperglycemia, and occasional cases of diabetes mellitus have been reported during treatment with Quetiapine.

Elderly: Use with caution, especially during the initial dosing period. Dose titration should be slower and the therapeutic dose may be lower than in younger adults.
Children and Adolescents: Not recommended for use in patients below 18 years of age.

There is no specific antidote for Quetiapine overdose. Severe overdose may require intensive care, airway management, oxygen support, cardiovascular monitoring, and symptomatic treatment. Hypotension should be treated with IV fluids and sympathomimetic agents, avoiding adrenaline and dopamine. Close monitoring should continue until full recovery.

Atypical neuroleptic drugs

Keep out of the sight and reach of children. Do not use after the expiry date mentioned on the blister pack and carton. Store in a cool, dry place away from light.