Indications

QTP is indicated for the treatment of Acute and chronic psychoses, including schizophrenia, Bipolar Disorder including: treatment of manic episodes satisfying DSM-IV criteria for mania associated with bipolar  disorder, treatment of depressive episodes associated with bipolar disorder, maintenance treatment of bipolar I disorder, in combination with a mood stabilizer, for the prevention of recurrence of manic, depressive or mixed episodes.

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Pharmacology

Quetiapine Fumarate is an atypical psychotropic agent belonging to a chemical class, the dibenzothiazepine derivatives. Quetiapine is an antagonist at multiple neurotransmitter receptors in the brain: serotonin 5HT_1A and 5HT₂, dopamine D₁ and D₂, histamine H₁, and adrenergic α1 and α2 receptors. Quetiapine has no appreciable affinity at cholinergic muscarinic and benzodiazepine receptors. The mechanism of action of Quetiapine is unknown. However, it has been proposed that this drug's efficacy in schizophrenia is mediated through a combination of dopamine D₂ and serotonin 5HT₂ antagonism. Quetiapine's antagonism of histamine H₁ receptors may explain the somnolence and that of adrenergic a receptors may explain the orthostatic hypotension observed with this drug.

Dosage & Administration

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 800mg/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 800mg/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 600mg by Day 8. Antidepressant efficacy was demonstrated with Quetiapine at 300mg and 600 mg, however no additional benefit was seen in the 600mg 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 400mg to 800mg a day) as combination therapy with a mood stabilizer.

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Interaction

Caution should be exercised when QTP is used concomitantly with medicines known to cause electrolyte imbalance or to increase QT interval. Co-administration of QTP and thioridazine or carbamazepine caused increases in the clearance of QTP. Co-administration of QTP with another microsomal enzyme inducer, phenytoin, also caused increases in the clearance of QTP.

Contraindications

Quetiapine is contra-indicated in patients who are hypersensitive to it.

Side Effects

The most commonly reported Adverse Drug Reactions (ADRs) with QTP are somnolence, dizziness, dry mouth, withdrawal (discontinuation) symptoms, elevations in serum triglyceride levels, elevations in total cholesterol (predominantly LDL cholesterol), decreases in HDL cholesterol, weight gain, decreased haemoglobin and extrapyramidal symptoms.

Pregnancy & Lactation

The safety and efficacy of Quetiapine during human pregnancy have not been established. Therefore, Quetiapine should only be used during pregnancy if the benefits justify the potential risks and the administered dose and duration of treatment should be as low and as short as possible. The degree to which Quetiapine is excreted into human milk is unknown. Women who are breast-feeding should therefore be advised to avoid breast-feeding while taking Quetiapine.

Precautions & Warnings

• Suicide/suicidal thoughts or clinical worsening: Depression is associated with an increased risk of suicidal thoughts, self-harm and suicide (suicide-related events). This risk persists until significant remission occurs. 
• Concomitant Illness: QTP should be used with caution in patients with known cardiovascular disease, cerebrovascular disease, or other conditions predisposing to hypotension. QTP may induce orthostatic hypotension especially during the initial dose-titration period. 
• Seizures: As with other antipsychotics, caution is recommended when treating patients with a history of seizures.
• Tardive Dyskinesia and Extrapyramidal Symptoms (EPS): If signs and symptoms of tardive dyskinesia appear, dose reduction or discontinuation of QTP should be considered.
• Neuroleptic Malignant Syndrome: This syndrome has been associated with antipsychotic treatment. QTP should be discontinued and appropriate medical treatment given.
• QT Prolongation: As with other antipsychotics, caution should be exercised when QTP is prescribed in patients with cardiovascular disease or family history of QT prolongation.
• Neutropenia: Severe neutropenia (<0.5x109/L) has been uncommonly reported in QTP clinical trials. Most cases of severe neutropenia have occurred within the first two months of starting therapy with QTP.
• Hyperglycemia & diabetes mellitus: Increases in blood glucose and hyperglycaemia, and occasional reports of diabetes, have been observed in clinical trials with QTP.

Use in Special Populations

Elderly: As with other antipsychotics, QTP should be used with caution in the elderly, especially during the initial dosing period. The rate of dose titration may need to be slower, and the daily therapeutic dose lower, than that used in younger patients, depending on the clinical response and tolerability of the individual patient. The mean plasma clearance of QTP was reduced by 30% to 50% in elderly subjects when compared with younger patients.

Children and Adolescents: QTP is not indicated for use in children and adolescents below 18 years of age.

Overdose Effects

In clinical trials, survival has been reported in acute overdoses of up to 30 grams of QTP. There is no specific antidote to QTP. In cases of severe intoxication, the possibility of multiple drug involvement should be considered, and intensive care procedures are recommended, including establishing and maintaining a patent airway, ensuring adequate oxygenation and ventilation, and monitoring and support of the cardiovascular system. In cases of QTP overdose, refractory hypotension should be treated with appropriate measures such as intravenous fluids and/or sympathomimetic agents (adrenaline and dopamine should be avoided, since beta stimulation may worsen hypotension in the setting of QTP-induced alpha blockade). Close medical supervision and monitoring should be continued until the patient recovers.

Therapeutic Class

Atypical neuroleptic drugs

Storage Conditions

Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date which is stated on the blister pack and the carton. The expiry date refers to the last day of that month. Store in a cool and dry place away from light.