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Quetiapine is an antipsychotic drug. It can be used to treat several illnesses such as schizophrenia, bipolar disorder, and along with an antidepressant to treat major depressive disorder.
 BRAND NAMES
 MECHANISM OF ACTION
Quetiapine, is an antipsychotic drug belonging to the class of atypical antipsychotics (Second generation antipsychotics). Other atypical antipsychotic drugs include Risperidone, Paliperidone, Olanzapine, Aripiprazole, Clozapine, Ziprasidone and Amisulpride.
Atypical antipsychotics have become an increasingly popular alternative to typical antipsychotics (First generation antipsychotics) like haloperidol because they are less likely to cause extra-pyrammidal side-effects (EPS), drug induced involuntary movements, than are the older drugs.
Quetiapine and its active metabolite, Norquetiapine interact with a broad range of neurotransmitter receptors. Its efficacy in Schizophrenia is mediated through a combination of antagonism at dopamine D2 receptors in the mesolimbic pathway and serotonin 5HT2A receptors in the frontal cortex. Antagonism at D2 receptors relieves positive symptoms while antagonism at 5HT2A receptors relieves negative symptoms of schizophrenia.
The greater selectivity at 5HT2a receptors than for D2 receptors explains the low frequency of extrapyramidal side effects.
Norquetiapin is also a potent inhibitor of the norepinephrine transporter (NET) that may contribute to its efficacy in bipolar depression and major depressive disorder.
Antagonism of histamine H1 receptors may explain the somnolence, antagonism of adrenergic α1b receptors may explain the orthostatic hypotension, and antagonism at muscarinic M1 receptors may explain the anticholinergic effects (negligible) observed with this drug.
- Schizophrenia: People with schizophrenia may hear or feel things that are not there, believe things that are not true or feel unusually suspicious, anxious, confused, guilty, tense or depressed.
- Bipolar disorder:
- Acute and maintenanace treatment of manic or mixed episodes associated with bipolar I disorder, as either monotherapy or adjunct therapy to lithium carbonate or divalproex. Bipolar disorder, a mental illness in which patients have manic episodes (periods of abnormally high mood), alternating with periods of normal mood, as well as episodes of depression. During mania, patients experience episodes of overactivity, elation or irritability. During depression, patients may feel depressed or guilty, lack energy, lose their appetite and have trouble sleeping.
- Acute treatment of depressive episodes associated with bipolar disorder
- Major depressive disorder: The Extended release tablets are approved by FDA as an adjunctive therapy to antidepressants in major depressive disorder
- Quetiapine is also used for sleep disorders
- Schizophrenia in adults: Starting dose: 25 mg twice daily; Target dose: 150-750 mg/day within several days (increase 25-50 mg every 1-2 days).
- Bipolar I disorder (Manic or mixed) in adults: The starting dose is 50 mg twice daily; Target dose: 400-800 mg/day within several days (increase 25-50 mg every 1-2 days).
- Bipolar Disorder(Depressive episodes in adults): The starting dose is 50 mg once daily; Target dose: 300 mg/day within several days (increase 25-50 mg every 1-2 days).
Tablets can be taken with or without food
Extended release tablets:
- Schizophrenia in adults: Starting dose: 300 mg daily; Target dose: 400-800 mg/day within several days.
- Bipolar I disorder (Manic or mixed) in adults: The starting dose is 300 mg daily; Target dose: 400-800 mg/day within several days.
- Bipolar Disorder (Depressive episodes in adults): The starting dose is 50 mg once daily; Target dose: 300 mg/day within several days.
- Major depressive disorder: The starting dose is 50 mg once daily; Target dose: 150-300 mg/day within several days.
It is recommended that Extended release tablets be taken without food or with a light meal, once daily, preferably in the evening.
- Known hypersensitivity to Quetiapine
 WARNINGS AND PRECAUTIONS
Quetiapine is extensively metabolized by CYP3A4:
- Potent CYP3A4 inhibitors (e.g. Ritonavir, atazanavir, clarithromycin, indinavir, itraconazole, nefazodone, nelfinavir, saquinavir, ketoconazole, telithromycin increase Quetiapine plasma levels. Reduce Quetiapine to one sixth.
- CYP3A4 inducers (e.g. phenytoin, carbamazepine, rifampin and phenobarbital) increased the mean oral clearance of Quetiapine by 5-fold. Increase Quetiapine dose up to 5 fold.
 PREGNANCY AND LACTATION
- Pregnancy Category C (US). Quetiapine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.
- Nursing Mothers: Quetiapine is excreted in breast milk. It is recommended that women receiving Quetiapine should not breast-feed.
 SIDE EFFECTS
Common adverse reactions: Orthostatic hypotension (temporary), drowsiness, dizziness, constipation, pharyngitis, weight gain (less weight gain than clozapine or olanzapine), dyspepsia, nasal congestion, mild asthenia and dry mouth
Extrapyramidal symptoms (EPS): very low incidence