Quetiapine is a commonly used atypical antipsychotic medication. Indications include schizophrenia, bipolar disorder, depression, and acute delirium.

Mechanism

• Dopamine, serotonin and adrenergic antagonist
• Antihistamine
• Binds very strongly to serotonin (5-HT) receptors

Uses

Used in schizophrenia and bipolar disorder most widely. Also quite commonly used in acute delirium in critically ill patients (e.g. in ICU).
Cochrane reviews^1,2 suggest that it is about equally as potent as typical antipsychotics, with fewer side effects, particularly the extrapyramidal / movement related side effects, and that it is similar to other atypical antipsychotics in its profile, although probably slightly less effective than olanzapine and risperidone, albeit with fewer extrapyramidal side effects, and is less likely to cause hyperprolacimaemia.

Adverse Effects

• Dry Mouth
• Dizziness
• Headache
• Drowsiness / sedation – in long term usage this effect reduces
• Hypertension
• Orthostatic hypotension
• Weight gain
• Prolonged QT – avoid using with other medications that can cause the same
• Dystonias
• Akathisia – a feeling of motor restlessness which can present several days or weeks after treatment is commenced
• Tardive Dyskinesia
• Neuroleptic Malignant Syndrome (NMS)

Cautions

• Be wary in parkinsons and lewy body dementia as can exacerbate symptoms
• Epilepsy – may alter seizure threshold
• Respiratory failure – can cause respiratory depression
• Elderly – use of antipsychotics is associated with higher risk of stroke and death. Risk is greater with high doses and typical antipsychotics. Start with lower doses and increase slowly.

Overdose

Can cause:

• Tachycardia
• Hypotension
• Excessive sedation

Rarely may cause:

• Arrhythmias (QT prolongation in particular)
• Can cause death

Typical doses

Schizophrenia / bipolar disorder

• Once daily or BD doses
• Available in both standard and prolonged release, both can be used once daily, standard release is sometimes used BD
• Usual starting dose of 25-50mg OD, titrated up to a maximum of 300-600mg daily as required

Acute delirium

• Start with small doses as required – e.g. 12.5mg nocte
• Be wary in the elderly

References

• Quetiapine versus typical antipsychotic medications for schizophrenia
• Quetiapine versus other atypical antipsychotics for schizophrenia

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