From the Guidelines
Quetiapine 25 mg can cause several adverse effects, including drowsiness, dizziness, dry mouth, constipation, increased appetite, and weight gain, as well as more serious but less common effects like abnormal movements and metabolic changes, as noted in guidelines for managing behavior and mood disorders 1.
Common Adverse Effects
- Drowsiness
- Dizziness
- Dry mouth
- Constipation
- Increased appetite
- Weight gain These effects are typically less severe at lower doses like 25 mg, as compared to higher doses used for conditions such as schizophrenia or bipolar disorder.
Less Common but Serious Adverse Effects
- Abnormal movements (extrapyramidal symptoms), though these are rare at 25 mg
- Metabolic changes including elevated blood sugar, cholesterol, and triglycerides, even at lower doses Elderly patients may experience increased confusion or sedation and should be monitored closely, as the sedative effects of quetiapine are most pronounced when starting the medication, and it's often taken at bedtime to minimize disruption 1. Patients should avoid driving or operating machinery until they know how the medication affects them.
Mechanism of Action
These side effects occur because quetiapine blocks multiple neurotransmitter receptors including dopamine, serotonin, and histamine receptors in the brain, with the histamine blockade primarily responsible for the sedation effects, as discussed in the context of treating behavior and mood disorders 1.
From the FDA Drug Label
Table 10 enumerates the incidence, rounded to the nearest percent, of adverse reactions that occurred during therapy (up to 3 weeks) of acute mania in 2% or more of patients treated with quetiapine (doses ranging from 100 to 800 mg/day) Table 11 enumerates the incidence, rounded to the nearest percent, of adverse reactions that occurred during therapy (up to 8 weeks) of bipolar depression in 2% or more of patients treated with quetiapine (doses of 300 and 600 mg/day) The most common adverse effects of quetiapine are:
- Somnolence (57%)
- Dry mouth (44%)
- Dizziness (18%)
- Constipation (10%)
- Lethargy (5%) Other adverse effects include:
- Dyspepsia
- Fatigue
- Vomiting
- Increased appetite
- Lethargy
- Nasal congestion
- Orthostatic hypotension
- Akathisia
- Palpitations
- Vision blurred
- Weight increased
- Arthralgia
- Paraesthesia
- Cough
- Extrapyramidal disorder
- Irritability
- Dysarthria
- Hypersomnia
- Sinus congestion
- Abnormal dreams
- Tremor
- Gastroesophageal reflux disease
- Pain in extremity
- Asthenia
- Balance disorder
- Hypoaesthesia
- Dysphagia
- Restless legs syndrome 2 2
From the Research
Adverse Effects of Quetiapine 25 mg
- The most commonly reported adverse events associated with quetiapine use are:
- Somnolence (25-39%)
- Dizziness (15-27%)
- Headache (10-23%)
- Postural hypotension (6-18%)
- Weight gain (11-30%) 3
- Compared to risperidone and olanzapine, quetiapine had a significantly lower risk of mortality, reduced rate of cerebrovascular events, and less metabolic disorders compared to olanzapine, but higher metabolic disorders compared to risperidone 3
- Quetiapine, risperidone, and olanzapine, given as adjunctive treatment with SSRIs or SNRIs, can significantly and equally improve depressive and psychotic symptoms in the short-term treatment of major depression with psychotic features 4
- The risk of acute major cardiovascular events was similar with the use of olanzapine, quetiapine, and risperidone in young and middle-aged outpatients 5
- After propensity score matching, there were no statistical differences in cardiovascular disease incidence between olanzapine and either risperidone or quetiapine 6
Specific Adverse Effects
- Cognitive impairment: quetiapine resulted in significantly greater cognitive impairment compared to placebo in patients with parkinsonism, but not in patients with dementia 3
- Falls and injury: quetiapine had an increased rate of falls and injury compared to risperidone and olanzapine 3
- Metabolic disorders: quetiapine had less metabolic disorders compared to olanzapine, but higher metabolic disorders compared to risperidone 3
- Weight gain: quetiapine was associated with a slight increase in weight, which was statistically significant in one study 4