Seroquel XR Side Effects: What to Expect and When to Call Your Doctor

Seroquel XR (quetiapine fumarate extended-release) is an effective medication for schizophrenia, bipolar disorder, and depression — but like all antipsychotics, it has a distinct side effect profile that patients and caregivers should understand before and during treatment. This guide explains the most common side effects, the serious warnings you must know, and the specific signals that require you to call your doctor or seek emergency care.

Boxed Warnings: The Most Serious Risks

Seroquel XR carries two FDA-required boxed warnings — the highest level of safety alert on a medication:

• Increased mortality in elderly patients with dementia-related psychosis: Antipsychotic drugs, including quetiapine, are associated with an increased risk of death in elderly patients being treated for dementia-related behavioral symptoms. Seroquel XR is not approved for this use. If an elderly family member is prescribed quetiapine for dementia-related behavior, ask their doctor about the specific risks and alternatives.
• Suicidal thoughts and behaviors: Antidepressants (and medications used with antidepressants) have been associated with increased suicidal thoughts in children, adolescents, and young adults, particularly in the first months of treatment or when doses are changed. All patients starting quetiapine XR should be closely monitored for worsening depression, unusual mood changes, agitation, or suicidal thinking.

Common Side Effects of Seroquel XR

These side effects are experienced by a meaningful percentage of patients, especially at the start of treatment. Many improve over the first few weeks:

• Drowsiness/sedation: The most common side effect. The extended-release formulation reduces peak sedation compared to IR, but drowsiness is still common, especially at the start of treatment and at higher doses. Taking Seroquel XR in the evening minimizes daytime impairment.
• Weight gain: Quetiapine XR can cause weight gain, particularly with long-term use. Monitor weight regularly and discuss diet and exercise strategies with your doctor.
• Dry mouth: Very common, especially during the first few weeks. Drinking water regularly, chewing sugar-free gum, or using saliva substitutes can help.
• Dizziness / orthostatic hypotension: Quetiapine blocks alpha-adrenergic receptors, causing blood pressure to drop when standing up. Rise slowly from sitting or lying positions, especially in the first weeks of treatment.
• Constipation: Common due to anticholinergic effects. Increased fluid intake and dietary fiber can help.
• Increased appetite and food cravings: Contributes to weight gain. Discuss strategies for healthy eating with your healthcare provider.
• Headache, nausea, and fatigue: Often improve after the first few weeks as your body adjusts to the medication.
• Elevated heart rate (tachycardia): A mild increase in resting heart rate is common, particularly at the start of therapy.

Serious Side Effects: Call Your Doctor Right Away

The following side effects are less common but require prompt medical evaluation:

• Metabolic changes: High blood sugar (hyperglycemia), new or worsening diabetes, and dyslipidemia (elevated LDL, lowered HDL, elevated triglycerides) have all been reported. Your doctor should monitor fasting glucose and lipids periodically.
• Tardive dyskinesia (TD): A movement disorder causing repetitive, involuntary movements of the face, tongue, lips, or limbs. Risk increases with duration of use and higher doses. May be permanent. Report any unusual movements to your doctor immediately.
• QTc prolongation: Quetiapine can prolong the QT interval on ECG. This may increase the risk of serious cardiac arrhythmias, particularly in combination with other QTc-prolonging drugs. Tell your doctor about all medications you take.
• Low white blood cell count (leukopenia/neutropenia): Rarely, quetiapine can reduce white blood cell counts, increasing infection risk. Report fever, chills, or signs of infection promptly.

Emergency: Signs of Neuroleptic Malignant Syndrome (NMS)

Neuroleptic malignant syndrome is a rare but potentially fatal reaction to antipsychotics. Stop Seroquel XR and seek emergency medical care immediately if you experience:

• High fever
• Severe muscle stiffness or rigidity
• Confusion or altered mental status
• Irregular heartbeat or blood pressure changes
• Excessive sweating

Important Monitoring Your Doctor Should Perform

While taking Seroquel XR, your doctor should monitor:

• Weight and body mass index at each visit
• Fasting blood glucose and hemoglobin A1c (diabetes monitoring)
• Lipid panel (cholesterol and triglycerides)
• Blood pressure (orthostatic measurements especially at start of therapy)
• Complete blood count (if clinically indicated)

Read also: Seroquel XR Drug Interactions: What to Avoid and What to Tell Your Doctor