What Side Effects Can Antipsychotics Cause?

Antipsychotics can cause a wide range of side effects. You might get some, none, or they may settle after a few weeks as your body adjusts.

Before starting, stopping, or changing your medication, always talk to your doctor.

Common Side Effects Across All Antipsychotics

Most antipsychotics can cause some everyday side effects, especially early on, such as:

• Drowsiness or feeling very tired
• Dizziness or lightheadedness
• Dry mouth
• Weight gain
• Constipation
• Blurred vision
• Feeling restless or unable to sit still
• Changes in mood or anxiety levels

Side Effects by Antipsychotic Type

First-Generation (Typical)

• Movement problems (tremors, stiffness, or muscle spasms)
• Parkinsonism-like symptoms
• Restlessness (akathisia)
• Tardive dyskinesia (uncontrollable movements, especially of the face)
• Drowsiness

Second-Generation (Atypical)

• Metabolic changes (weight gain, raised blood sugar, high cholesterol)
• Hormonal changes (high prolactin levels)
• Drowsiness or sedation
• Dizziness
• Some risk of movement problems (less than older antipsychotics)

Rare but Serious Side Effects

• Neuroleptic Malignant Syndrome (NMS): A rare, life-threatening reaction with high fever, severe stiffness, confusion and rapid heartbeat.
• Agranulocytosis: A serious drop in white blood cells (mainly with clozapine).
• Seizures: More likely with certain antipsychotics or high doses.
• Severe allergic reactions: Swelling of face or throat, difficulty breathing.

How Long Do Side Effects Last?

Some common side effects like tiredness or dizziness may fade in a few weeks as your body adjusts. Others, like weight gain or movement problems, may last longer — speak to your doctor if they don’t improve.

When to Seek Help

Contact your GP or pharmacist if:

• Side effects are bothersome or don’t go away
• You notice new symptoms like significant weight gain or blood sugar changes
• You’re unsure if what you’re feeling is normal for your medication

Call emergency services if:

• You show signs of Neuroleptic Malignant Syndrome (NMS): sudden high fever, severe stiffness, confusion
• You have a seizure or lose consciousness
• You have a severe allergic reaction: swelling of face or throat, trouble breathing