Antipsychotic medications are used to treat psychotic disorders such as schizophrenia, bipolar disorder, and delusional disorder. They work by blocking dopamine receptors in the brain, which reduces the positive symptoms of psychosis such as hallucinations, delusions, and agitation. However, antipsychotic medications also have many adverse effects, some of which are related to their dopamine-blocking action and some of which are related to their effects on other neurotransmitters such as serotonin, acetylcholine, histamine, and norepinephrine.

Some of the common adverse effects of antipsychotic medications are:

• Sedation: This is caused by the blockade of histamine receptors in the brain and can affect alertness, concentration, and coordination.

Sedation is more common with older antipsychotics such as chlorpromazine and haloperidol than with newer ones such as risperidone and quetiapine.

• Dry mouth: This is caused by the blockade of acetylcholine receptors in the salivary glands and can lead to dental problems, difficulty swallowing, and increased thirst.

Dry mouth is more common with older antipsychotics than with newer ones.

• Blurred vision: This is also caused by the blockade of acetylcholine receptors in the eye muscles and can affect visual acuity and accommodation.

Blurred vision is more common with older antipsychotics than with newer ones.

• Weight gain: This is caused by the blockade of serotonin receptors in the hypothalamus and can lead to increased appetite, metabolic changes, and obesity.

Weight gain is more common with newer antipsychotics such as olanzapine and clozapine than with older ones.

Therefore, weight loss is not a common adverse effect of antipsychotic medications and is the correct answer.