**Core Concept**
Chlorpromazine is a typical antipsychotic medication belonging to the phenothiazine class, used primarily for treating schizophrenia and other psychiatric disorders. Its side effects are a result of its action on various neurotransmitter systems in the brain.

**Why the Correct Answer is Right**
Chlorpromazine works by blocking dopamine receptors (D2) in the mesolimbic pathway, which is involved in the regulation of emotions and motivation. This blockade is responsible for its therapeutic effects. However, chlorpromazine also has anticholinergic effects, which can cause dry mouth, constipation, and urinary retention due to its blockade of muscarinic acetylcholine receptors. Additionally, chlorpromazine can cause hypotension due to its alpha-1 adrenergic receptor blockade, leading to vasodilation.

**Why Each Wrong Option is Incorrect**
**Option A:** is not a common side effect of chlorpromazine. While it may cause some degree of weight gain, it is not a prominent side effect compared to others.
**Option B:** is a known side effect of chlorpromazine due to its anticholinergic properties, which can cause dry mouth, constipation, and urinary retention.
**Option C:** is also a known side effect of chlorpromazine, as it can cause hypotension due to its alpha-1 adrenergic receptor blockade.

**Clinical Pearl / High-Yield Fact**
Chlorpromazine can also cause a rare but serious side effect called agranulocytosis, a decrease in white blood cell count, which can increase the risk of infections. This is more common in patients with a history of bone marrow suppression or those taking other medications that suppress the immune system.

**Correct Answer: A. Weight gain is not a common side effect of chlorpromazine.**