When a high-affinity cholinergic antagonist is replaced by an antipsychotic with no affinity for blocking cholinergic receptors.

When a high-affinity cholinergic antagonist is replaced by an antipsychotic with no affinity for blocking cholinergic receptors.

• A. Cholinergic rebound
• B. Flu-like symptoms
• C. Acute withdrawal effects
• D. Dopaminergic rebound

Answer: (A)

When a strong anticholinergic block is suddenly removed by switching to an antipsychotic with no cholinergic receptor affinity, the previously suppressed acetylcholine activity surges. This abrupt unopposed muscarinic stimulation is called cholinergic rebound. It occurs because the receptors are no longer being blocked, so acetylcholine can exert its effects again at full strength. Clinically you’d expect signs of cholinergic excess such as increased sweating, salivation, lacrimation, bronchorrhea, diarrhea, abdominal cramps, urinary urgency, miosis, and sometimes slowed heart rate. The other ideas don’t fit this mechanism: dopaminergic rebound would involve dopamine receptor activity, and flu-like or generic withdrawal symptoms don’t specifically describe the sudden restoration of cholinergic signaling after removing a strong cholinergic blocker.

When a strong anticholinergic block is suddenly removed by switching to an antipsychotic with no cholinergic receptor affinity, the previously suppressed acetylcholine activity surges. This abrupt unopposed muscarinic stimulation is called cholinergic rebound. It occurs because the receptors are no longer being blocked, so acetylcholine can exert its effects again at full strength. Clinically you’d expect signs of cholinergic excess such as increased sweating, salivation, lacrimation, bronchorrhea, diarrhea, abdominal cramps, urinary urgency, miosis, and sometimes slowed heart rate. The other ideas don’t fit this mechanism: dopaminergic rebound would involve dopamine receptor activity, and flu-like or generic withdrawal symptoms don’t specifically describe the sudden restoration of cholinergic signaling after removing a strong cholinergic blocker.