Pyridostigmine is a cholinesterase inhibitor that increases acetylcholine levels at cholinergic synapses by reversibly blocking acetylcholinesterase enzyme activity. In the context of cluster headache treatment, it may modulate cholinergic neurotransmission and potentially reduce the frequency and intensity of headache attacks by influencing neuronal signaling pathways. Its use in cluster headache is considered off-label and based on limited clinical evidence.