Which of the following medications are NOT considered Dopamine agonists (adrenergic agonists)?

• A. Methylphenidate
• B. Dextroamphetamine
• C. Neostigmine
• D. Bromocriptine

Answer: (C)

Dopamine agonists work by either directly stimulating dopamine receptors or by boosting dopamine signaling in the brain. Bromocriptine is a direct dopamine receptor agonist, meaning it mimics dopamine at its receptors (notably D2) and is used in conditions like Parkinson’s disease and hyperprolactinemia.

Methylphenidate and dextroamphetamine increase dopaminergic activity, but not by directly activating the receptors. They elevate synaptic dopamine levels—methylphenidate by blocking reuptake and dextroamphetamine by promoting release—leading to enhanced dopaminergic transmission, which classifies them as indirect dopamine agonists.

Neostigmine, on the other hand, is a cholinesterase inhibitor. It increases acetylcholine at cholinergic synapses and does not stimulate dopamine receptors or boost dopaminergic signaling, so it is not a dopamine agonist.