Find a drug that influences neurotransmitter signaling. Which neurotransmitter system is impacted by the drug

Find a drug that influences neurotransmitter signaling.
Which neurotransmitter system is impacted by the drug?
Does the drug influence a specific receptor sub-type? Is the drug primarily an agonist or antagonist?
What is the drug marketed to treat? Are there side effects of the drug related to its mechanism of action?