why is phenylephrine used for dilation over physostigmine or pilocarpine?

Answer:
Both physostigmine and philocarpine are parasympathomimetics (mimic the parasympathetic nervous system). This can lead to bradycardias (slow heart rates) and excessive lacramentation (tearing of the eyes). Phenylephrine is an alpha agonist (alpha receptors of the sympathetic nervous system) and causes local vasoconstriction and mydriasis (dilation of the pupil). Phenylephrine is also a common nasal decongestant. There are better medications for mydriasis than any of the above.

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