Final answer:
Pinpoint fixed pupils often suggest the use of pilocarpine, a drug that treats eye disorders by affecting muscarinic receptors, causing pupil constriction, and facilitating the drainage of aqueous humor to lower intraocular pressure.
Step-by-step explanation:
The presence of pinpoint fixed pupils can suggest the use of a substance that affects the muscarinic receptors within the eye. A common drug associated with causing pinpoint pupils, or miosis, is pilocarpine, a nonspecific muscarinic agonist used in treating eye disorders. Pilocarpine works by reversing mydriasis which is commonly induced by phenylephrine during an eye examination. The action of pilocarpine involves constricting the pupil via the smooth muscle of the iris and contracting the ciliary muscle.
This allows for better drainage of aqueous humor from the anterior compartment of the eye, thus reducing intraocular pressure in glaucoma patients. The symptoms associated with pilocarpine use or exposure to other muscarinic agonists can include not just pinpoint fixed pupils but also blurred or dim vision, headache, nausea, vomiting, diarrhea, excessive secretions or sweating muscle twitching or fasciculations, dyspnea, seizures and unconsciousness.