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552 SecTioN iii Neurology aNd Special SeNSeS ` neurology—PhArmACology

Mixed agonist and antagonist opioid analgesics
drug meChAnism CliniCAl use notes
Pentazocine κ-opioid receptor agonist Analgesia for moderate to Can cause opioid withdrawal
and μ-opioid receptor weak severe pain. symptoms if patient is also
antagonist or partial agonist. taking full opioid agonist
(due to competition for opioid
receptors).
Butorphanol κ-opioid receptor agonist and Severe pain (eg, migraine, Causes less respiratory
μ-opioid receptor partial labor). depression than full opioid
agonist. agonists. Use with full opioid
agonist can precipitate
withdrawal. Not easily
reversed with naloxone.

Tramadol
meChAnism Very weak opioid agonist; also inhibits the Tramadol is a Slight opioid agonist, and a
reuptake of norepinephrine and serotonin. Serotonin and norepinephrine reuptake
CliniCAl use Chronic pain. inhibitor. It is used for Stubborn pain, but
can lower Seizure threshold, and may cause
AdVerse eFFeCts Similar to opioids; decreases seizure threshold; Serotonin Syndrome.
serotonin syndrome.

Glaucoma therapy  IOP via  amount of aqueous humor (inhibit synthesis/secretion or  drainage).
BAD humor may not be Politically Correct.
drug ClAss eXAmPles meChAnism AdVerse eFFeCts
β-blockers Timolol, betaxolol, carteolol  aqueous humor synthesis No pupillary or vision changes
α-agonists Epinephrine (α ),  aqueous humor synthesis via Mydriasis (α ); do not use in
1
1
apraclonidine, vasoconstriction (epinephrine) closed-angle glaucoma
brimonidine (α )  aqueous humor synthesis Blurry vision, ocular
2
(apraclonidine, brimonidine) hyperemia, foreign body
sensation, ocular allergic
reactions, ocular pruritus
Diuretics Acetazolamide  aqueous humor synthesis No pupillary or vision changes
via inhibition of carbonic
anhydrase
Prostaglandins Bimatoprost, latanoprost  outflow of aqueous humor via Darkens color of iris
(PGF )  resistance of flow through (browning), eyelash growth
2α
uveoscleral pathway
Cholinomimetics (M ) Direct: pilocarpine, carbachol  outflow of aqueous humor via Miosis (contraction of pupillary
3
Indirect: physostigmine, contraction of ciliary muscle sphincter muscles) and
echothiophate and opening of trabecular cyclospasm (contraction of
meshwork ciliary muscle)
Use pilocarpine in acute angle
closure glaucoma—very
effective at opening meshwork
into canal of Schlemm

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