Pharmacology Flashcards

Opioid-induced nausea and vomiting occurs primarily through stimulation of which brain region?

Answer: Chemoreceptor trigger zone (CTZ) in the area postrema

Opioids stimulate dopaminergic and serotonergic receptors in the area postrema chemoreceptor trigger zone, activating the vomiting center.

Which drug class interaction is the basis of serotonin syndrome risk when combining certain pain medications?

Answer: Serotonin-increasing drugs (SSRIs, MAOIs, meperidine) combined causing serotonergic excess

Serotonin syndrome results from excessive serotonergic activity - combining SSRIs, MAOIs, meperidine, tramadol, or triptans increases serotonin to toxic levels.

A ceiling effect for analgesia at higher doses is a characteristic of which drug class?

Answer: Partial mu-opioid agonists (buprenorphine)

Partial agonists like buprenorphine produce a ceiling analgesic effect - beyond a dose threshold, increasing the dose adds no further analgesia but does increase side effects.

The anticholinergic drug atropine, when given for emergency bradycardia, works by:

Answer: Blocking muscarinic receptors, removing vagal inhibition of SA node automaticity

Atropine blocks cardiac muscarinic (M2) receptors, preventing vagal acetylcholine from slowing the SA node, thereby increasing heart rate.

Nitrous oxide diffuses into closed gas-containing body spaces faster than nitrogen exits because:

Answer: Nitrous oxide is approximately 34 times more blood-soluble than nitrogen, allowing rapid diffusion

N2O high blood-gas solubility coefficient means it transfers rapidly from blood into gas-filled spaces, expanding them. This is why N2O is contraindicated with bowel obstruction, pneumothorax, and middle ear surgery.

Which property of a local anesthetic determines how quickly it produces nerve block onset?

Answer: pKa relative to tissue pH (proportion of unionized form available to diffuse through nerve membrane)

Lower pKa means a greater proportion of the drug is in the unionized (lipid-soluble) form at tissue pH 7.4, allowing faster membrane penetration and faster onset.