ICAR AICE-JRF/SRF Veterinary Neuropharmacology: practice questions

Question 1 · hard

Ketamine at subanaesthetic infusion rates is used as an analgesic adjunct mainly because it:

1. Blocks NMDA receptors involved in dorsal-horn central sensitisation (wind-up)
2. Activates mu opioid receptors (as morphine does) in the periaqueductal grey and the spinal dorsal horn
3. Blocks cyclo-oxygenase-2 in inflamed tissue
4. Opens GABA-A chloride channels in the spinal cord

Question 2 · hard

A sheep sedated with an alpha-2 agonist becomes hypoxaemic. The mechanism most often reported is:

1. Methaemoglobinaemia
2. Pulmonary interstitial oedema and intrapulmonary shunting
3. Bronchoconstriction from histamine release by pulmonary mast cells
4. Airway obstruction by the soft palate

Question 3 · hard

Tiletamine-zolazepam gives a rough, tiletamine-dominated recovery in dogs but a calmer recovery in cats. The explanation is:

1. Dogs lack GABA-A receptors in the cortex
2. Cats metabolise both components faster than dogs, so neither drug outlasts the other
3. In dogs zolazepam is cleared before tiletamine; in cats tiletamine is cleared first
4. Tiletamine is inactive in cats

Question 4 · hard

Approximately what fraction of absorbed halothane is metabolised, compared with isoflurane?

1. About 0.2% for halothane versus 20–25% for isoflurane
2. About 50% for both
3. About 20–25% for halothane versus about 0.2% for isoflurane
4. Less than 0.01% for both

Question 5 · hard

Lidocaine has a pKa of 7.9. Using Henderson-Hasselbalch, what fraction is un-ionised at pH 7.4 and at pH 6.9?

1. About 76% at pH 7.4 and about 91% at pH 6.9
2. About 24% at pH 7.4 and about 9% at pH 6.9
3. About 50% at both pH values
4. About 9% at pH 7.4 and about 24% at pH 6.9

Question 6 · hard

Tramadol provides inconsistent analgesia in dogs. The main pharmacokinetic reason proposed is:

1. Dogs lack mu opioid receptors
2. Tramadol is not absorbed orally in dogs, so blood levels are always negligible
3. Dogs produce little O-desmethyltramadol, the active mu-agonist metabolite
4. Dogs convert tramadol entirely to morphine

Question 7 · hard

A dog received buprenorphine 1 hour ago but is still painful after surgery. Why may giving a full mu agonist now be less effective than expected?

1. Buprenorphine's high receptor affinity limits binding of the full agonist
2. Buprenorphine has irreversibly destroyed the mu receptors in the dorsal horn
3. Full agonists are inactive after any partial agonist
4. The full agonist will be metabolised to buprenorphine

Question 8 · hard

The half-life of phenobarbital in a dog is 48 hours. About how long after starting a fixed daily dose (without loading) is steady state reached, and what fraction of steady state is present after 3 half-lives?

1. About 10 days; about 87.5%
2. About 2 days; about 50%
3. About 10 days; about 75%
4. About 30 days; about 97%

Question 9 · hard

During a non-depolarising neuromuscular block, train-of-four stimulation shows:

1. Four equal but reduced twitches without fade, as seen with succinylcholine
2. Post-tetanic depression only
3. Increased twitch height (facilitation)
4. Fade, with progressively weaker twitches from the first to the fourth

Question 10 · hard

Which non-depolarising blocker is long-acting and vagolytic, tending to raise heart rate?

1. Atracurium
2. Cisatracurium
3. Pancuronium
4. Rocuronium