Butyrophenones

Question 1

What are butyrophenones used for?

Answer 1

sedation
Classified as antipsychotics

Question 2

What is the main butyrophenone used in vetmed?

Answer 2

azaperone, used primarily in wildlife and swine

Question 3

What is the MoA of a butyrophenone

Answer 3

• blockade of D2 dopamine receptors in mesolimbic-mesocortical pathways
• antagonism at D1, 5-HT, alpha1, and histamine

Question 4

How are butyrophenones metabolized and excreted?

Answer 4

in pigs - metabolized in liver and excreted in urine and feces

Question 5

Butyprophenone pharmacokinetics?

Answer 5

• onset after IM is ~10 min with peak effect ~30 min at 2mg/kg in pigs
• duration is 2-4 hours in pigs

Question 6

are there any toxic effects of butyrophenones?

Answer 6

No evidence-based known episodes

Question 7

What are the CNS effects of butyrophenones?

Answer 7

• sedation!! (mild to moderate in pigs)
• can cause extrapyramidal signs (rigidity, tremor, akinesia) at high doses

Question 8

What kind of CNS effects occur in horses?

Answer 8

paradoxical excitement

Question 9

What are the CV effects of butyrophenones?

Answer 9

blockage of alpha1-adrenergic receptors in vasculature which will lead to peripheral vasodilation and hypotension. duration of CV effects is longer than sedative effects with azaperone

Question 10

which has a higher affinity for the alpha1 receptor: acepromazine or azaperone?

Answer 10

acepromazine. however, azaperone results in less hypotension than acepromazine

Question 11

how much does CO/HR decrease in pigs after 2.5mg/kg azaperone IM?

Answer 11

20-40% decrease. arterial blood pressure decreases following azaperone administration and is NOT dose dependent

Question 12

What kind of respiratory effects are seen with butyrophenones?

Answer 12

• mild respiratory depressant effects in most species
• increases in respiratory rate and decreases in PaCO2 occur in pigs after 1-3.5mg/kg azaperone IM
• can see increased respiratory rates in rats and horses

Question 13

What are the musculoskeletal effects of butyrophenones?

Answer 13

• muscle relaxation d/t central effect as there is no activity at the neuromuscular junction
• good muscle relaxation

Question 14

Are there any known GI effects of azaperone?

Answer 14

No investigation at this time

Question 15

Are there any known urinary effects of azaperone?

Answer 15

No investigation at this time

Question 16

how does azaperone effect thermoregulation?

Answer 16

• antidopaminergic effect in thermoregulatory center in medulla
• altered basomotor tone in peripheral vessels decreases ability to retain heat

Question 17

how does zaperone have an antihistaminic effect?

Answer 17

demonstrated H1 receptor blockade

Question 18

How do butyrophenones effect hematocrit?

Answer 18

hematocrit reduction due to splenic sequestration and translocation of fluid d/t hypotension following administration of azaperone

Question 19

Should you give azaperone to horses?

Answer 19

No, probably not. Salivation, sweating, muscle tremors, and vocalization reported after administration IV in horses. Bizarre and violent behavior in horses after droperidol and azaperone noted

Question 20

will you see genitourinary side effects from butyrophenones?

Answer 20

• penile prolapse occurs in boars at dosages greater than 1 mg/kg IM, likely d/t secondary effect of vasodilation

Question 21

What is seen in dogs after butyrophenone IV administration?

Answer 21

muscle tremor, spasticity, and irritability

Question 22

Contraindications to butyrophenones?

Answer 22

should avoid in patient receiving selegiline (Anipryl) d/t increased risk of extrapyramidal effects