What are butyrophenones used for?
sedation
Classified as antipsychotics
What is the main butyrophenone used in vetmed?
azaperone, used primarily in wildlife and swine
What is the MoA of a butyrophenone
- blockade of D2 dopamine receptors in mesolimbic-mesocortical pathways
- antagonism at D1, 5-HT, alpha1, and histamine
How are butyrophenones metabolized and excreted?
in pigs - metabolized in liver and excreted in urine and feces
Butyprophenone pharmacokinetics?
- onset after IM is ~10 min with peak effect ~30 min at 2mg/kg in pigs
- duration is 2-4 hours in pigs
are there any toxic effects of butyrophenones?
No evidence-based known episodes
What are the CNS effects of butyrophenones?
- sedation!! (mild to moderate in pigs)
- can cause extrapyramidal signs (rigidity, tremor, akinesia) at high doses
What kind of CNS effects occur in horses?
paradoxical excitement
What are the CV effects of butyrophenones?
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
which has a higher affinity for the alpha1 receptor: acepromazine or azaperone?
acepromazine. however, azaperone results in less hypotension than acepromazine
how much does CO/HR decrease in pigs after 2.5mg/kg azaperone IM?
20-40% decrease. arterial blood pressure decreases following azaperone administration and is NOT dose dependent
What kind of respiratory effects are seen with butyrophenones?
- 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
What are the musculoskeletal effects of butyrophenones?
- muscle relaxation d/t central effect as there is no activity at the neuromuscular junction
- good muscle relaxation
Are there any known GI effects of azaperone?
No investigation at this time
Are there any known urinary effects of azaperone?
No investigation at this time
how does azaperone effect thermoregulation?
- antidopaminergic effect in thermoregulatory center in medulla
- altered basomotor tone in peripheral vessels decreases ability to retain heat
how does zaperone have an antihistaminic effect?
demonstrated H1 receptor blockade
How do butyrophenones effect hematocrit?
hematocrit reduction due to splenic sequestration and translocation of fluid d/t hypotension following administration of azaperone
Should you give azaperone to horses?
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
will you see genitourinary side effects from butyrophenones?
- penile prolapse occurs in boars at dosages greater than 1 mg/kg IM, likely d/t secondary effect of vasodilation
What is seen in dogs after butyrophenone IV administration?
muscle tremor, spasticity, and irritability
Contraindications to butyrophenones?
should avoid in patient receiving selegiline (Anipryl) d/t increased risk of extrapyramidal effects
