Premedication drugs Flashcards
What is the mechanism of the Phenothiazine class of pre-meds? Can you give examples of Phenothiazines?
Mechanism: Dopamine Antagonists
E.g. Acepromazine, Promethazine
What affects does Acepromazine have on the CNS, GI, Resp and CVS?
CNS - Anti-pyschotic, sedative, calming esp in young
GI - anti-emetic via. CTZ antagonism
CVS - Peripheral vasodilation and anti-arrhythmic. (CARE: Hypothermia, decrease BP)
Resp - little or no effect.
How can ACP be given? What is it’s time to onset?
IM/IV routes, also oral. 20-30 mins onset.
What are the contraindications for ACP?
Hypotension/shock, Boxers, Brachycephalics, Valuable breeding stallions, intradermal skin tests (due to anti-histamine), CVS disease, seizures.
What is the mechanism of the Butyrophenones class of pre-meds? Can you give examples of Butyrophenones?
Mechanism: Dopamine Antagonism
E.g. Azaperone, Fluanisone, Droperidol.
What affects does Azaperone have on the CNS, GI and CVS?
CNS - sedation
GI - anti-emetic
CVS - some vasodilation, some hypotension
What is the main use of Azaperone? How is it administered? What is it important to do once dose is given?
Sedate pigs. Preffered deep IM in neck. Must be left undisturbed for 30 mins after dose.
What is the mechanism of Alpha-2 receptor agonists?
Activation of presynaptic A2 receptors causes a decrease in NAd. Activation of post-synaptic A2 receptors causes PERIPHERAL VASOCONSTRICTION. (A1 response)
Can you give some examples of Alpha-2 agonists?
Xylazine, Detomidine (Domosedan), Romifidine (Sedivet), Metomidine (Domitor), Dexmetotomidine (Dexdomitor)
How do Alpha 2 agonists affect the CNS?
Vagally mediated bradycardia (try decrease BP due to vasoconstriction), clasically hypertension, then hypotension, then normotension.
How do Alpha 2 agonists affect the Resp?
Depression, esp in ruminants
How do Alpha 2 agonists affect the GIT?
Vomiting in dogs and cats, depressed motility.
How do Alpha 2 agonists affect the Endocrine system?
Inhibition of ADH promotes diuresis, inhibits insulin causing hyperglycaemia (and this osmotic diuresis)
How do Alpha 2 agonists affect the Urogenital system?
Uterine contraction - not given in pregnancy unless absolutely necessary.
How is Xylazine administered? What is it’s selectivity for A2 receptors like?
IM or IV. Duration variable in species. Low selectivity for A2r, so affects A1r also.
What are the contraindications for Xylazine?
Hypotension, animals with cardiac disease
How is Detomidine (Domosedan) administered? What species is it used in? What is it’s selectivity for A2 receptors like?
IV or IM. It is used in horses and cattle. Greater A2 selectivity than Xylazine.
How is Romifidine (Sedivet) administered? What species is it used in? Why is it good for standing orthopaedic or in mares with foals?
IV or IM. It is used in horses. It is good because it causes less ataxia, so she doesn’t fall on foal.
What are the main uses of Metomidine (Domitor) and Dexmetomidine (Dexdomitor)?
Best reserved for young, healthy animals. Useful in aggressive/overexcited cats/dogs.
Can you name some alpha-2 adrenoreceptor ANTAGONISTS?
Antipazmezole (Antisedan) - used to reverse metomidine and dexmetomidine.
What is the mechanism of Benzodiazepenes? Can you give some examples of Alpha-2 benzodiazapenes?
Mechanism: Potentiation of GABA (inhibitory signals)
E.g. Diazepam, Midazolam, Diazemuls
How do benzodiazepenes affect the CNS? How do they affect the CVS/Resp?
CNS - primarily anxiolytic, muscle relaxant and anti-convulsant.
CVS/Resp - Minimal depression
How is Diazepam administered? Why do you have to be careful when drawing it up too early? What drugs inhibit it’s metabolism?
IV, oral or rectal. It is absorbed onto plastic so don’t draw up too early. Metabolism inhibited by cimetidine.
What are the contraindications for diazepam?
Hepatic Encephalopathy, be careful in cats on oral diazepam as can cause hepatic failure, Caution in excited/viscous as has variable sedation.
What are anti-cholinergic drugs used for? Can you give some examples? Which is the drug of choice in rabbits?
Increase HR, reduce salivation, reduce gut motility, dilate pupil, relax bronchi e.g. Atropine, Glycopyrrolate (rabbits).
