Autonomic Agonists: Phenylephrine HCl, Dobutamine HCl and Mixed acting

What are the indications for Phenylephrine HCl?

Extra label for

-Low BP in cats and dogs

-Ascending colon displacement Horse

-Phacoemulsification - dog only

Why does Phenylephrine HCl work against Phacoemulsification?

It is an ophthalmic solution that causes Mydriasis w/ no accommodation loss

What is the pharmacodynamics of Phenylephrine HCl?

Direct acting A1 Agonist

How does phenylephrine HCl affect the vasculature?

Vasoconstriction of reservoir veins (a1 receptor Gq second messenger)

How does phenylephrine HCl affect the GI?

Relaxation

How does phenylephrine HCl affect the Respiratory system?

No effect

How does phenylephrine HCl affect the ocular system?

Mydrysis -Blocks canal of shlemm

Increase intraocular pressure

No accommodations

How does phenylephrine HCl affect the CV system?

Wont affect contractility or HR but will cause vascular pressure to grow down and will decrease the hr in response due to the Baroreceptors

How do we administer Phenylephrine?

IV/CRI, intraocular

Where is Phenylephrine excreted and how long is it effective?

Probably urinary

20mins after d/c

When would we use Phenylephrine practically?

Emergencies where we have already given atropine and fluids

To increase Cardiac patients that we don't want to increase CO via contractility or HR

What are adverse effects of Phenylephrine?

hypertension,

reflex bradycardia,

CNS stimulation,

necrosis,

What is a bizarre adverse effect of phenylephrine?

Hemorrhage in horses

What are contraindications for Phenylephrine?

Arrhythmia/ bradiacardia

Hypertension

Renal insufficency

Hepatic insufficiency

Elderly animals

Hyperthyroidism

Dobutamine is a non _____ labeled product and must be used _____ in _____ situations?

Veterinary drug

Extra label

ER

What is Dobutamine indicated use?

Short term tx of acute heart failure

What receptor will Dobutamine interact w/?

B1 (Drives heart increased contraction and HR) (sympathetic stimulation)

What systems will see no effect w/ usage of Dobutamine?

Vascular and respiratory

How will Doutamine affect the GI system?

Relax

How does Doutamine affect the GU system?

Increase renin and urine retention to increase BP - usually doesn't last long enough to see this

How does Doutamine affect the Ocular system?

Increases IPO via increased AQ humor production

Accommodation for far

NO mydriasis

How is Doutamine excreted?

Likely the urinary system.

2 minute 1/2 life (10 Minutes in the system)

What are the adverse effects of Dobutamine?

Tachycardia,

Chest pain

Arrhythmias

Seizures

What are contraindications of Doutamine?

Subaortic stenosis

Hypovolemia

Myocardial infarction

Arrhythmias

Hypersensitivity

What is the labeled use for Phynylpropanolamine? What is the extra-labled use

Urinary incontinence - dogs

extra-labels for Urinary incontinence in Cats

What is the pharmacodynamics of Phynylpropanolamine?

Mixed acting adrenergic agonist

- Directly on adrenergic receptors

- Induce NE release from Post-ganglionic neurons

Why would excessive dosing of Phynylpropanolamine cause Tachyphylaxis?

Would cause loss of NE stores in the neurons meaning we would not be able to use it to cause a bio-effect

How is Phenylpropanolamine administered and where does it get into?

PO

CNS

What is important about Phynylpropanolamine metabolism and elimination?

Metabolism - active metabolite produced

Eliminated - urine 1/2 life of 3hrs

What are adverse effects of Phynylpropanolamine ?

CNS stimulation

Urine retention

Tachycardia

Hypertension

What are contraindications of Phynylpropanolamine?

Glacoma

Prostatic hypertorphy

Hyperthyroidism

DM

CV disorders

Kidney insufficiencies

Hypertension

All uses of Ephedrine sulfate are?

Extra label

What are indications of Ephedrine sulfate?

Hypotension in anesthesia - (dogs cats horses)

Urinary incontinence in dogs and cats (NOT COMMON)

Ephedrine sulfate has the same pharmacodynamics as which drug?

Phynylpropanolamine

How is Phynylpropanolamine elimination different from Ephedrine sulfate?

Ephedrine sulfate is a basic drug and pH of urine is going to determine the half life of the drug