CV Drugs II Flashcards
Ephedrine Class
- NT Releaser
- Alpha- & Beta-Adrenergic Receptor Agonist
Ephedrine MOA
- direct –> acts directly at alpha and beta adrenergic receptors to create effect
- indirect –> acts to increase the amount of NT released (specifically NE)
Ephedrine PK/PD
DOA: 15-60 min
-DOA prolonged in elderly
Ephedrine Dose/Route
IV bolus: 0.1-0.2 mg/kg OR 5-25 mg
*can give in 5 mg increments
Ephedrine Clinical uses
hypotension
Ephedrine Effects/Considerations
can cause tachyphylaxis which depletes stores of catecholamines with repeated doses
Phenylephrine Class
Alpha Adrenergic Agonist
Phenylephrine MOA
- direct acting only
- binds to the alpha adrenergic receptor and exerts same effect as endogenous catecholamine
Phenylephrine PK/PD
DOA: 5-10 min
Phenylephrine dose/route
IV bolus: 50-200 mcg
IV infusion: 20-100 mcg/min
Phenylephrine clinical uses
- hypotension
- nasal intubation or NP tube placement as nasal spray to vasoconstrict –> decrease bleeding risk
Alpha Adrenergic Antagoinst Drugs
Phentolamine
Prazosin
Yohimbine
Phenoxybenzamine
Alpha Adrenergic Antagoinst MOA
- bind selectively to alpha receptors and interfere with ability of catecholamines to cause a response
- phentolamine, prazosin, yohimbine = competitive antagonism
- phenoxybenzamine = covalent bond
Alpha Adrenergic Antagoinst clinical uses
- HTN
- BPH (benign prostatic hypertrophy)
- pheochromocytoma (non-selective agents)
Alpha Adrenergic Antagoinst effects/considerations
CV Effects:
-alpha 1 –> decreased PVR, decreased BP, postural hypotension (d/t failure of venoconstriction upon standing
-alpha 2 –> increases NE release from nerve terminals, resultant tachycardia from stimulation of beta receptors
GU effects – blockade in prostate and bladder cause muscle relaxation and ease micturition
-miosis
-increased nasal congestion
Phenoxybenzamine Class
Non-selective Alpha-Adrenergic Antagonist
Phenoxybenzamine MOA
- covalent bond to alpha receptor
- non-selective but higher affinity for alpha 1 vs alpha 2
Phenoxybenzamine PK/PD
-pro-drug (i.e., inactive until something in body activates it
Onset: 1 hour
E1/2: 24 hrs
Phenoxybenzamine Dose/Route
PO: 0.5-1.0 mg/kg (preop for BP control for pheo)
Phenoxybenzamine Clinical Uses
- preop for patients with pheochromocytoma (PO)
- potential use for patients with Raynaud’s
Phenoxybenzamine Effects/Considerations
- decreased SVR, vasodilation
- less tachycardia (due to less alpha2)
Phentolamine Class
Non-selective Alpha-Adrenergic Antagonist
Phentolamine MOA
non-selective, equal affinity for alpha1 and alpha2
Phentolamine Dose/Route
IV: 30-70 mcg/kg
SubQ: 2.5-5 mg
Phentolamine Clinical Uses
- intraoperative management of HTN emergencies (Pheo manipulation or autonomic hyperreflexia)
- extravascular admin of sympathomimetic agents (subQ to minimize necrosis)
Phentolamine Effects/Considerations
- peripheral vasodilation and a decrease in SVR
- reflex mediated and alpha2 associated increase in HR and CO
Prazosin Class
Selective Alpha1-Adrenergic Antagonist
Prazosin MOA
selective for alpha1
Prazosin Clinical Uses
- preop prep for pheo
- essential HTN (in combo with thiazides)
- decrease afterload in pt with HF
- Raynaud phenomenon
Prazosin Effects/Considerations
- less likely to cause tachycardia
- dilates both arterioles and veins
Yohimbine Class
Selective Alpha2-Adrenergic Antagonist
Yohimbine MOA
- selective for alpha 2
- higher affinity for alpha2 vs alpha1
- increases release of NE from post-synaptic neuron
Yohimbine Clinical Uses
- orthostatic hypotension
- impotence
Terazosin & Tamsulosin Class
Selective Alpha1-Adrenergic Antagonist
Terazosin & Tamsulosin MOA
long acting selective alpha 1a