Sympatholytics Flashcards
A ______ alpha blockade that has been established cannot be reversed by sympathomimetics. The effects are terminated by _____.
Phenoxybenzamine; metabolism
Induced alpha receptor blockade permits enhanced neural release of _____ causing an ______ HR & CO
NorEpi; increased
Phentolamine
Nonselective alpha antagonist
Peripheral vasodilation and decreased BP w/in 2 min lasting 10-15 min
Used for hypertensive emergencies like w/ pheochromocytoma
30-70 mcg/kg (1-5 mg); continuous inf 0.1-2mg/min
Can be used for extravasation of sympathomimetic
Onset of blockade of Phenoxybenzamine
Slow up to 60 min to peak
Phenoxybenzamine produces little changes in systemic BP in the ____ patient in the absence of _____
Normovolemic; increased SNS activity
If given during maternal treatment can cause neonatal hypotension and resp distress in first 72 hrs of life
Phenoxybenzamine
Withdrawal of alpha 2 agonists even after short term use can result in rebound effect causing dramatic increase in sympathetic outflow causing?
Elevated HR and HTN to dangerous levels
Dexmedetomidine
Selective alpha 2 agonist 1,600:1
IV 0.1- 1.5 mcg/kg/min
H/l: 2 hrs
Extensive bio transformation in liver, E in urine
Potent binding & short half life can induce physiologic dependence resulting in withdrawal phenomenon (tachy, HTN, anxiety)
What determines if a beta drug acts as an agonist or an antagonist?
Substitutions on the benzene ring
Beta 1 receptor blockade:
Slows sinus rate
Slows conduction of cardiac impulses through AV node
Decreases inotropy
Among the beta adrenergic receptor antagonists, what is the only drug that is highly plasma protein bound?
Propranolol (90-95%)
Volume of distribution of beta adrenergic receptor antagonists is ____ and are _____ distributed following IV admin.
High; rapid
Why is Nadolol unique?
It’s long duration of action permits once daily administration
(H/t: 20-40 hrs)
How is timolol effective in treatment of glaucoma?
Its ability to decrease IOP presumably by decreasing production of aqueous humor
Protein binding of timolol
Not extensive
What is the systemic issue with timolol?
Administered as eye drops but systemic absorption may be sufficient to cause resting bradycardia and increased airway resistance
Prominent pharmacologic effect of Bisoprolol
Negative chronotropic effect
How does betaxolol compare with timolol in bronchoconstriction
Risk of bronchoconstriction in pts with airway hyper reactivity is less than with timolol
Typical initial dose of ___ IV of Esmolol over about 60 sec with a full therapeutic effect evident within ____ min
Action ceases in approximately _____ min after adm stopped
0.5mg/kg; 5 min
10-30 min
Although ____ & ____ may be used to blunt increase in SBP associated with laryngoscopes and tracheal intubation, neither influences ___
Fentanyl, lidocaine, HR
what drug in the presence of inhaled anesthetics may cause profound bradycardia?
Timolol
Additive CV effects with inhaled anesthetics and B-blockers:
Greater with Enflurane
Least with Isoflurane (Sevo & Des do not seem to be associated with sig additive effects either)
Goal HR of preop B-blocker therapy
65-80
Max SBP lower effect of an IV dose of Labetalol ____ is present in _____ min
0.1-0.5mg/kg; 5-10 min
