T3 Flashcards
phenylephrine
selective a1 rec
raises BP like NE–>more ref. brady
correct neurogenic shock, use during therap. spinal and other anesthesia
do not stimulate heart
phenyephrine local uses
hemorrhoids
nasal congestion
mydriatic agent
supraventricular tachycardias (IV)
midodrine
newer than phenyleprine
prodrug, “smoother absorbtion”
othostatic hypotension, urinary incontinence
–counterindicated for HTN pts.
oral absorption of phenylephrine is..
poor, midodrine is better
cocaine
inhibits reuptake of NE at symp. nerve terminals
- good LOCAL anesthetic, topical, local mucous membranes and for intubation of trachea through the nose
- constricts BVs at site, drug stays at site
- rarely for pain relief and redusing epistaxis while nose intubation
- CNS effects: abuse
psuedoephiedrine and ephedrine
stimulate rel. of NE from symp. nerve endings independent of nerve APs
–>stim. adrenergic rec. directly
psuedoephiedrine and ephedrine tx
nasal and bronchial congestion–>promotes nasal and sinus drainage
amphetamine, methamphetamine, methylphenidate
stim. rel. of catechols from symp. and central nerve endings
- concern is central effects
pharmkin considerations: selective a1, B2, B3 direct acting agonists and ind. acting drugs
readily absorb, tx effective after oral admin, action last for hours
pharmkin considerations: cocaine (and some other direct-acting agonists: NE, E, Isoproterenol, DA, Dobutamine))
must be given parenterally(IV, inhalation) to be effective tx and actions last only few min if given IV
*last longer if whole tissue injection: oral mucosa, skel. musc
tolerance in sympathomimetic drugs
recepters down regulate when exposed chronically
ex: DA or dobutamine for CHF pts., chronic nasal congestions w. pseudoephed., bronchoconstr in asthmatics w. sel B2 agonists (oral typ worse than inhaled)
rebound phenomena
symptoms you were attempting to tx return “with a vengeance”
side effects of symp. agonists
gen. extension of tx effects
lack of suff. rec. selectivity
CNS side effects
*worse when dose is higher
sympathomimetic side effects examples
tx dep. cardiac contractility after MI w. B agonist–>stim B rec.–>lead to more O2 deficite, tachy, arrhy
- attempt to prevent hypotension w/ NE–>HTN
- local dermal tiss. necr. when IV inf of a agonist for systemic tx ends up in surrounding tissue
- tx urine incontinence/ortho. hypotension w/ midodrine–>a-1 mediated piloerection and bladder urine retention
symp. drugs SE: lack of suff. rec selectivity
- attempt to prev. premature labor w/ terbutaline (B2 rec) ending up w/ tachy in both mother and fetus (all cardiac B rec)
- inha. albuterol for asthma–>B2s AND B1 stim–>arrhythmias
- DA to inc. renal blood flow–>went to high–>stim. a1 rec–>offset vasodilation
side effects: CNS
mainly seen w. indirect acting sympathomimetics (dir. less likely to enter brain, exc: nervousness from epinephrine (pt. “sensing” drug, not nec. CNS effect)
i.e. insomnia, anxiety, convulsions, agitation, hallucinations, etc)
B-Blockers
Acebutolol (Sectral)
Atenolol (Tenormin)
Exmolol (Brevibloc)
Metoprolol (Lopressor, Toprol-XL)
Nadolol* (Corgard)
Pindolol* Propranolol* (Inderal-LA) Timolol* (Timoptic) *B1 AND B2 rec selectivity ALL inhib B1
intrinsic sympathomimetic action (ISA) of B blockers
partial agonist effect
*can never deliver so much drug to completely shut down receptors
(in general: rev. competitive antagonists)
B blockers partial agonists
Acebutolol
Pindolol
B blockers membrane stability (“local anesthetic” action)
acebutolol
metoprolol?
pindolol?
propranolol
B blocker lipid solubility
L: others
M: metoprolol, pindolol
H: propanolol
-low: no liver inactivation but direct excretion thru kidney EXCEPT Esmolol: Low, but inactivated by circulating esterases (short duration)
-high: more likely to enter brain and be cleared by liver
B blockers: B1
by inhib. B1 rec: all B blockers can dec. most symp. supported cardiac fund (dec. HR, contract, automat, conduction velocity)
antiangina use of B blockers
–>by dec. HR and contract, can dec myocardial O2 deficit that causes angina inputs w/ poor coronary O2 deliver (atheroscl)
B blocker: anti-HTN
lower HTN by dec. rate and contractility, also dec renin sec (B1) in kidney JG cells
B blocker: prevent post-MI arrhythmias
dec. automaticity in potential cardiac pacemaker cells (in extraneous (non-SA) pacemaker cells)
- slow/inhibit automaticity (AV node, purkinje rec, wall of ventricles) can slow down conduction thru ventricles: prevent supraventricular arrythmias
B blockers: protect heart from
dangerous catecholamine-ind. tachys and arrhythmias during:
- surg. removal of pheochromocytomas (NE, E release)
- “thyroid storm” in hyperthyroidism: exc. catecholamine ACTION (not nec. presence) in heart
what about B2 blockers??
do not want to inhibit vasodilation, alpha rec. would then be uninhibited–>vasoconstrictor
B2 blockers
- tx for glaucoma: dec. AH production in ciliary epithelium to lower IOP
- timolol (Timoptic): no membrane stabilizing, unless v. high dose (“local anesthetic action”, good!) if - undesirable in eye–>could lead to eye damage
what about Nadalol? (non mem stab, B2) -low lipid solubility, would need systemic dose
unlike nonsel. B blockers w.out ISA (partial agonist activity), those WITH ISA (pindolol) do not interfere w.
B2-mediated relaxation of vessels in skeletal muscles
–>can actually enhance such relaxation enough to dec. TPR–>overall antiHTN mech (“vasodilator” B-blockers), further enhancement of lowering BP
membrane stabilization may have..
antiarrhythmic props. but at such high doses, not commonly used (propranolol)
high Lipid solubility
may enter brain: potentially beneficial CNS-rel. CV actions (lowering BP)
-inactivated by liver, req. good liver fund.
low lipid solubility
req. good RENAL function–>inactivated by renal excr.
* lipid sol. det. drug choice for certain pts.
this drug has shortest duration due to rapid inactivation by circ. esterases (10 min)
Esmolol: used only IV to control critical, acute CV conditions (HTN, MI, SV arrhythmia post-surg) want only temporarily
longer acting B blocker (24 hr duration)
Nadolol: for chronic conditions where pt. compliance is important
other nonspecific actions of B blockers
- migraine and “stage fright”
- heart failure?? (CI!: not well understood but true)
B1 blocker side effects: excess depression of cardiac B1 rec
sinus brady, AV blockade, depressed CO–>Raynaud’s and intermittent claudication, exercise intolerance (phys. active pts)
B2 blocker side effects
- bronchoconstriction (or spasm) in asthmatics due to inhib. of B2 med. relax. of airways
- intermittent claudication and exer. intolerance (no B2 vasodilation)
- delayed recovery from insulin-induced hypoglycemic episodes (dec. B2 med hep. glucose output)
partial agonist activity B blockers
potentially same side effects but less severe (understandably w/ agonist activity)