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Vasodilators
Control of vascular tone
27
Accounting
Pre-School
09/24/2009

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Term
vascular smooth muscle biochemistry
Definition
tone regulated by intracellular Ca2+,
Term
vasoconstriction pathways
Definition

2 independent receptor-mediated pathways

  1. a1 adrenergic - controls Ca channel activity via IP3; min to min regulation; small localized regions of control
  2. angiotensin II - tightly coupled to Ca channel; backup system for abnormal conditions; systemic
Term
vasodilatation biology
Definition
  • largely done by reduction in sympathetic tone
  • local = prostacyclin, adenosine, pH
  • systemic (coupled to EDRF) = bradykinin and ACh trigger NO release
  • Dopamine D1/D2
Term
pharmacologic targets to produce vasodilatation
Definition
  1. Ca channel
  2. Adrenergic receptors
  3. Dec angiotensin II synthesis or block receptors
  4. increase cellular NO
Term
arterial vasculature
Definition
high resistance vessels, control BP, 10% of blood volume, afterload
Term
venous vasculature
Definition
low pressure, high volume, control preload (contractility of heart); affected by postural changes
Term
Baroreceptor reflex
Definition

carotid sinuses

  • stretch receptors in wall of carotids and aortic arch
  • fall in BP increases sympathetic drive
Term
General uses for vasodilators
Definition
  1. HTN
  2. decrease afterload, even preload --> heart failure
  3. angina
Term
Alpha blockers (generally alpha 1b/d)
Definition
  • Prazosin - a1 blockade; ORAL; T1/2 3 hours
  • Doxazosin - same but 20 hour half life, lowers blood lipids
  • arterial system effects more pronounced
  • syncope is common
  • Useful for HTN, reduce afterload, and BPH
Term
ACE inhibitors
Definition
  • PROTOTYPE: captopril
  • prevent conversion of angiotensin I to II
  • more pronounced on arteries
  • reduces HTN, afterload
  • "kidney-sparing"
Term
Angiotensin II receptor (AT-1) antagonist
Definition

Losartan

  • about same anti-HTN as ACE inhibitors
  • contraindicated in pregnancy
Term
Aliskiren
Definition
  • renin inhibitor
  • decreases angiotensin II levels
  • similar efficacy to ACE or ARBs
  • may have a "rebound" effect
Term
Specific L-type Calcium channel blockers: uses, mechanism of action, prototypes
Definition

prototypes: nifedipine, diltiazem, felodipine, verapamil

  • minimize effects on heart while maintaining effects on vasculature
  • treat HTN and angina due to coronary artery spasm
  • all interact at different sites on L-type channel
  • greater effect on arteries than veins
  • Nifedipine and felodipine - cardio-sparing
  • Verapamil - strong cardiac effects
Term
specific L-type calcium channel blockers: pharmacokinetics and side effects
Definition

nifedipine, diltiazem, felodipine, verapamil

  • ORAL, long term therapy
  • nifedipine: sustaine release or short term
  • SE: headache and facial flushing, constipation, peripheral edema
Term
Nitroglycerine (organic nitrate): mechanism of action
Definition

metabolized and release NO in cells

  • NO increases cGMP thus ↑dephosphorylation, ↑K+ efflux; ↓Ca channel activity

affects venous circulation: ↓VR,preload,CO

Term
Nitroglycerine: pharmacodynamics
Definition
  • quite labile (keep cool), large first pass effect
  • given sublingual (acute angina), ointment, transdermal (prophylactic), and IV
  • virtually immediate effects but only for 15 min
Term
nitroglycerine: uses and side effects
Definition

Uses: coronary insufficiency, acute angina

SE: headache, hypotension, flushing/burning sensation

Term
Amyl Nitrate
Definition
  • organic nitrate
  • volatile liquid for INHALATION
  • very rapid onset (30 sec)
  • lasts 5 min
  • Used to diagnose murmur and angina
Term
isosorbide dinitrate
Definition
  • sugar nitrate
  • stable, ORAL, lasts 2-4 hours
  • given during nitrate-free holidays to ↓tolerance
  • angina prophylaxis and CHF
  • Mononitrate has longer half life but same effects
Term
sodium nitropusside
Definition
  • organic nitrate
  • ICU, emergencies to control arterial pressure, acute heart failure
  • extremely potent vasodilator
  • T1/2 30 sec, immediate onset, quick reversal
  • IV fusion
  • Tox: hypotensive crisis, accumulation of thiocyanate leading to CNS abnormalities limits use to 48-72 hours --> B12 reduces toxicity
Term
Arterial relaxants: names, mechanisms of action, and adverse reactions
Definition

Diazoxide, hydralazine, minoxidil

  • dilation of arterioles by increasing K+ efflux (hyperpolarizes)), reduces sensitivity to ATP
  • Baroreceptor reflex is adverse reaction
  • control w/ b-blocker or diuretic
Term
Diazoxide
Definition
  • arterial relaxant - opens K+ channels
  • IV: potent arterial vasodilator, inc CO
  • ORAL: blocks K+ secretion of insulin --> hyperglycemic effect
  • SE: profound hypotension
Term
Hydralazine
Definition
  • most used arterial relaxant
  • ORAL: combo w/ b-blocker, diuretic, captopril
  • treat HTN and CHF
  • acetylated by liver adn kidney
  • SE: lupus like syndrome
Term
Minoxidil
Definition
  • frequently used arterial relaxant
  • ORAL: activates K+ channels, ↑efflux
  • SE: hypertrichosis
  • used in combo with other drugs
Term
Pinacil
Definition
  • potent arterial vasodilator
  • requires less drugs in combination to control blood pressure
Term
Sildenafil
Definition

Phosphodiesterase Type V inhibitor

  • increased cGMP in corpus cavernosum
  • ORAL, 40 min onset, lasts 3-4 hours
  • Significant interaction w/ nitrates and a-adrenoceptor antagonists --> causes profound hypotension
Term
tadalafil
Definition
  • more selective phosphodiesterase type 5 inhibitor
  • lasts for 36 hours
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