PostMT, Vasodilators and Sympathetics Flashcards
What are three vasodilators (NO modulators) that release NO from drug or endothelium? When are they each used clinically?
Nitroprusside, used in HTN emergencies
Nitrates, used in HTN emergencies and angina
Hydralazine, used in long term outpatient therapy of severe or resistant HTN
What are four vasodilators that reduce calcium influx (Calcium Channel Blockers). When are they all clinically used?
Verapamil, Diltiazem, Nifedipine, Amlodopine.
Used in long term outpatient therapy of HTN, HTN emergencies, and angina.
What are two vasodilators that cause hyperpolarization of smooth muscle membrane through opening of potassium channels (potassium channel openers)? When are is each used clinically?
Minoxidil, used for long term outpatient therapy of severe or resistant HTN.
Diazoxide, used for HTN emergencies.
What is a vasodilator that activates dopamine receptors? When is it used clinically?
Fenoldopam, used in HTN emergencies.
Two major subclasses of Calcium Channel Blockers. Two examples of each.
What do CCBs block?
DiHydroPyridines. Nifedipine and Amlodipine
Non-DiHydroPyridines. Verapamil and Diltiazem.
CCBs block L-type VCCC.
MOA of DHPs
Block L-type calcium channels in VASCULATURE > cardiac channels.
Not as large an effect on cardiac muscle as non-DHPs; but they block smooth muscle at much lower concentrations, so cardiac effects are negligible at effective therapeutic concentrations.
MOA of non-DHPs
Nonselective block of VASCULAR AND CARDIAC L-type calcium channels.
non-DHPs have MORE CARDIAC EFFECT THAN DHPs!
Why do DHPs and non-DHPs differ in effects on vascular v. cardiac tissues?
While all CCBs bind to L-type calcium channels, DHPs and non-DHPs bind to DIFFERENT SITES on the channel proteins.
CCB (DHP primarily) effects on smooth muscle.
VASODILATION, which decreases peripheral resistance, arterioles are more sensitive than veins, orthostatic hypotension not usually problem.
RELAXATION of arteriolar smooth muscle leads to decreased afterload and decreased oxygen demand by the heart.
CCB (non-DHP primarily) effects on cardiac muscle
Reduced contractility, decreased SA node pacemaker rate, decreased AV node conduction velocity.
General MOA of vasodilators used for HTN.
Relax smooth muscle of arterioles, decreasing the peripheral vascular resistance and thus, the arterial blood pressure; sodium nitroprusside and the nitrates also relax veins.
In what form are all CCBs active?
Orally
What 4 CCBs can be administered by IV, as well as orally?
nifedipine, clevidipine, verapamil, diltiazem
What CCB has the longest half life?
Amlodipine, 35-50 hours
Adverse effects of DHPs
Excessive hypotension Dizziness HA Peripheral edema Flushing Tachycardia Rash Gingival Hyperplasia
What is a contraindication for use of nifedipine?
Don’t use in patients with chronic HTN
Nifedipine is a SHORT acting DHP and has increased risk for MI, stoke, death.
What should be used for treatment of chronic HTN?
SLOW RELEASE and long acting DHPs.
Adverse effects of non-DHPs.
*Constipation with Virapamil
* peripheral edema
Dizziness, HE, AV block, bradycardia, heart failure.
Lupus-like rash with Diltiazem
Pulmonary edema, coughing, wheezing possible.
*When are non-DHPs contraindicated?
**When a person is also taking a BETA-BLOCKER.
Non-DHPs (verapamil>diltiazem) slows HR, can SLOW AV CONDUCTION, can cause heart block.
When should nifedipine be used?
Use in the presence of AV conduction abnormalities because it does not slow AV conduction.
CCBs are not indicated for use in what?
But which 2 can be used if necessary for another indication? What indication?
HF
Amlodipine and felodipine can be used for indicated angina or HTN because of their relatively neutral vasoselective effects.
What drug-drug interaction can verapamil have with digoxin?
Increase digoxin levels through phrmacokinetic interaciton.
What drug-drug interaction do DHPs have?
What drug-drug interaction do non-DHPs have?
Additive with other vasodilators.
Additive with other cardiac depressants and hypotensive drugs.
What are the clinical uses of CCBs?
Long term outpatient therapy of HTN (counteract reflex CV responses)
HTN emergencies
Angina
Potassium Channel Openers
Diazoxide
Minoxidil
Diazoxide and Minoxidil MOA
Opens potassium channels in smooth muscle.
Diazoxide and Minoxidil Pharmacodynamics (2).
(1) Increasing potassium permeability that hyperpolarizes smooth muscle membrane, reducing probability of contraction.
(2) Arteriolar dilator, resulting in reduced systemic vascular resistance and mean arterial pressure. (minoxidil does NOT dilate veins)
Diazoxide Pharmacokinetics (3).
(1) Relatively long acting (4-12 hours after injection).
(2) High protein binding - metabolism not well understood
(3) Administered as 3-4 injections, 5-15 min apart, prn. Sometimes by IV
Diazoxide:
- Adverse effects
- Contraindications
- Excessive hypotension resulting in stroke and MI. Hyperglycemia in patients with renal insufficiency
- Contraindicated in patients with ischemic heart disease - increases propensity for angina, ischemia, cardiac failure.
How should dosing of diazoxide be changed in a patient with renal failure or pretreated with beta blockers to prevent reflex tachycardia?
Smaller doses because hypotensive effects are greater in theses patients.
Minoxidil Adverse Effects/Contraindications
HA, sweating, hypertrichosis (abnormal hair growth).
Associated with reflex sympathetic stimulation and sodium and fluid retention resulting in tachycardia, palpations, angina, and edema.
What must minoxidil be used with to avoid reflex sympathetic stimulation and sodium/fluid retention?
Loop diuretics and B-blocker
A person has abnormal hair growth and on meds for severe HTN. What med?
Minoxidil