Drugs for Hypertension - Part 3 & 4 Flashcards
Describe Calcium Channel Blockers (CCBs) & when they are useful
- Excellent first line single therapy in uncomplicated hypertension
- Low incidence of side effects (but expensive)
- Neutral metabolic profile (no effect on cholesterol and glucose)
- Useful when beta-blockers are contraindicated
- not contraindicated in asthma, COPD, or diabetes
What are two classes that block L-type calcium channels?
– Vascular Acting (dihydropyridines): amlodipine, NIFEDIPINE
* greater affinity for vascular calcium channels
– Cardiac (non-dihydropyridines): VERAPAMIL, DILITIAZEM
* blocks calcium channels primarily in cardiac tissue
Describe Vascular Acting(dihydropyridines) which Block L-type calcium channels (Calcium Channel Blockers - CCBs)
AMLODIPINE, NIFEDIPINE
* greater affinity for vascular calcium channels (acting primarily through arterial system)
* relaxes blood vessels (arteries)
** reduce TPR WITHOUT apparent direct cardiac actions
When are Vascular Acting(dihydropyridines) which Block L-type calcium channels (Calcium Channel Blockers - CCBs) useful/used for?
– Useful for angina and hypertension treatments (chronic HTN)
– Used for hypertensive crisis
– Long acting medications are used for hypertension
– Also used to treat pulmonary hypertension
– NIFEDIPINE is safe to use for blood pressure lowering in pregnancy – diuretics may block nifedipine effects on BP
Describe Cardiac (non-dihydropyridines) which Block L-type calcium channels (Calcium Channel Blockers - CCBs)
VERAPAMIL, DILTIAZEM
– Used to treat hypertension when there is a concern about heart rate regulation in atrial fibrillation or in patients with angina
Verapamil:
- blocks calcium channels mainly in cardiac tissue
- Should not be combined with a beta-adrenergic receptor blocker because both drugs block AV node (therefore, decrease HR –> decrease CO even more than it is)
- Contraindicated in heart failure
(a Cardiac (non-dihydropyridines) which Block L-type calcium channels (Calcium Channel Blockers - CCBs)
Diltiazem:
- both vascular and cardiac effects
- Used to treat angina and hypertension
What are Calcium Channel Blockers Adverse Effects?
- Adverse effects related to vasodilation: (get too much vasodilation & decrease BP)
- especially:
- increased mortality post-MI with short acting preparations of nifedipine
- never decrease BP rapidly, only 20mmHg at a time
** Combination of beta-blockers with CCBs leads to hypotension - Amlodipine causes carries risk of edema
- Combination with ACEi avoids edema
- since verapamil reduces cardiac contractility it *can’t be used in heart failure
- published concerns about increased risk of cancer and GI bleeding appear unsubstantiated in larger studies
(quite safe to treat HTN)
What are Common Side effects of Calcium Channel Blockers?
- Constipation
- Vertigo
- Headache
- Fatigue
- Hypotension
What are Metoprolol & Carvedilol?
B-Adrenergic Receptor Blockers
Describe B-Adrenergic Receptor Blockers
Metoprolol, Carvedilol
- many many B-blockers but all ↓ blood pressure.
- mechanism of BP reduction not really known.
– obvious to think - decreased CO
— but CO may return to normal over the long-term
Describe B-Adrenergic Receptor Blockers
Carvedilol
- blocks B- AND a-adrenergic receptors (non-selective)
- a-adrenergic receptor blockade helps to relax (dilate) arteries
– the heart does not have to work as hard to eject blood
— decreases afterload - B-adrenergic receptor blockade slows the heart and decreases force of contraction (↓ BP)
Describe B-Adrenergic Receptor Blockers
Metoprolol
- similar benefits to carvedilol
- selectively blocks B1-adrenergic receptors (↓ BP)
How effective are B-Adrenergic Receptor Blockers?
- effective (?) treatment but now controversy - not metabolically neutral
– increased TG, reduced HDLs
(may be why they’re)— increased incidence of type 2 diabetes
– lower blood pressure but no decrease in cardiovascular mortality (or overall mortality)?
(ACEi lower CV mortality, so are better, BB have no effect on CV mortality)
When are B-Adrenergic Receptor Blockers not effective/effective?
Not recommended as single therapy in uncomplicated hypertension
- effective in other situations (and therefore used)
- preventing 2nd myocardial infarction (major)
- improvement of heartf ailure(major)
What are side effects of B-Adrenergic Receptor Blockers?
- Hypotension (may potentially cause large drops in BP)
- Bradycardia (blocks B1-adrenergic receptors on the heart - normally not a problem to have a low HR)
- Fatigue (CNS effect)
- Insomnia (CNS effect)
- Sexual Dysfunction (decreased libido, may cause impotence - compliance issues?)
– decrease compliance with taking BB (don’t want to just stop taking b/c will get rebound HTN & will be higher than before taking, therefore take them off slowly)
When should you avoid/take B-Adrenergic Receptor Blockers?
- avoid sudden withdrawal
- good to block reflex activation of the heart by the SNS
- avoid where β-adrenergic receptor activity needed:
- asthma, COPD, peripheral vascular disease, insulin dependent diabetes, physically active (?)
- good if certain other diseases present (treats both):
- glaucoma, certain arrhythmia, myocardial infarction, angina
What is an example of an alpha1-Adrenergic Receptor Antagonist? Describe it
Prazosin
- not effective as a single agent for chronic BP lowering
- vasodilates arteries and veins
What are the problems with alpha1-Adrenergic Receptor Antagonist in particular Prazosin?
- first dose effect: initial large ↓ BP
- postural hypotension
– Patients should not stand up too quickly due to poor baroreflex - fluid retention with long-term treatment due to Na+ retention
– give with diuretic (to try prevent electrolyte imbalances & fluid retension)
What is an example of an alpha2-Adrenergic Receptor Agonist? Describe it
Clonidine
- acts on central vasomotor centres
- decreases SNA from the CNS
- net effect is to reduce peripheral vascular resistance - autonomic system remains intact
- given as two unequal doses
*– high dose at night: sedation (b/c makes you feel tired & than lower dose during day - b/c acting on CNS)
- typically used when patient is resistant to the use of other BP lowering medications (add on)
What are the problems with alpha2-Adrenergic Receptor Agonist in particular Clonidine?
- rebound hypertension upon rapid cessation of drug (risk of not taking their medication)
- dry mouth, sedation and hypotension potential adverse effects
- not recommended to be used in pregnancy
What are Vasodilators NOT used for?
Not used for chronic blood pressure lowering (more for hospital setting - therefore less commonly used)
What are 2 examples of Vasodilators?
- Hydralazine
- Sodium nitroprusside
Describe Hydralazine
a Vasodilator
- relaxes vascular smooth muscle cells of resistance arterioles
- use in combination with a -blocker and diuretic
– stimulates SNA so may increase heart rate
– increases plasma renin so results in fluid retention (why a diuretic is also used)
*- used in pregnancy (gestational hypertension)
- safe for mother and infant and effective
What are the problems with Hydralazine (a vasodilator)?
- risk of lupus-like syndrome with long-term treatment (inflammatory disease)
- headache, hypotension, tachycardia, angina
- may potentiate anti-hypertensive effects of ACEi, CCBs and diuretics (good or bad thing - could lower BP too much)
Describe Sodium nitroprusside
a Vasodilator
- both venous and arteriolar dilator
- infused intravenously
– breaks down to produce nitric oxide (NO) (a potent vasodilating molecule)
- used for acute hypertensive crisis (emergency)
What are problems with Sodium nitroprusside (vasodilator)?
- potential for cyanide toxicity (b/c highly reactive NO molecule so potential for cyanide toxicity)
- should not use in pregnancy
- risk of hypotension, low heart rate
- do not use in patients with kidney disease
Drug therapy for specific disease mechanisms of hypertension
What is used for Volume overload?
– Thiazide; loop diuretic; aldosterone antagonist
(underline edema)
Drug therapy for specific disease mechanisms of hypertension
What is used for Sympathetic overactivity?
– B-blocker (use to counteract reflex tachycardia from vasodilators or in heart failure)
Drug therapy for specific disease mechanisms of hypertension
What is used for Increased vascular resistance?
– ACE inhibitor or ARB (use in heart failure)
Drug therapy for specific disease mechanisms of hypertension
What is used for Smooth-muscle contraction?
– Dihydropyridine CCBs; B-blocker; hydralazine (vasodilator)
How often should patients with hypertension be seen?
If they have Stable, well-controlled hypertension?
Recheck at 6- to 12-month intervals
How often should patients with hypertension be seen?
If their Blood pressure 140/90 to 159/99mmHg?
Recheck at 2 months intervals (stage 1)