Anti Hypertensive Drugs Flashcards
Hydrochlorothiazide (HCTZ) as an anti-hypertensive?
- ->Diuretic (increases secretion of H2O- reduce blood volume and drop BP)
- Inhibits Na+/ Cl- Co transport
- Increases secretion of Na+, Cl-, K+ and H+
- Increase Ca2+ reabsorption
After 1 month of thiazide diuretic use for hypertension, there is a decrease in TPR and an increase in CO.
Adverse Effect: Compensatory increase in renin which may prevent the drop in BP, as well as hypercalcemia, hypovolemia, hypokalemia, alkalosis, hyperuricemia and hyperglycemia.
–>ACE inhibitors/ ARB work well to decrease the increased renin effects.
What is the major drawback of Thiazide diuretics in treating hypertension?
- Thiazides decrease CO by increasing the excretion of water in the urine. This causes a reflex increase in renin due to the drop of blood volume.
- This can be controlled with the combination of an ACE inhibitor and ARB to block these compensatory effects of renin.
Atenolol and Metaprolol for the treatment of Hypertension?
–>Beta 1 Antagonists
-Decrease CO and then TPR (block renin release)
(decrease RAAS activation!)
- Very effective when angina is present!
- Reduces angina, hypertension and tachycardia.
Adverse effects:
-Withdrawal syndrome if stopped suddenly.
SAVE LIVES!!!
Amlodipine, Nifedipine- DHPs
Diltiazem and Verapamil to treat hypertension?
- Blocks Ca2+ influx by inhibiting L type calcium channels.
- ->Vasodilation
- DHP’s may cause reflex tachycardia
- Useful with Beta 1 blocker, ACE inhibitor or ARB to decrease sympathetic compensation of the RAAS (less problematic with CCB’s)
Adverse effects: Constipation, flushing and headache.
Hydralazine as a hypertensive?
Nitro-vasodilator:
- Weak anti-hypertensive agent when used alone because of the compensatory increase in CO as a result of reflex veno-constriction and the expansion of blood volume due to Na+/ H2O increase.
- Use with a Beta blocker or diuretic to block these compensatory mechanisms.
Enalapril*
-Captopril, Lisinoprol, Ramipril and Perindopril for the treatment of hypertension:
- ACE inhibitors (prevent the conversion of ANG I into ANG II)
- Decrease levels of ANG II and increases BK
- Effectively lower BP by lowering blood volume
Drawbacks:
- Reduces secretions (dry cough)
- Blocks AT2 receptors (clearance receptors)
Losartan*
-Valsartan and Irbesartan as anti-hypertensives?
-Angiotensin II Receptor Blockers (ARBS)
- > No effect on levels of BK unlike ACE inhibitors
- > No effect on AT2 receptors unlike ACE inhibitors
-Blocks AT1 receptors causing vasoconstriction, as well as AT1 receptors activating the adrenal cortex which induce aldosterone secretion (leads to vasodilation and decreased blood volume)
Drawback:
- Once AT1 blockers are removed, RAAS spikes levels of renin and ANG II, leading to Rebound Hypertension.
- More expensive
Why are diuretics to treat hypertension contraindicated in patients with hypovolemia?
- Increased more and more water excretion
- May precipitate renal failure in patients with renal artery stenosis (abnormal renal artery narrowing)
Nitrovasodilators to treat hypertension?
- SNP
- Minoxidil
- Hydralazine
- Not useful alone- increase HR reflexively
- In long term use, effective as a third line drug.
Clonidine to treat hypertension?
Alpha 2 agonist
-Used short term to decrease sympathetic discharge.
Several Adverse Effects (dry mouth, sedation and CNS effects)
Aliskiren to treat Hypertension?
- Direct Renin Inhibitor (DRI)
- Supresses renin release (drops blood volume and BP)
-No long term data (claimed to be superior to ARBs and ACE inhibitors- not proven true)
Expensive!
MAIN activity of Beta1 Blockers:
-Decreases renin binding. (decrease RAAS)
MAIN activity of ACE-Inhibitors?
- Blocks the conversion of ANG I to ANG II.
- Increases BK
- Increases cough!
MAIN activity of ARBs:
Blocks ANGII binding AT1 receptors (blocks vasoconstriction) and causes vasodilation.
-No effect on BK
MAIN activity of DRIs:
-Blocks renin secretion (decreases ANG I levels)
No effect on BK levels
