Antihypertensives Flashcards
What are the first line antihypertensive drugs?
- Angiotensin inhibitors (ACE-is) and (ARBs)
- Beta blockers
- Calcium Channel Blockers
- Diuretics
What are some common ACE-Is?
- Lisinopril (Long half-life)
- Enalapril (Long half-life)
- Captopril (Short half-life)
All drugs -pril
Mechanism of ACE-Is
- Blocks conversion of Ang1 to Ang2
- Lesser vasoconstriction and aldosterone levels
- Lower aldosterone levels will lead to lower Na+/H2O retention thereby lowering BP
- Decrease peripheral resistance and reduce BP
- Blocks inactivation of Bradykinin
-Bradykinin levels increase - Forms NO and PG which causes vasodilation
How are ACE-Is excreted
Renal excretion, decreased dose in renal insufficiency
Side effects of ACE-Is
- Severe Hypotension (All hypertensive drugs can cause Hypotension)
- No reflex sympathetic activation, ACE-Is reset pressure sensor sensitivity, blocking baroreceptor reflex
- Acute renal failure
- Hyperkalemia, increase K+ retention in bloodstream
- Angioedema/Dry cough induced by bradykinin and Substance P
- Angioedema (Allergic run, lip tongue swelling)
Which group is ACE-Is contraindicated in?
Pregnant woman
Clinical indications for ACE-Is
- Hypertension
- Cardiac failure (Following MI, together with aspirin, beta-blocker and statins)
- Renal insufficiency (Decrease efferent arteriole vasoconstriction, decrease glomerular pressure, decrease proteinuria and increases function)
Name some common Ang2 Type 1 (AT1) receptor blockers
- Losartan
- Valsartan
- Candesartan
all dugs -sartan
(Medications of choice if ACE-Is cannot be tolerated)
Why doesn’t AT1 cause dry cough
Angiotensin II type I inhibitors don’t increase the bradykinin levels, thus no bradykinin effect systemically
What are some common beta blockers?
Non selective:
1. Propanolol
2. Pindolol
3. Carvedilol
Cardioselective:
1. Atenolol
2. Bisoprolol
3. Metoprolol XL
Mixed (3rd Generation):
1. Nebivolol (Beta 1 selective in lower dose, non-selective in higher dose)
Define cardioselective
Selective inhibits Beta 1 adrenoceptors (works on the heart)
Nebivolol mechanism
Decreases vascular resistance by stimualting β-3 receptors and activating NO synthase in the vasculature
Release of NO for vasodilatory effects
Mechanism of beta blockers in hypertension
- Diminish phase 4 depolarisation
- Depress automaticity
- Prolong AV conduction
- Decrease Heart rate and contractility
How does beta-1 adrenoceptor antagonist reduce BP
- Decreases contractility of calcium channels, leading to decreased Calcium influx and Ca-calmodulin complex formation
- Inactivation of MLCK and hence unable to convert Myosin-LC to Myosin-LC# which deactivates it and reduce contraction
- Relaxation of cardiac muscles and reduce contractility
Why are non-selective beta blockers (Propranolol) contraindicated in asthmatic patients
- Blocking beta 2 receptors on smooth muscles prevents the relaxation of the muscles (phosphorylation of MLCK and deactivate it)
- Asthma very easily provokes this problem
- Adrenaline originally provides a base level of broncho relaxation
- Without which due to beta blockers, there will no longer be a baseline level of dilation for smooth muscles, increasing chances of an asthma attack
Adverse effects of Beta Blockers
- Bradycardia
- CNS: Mild sedation, vivid dreams
- Asthma
- Withdrawal symptoms: Upregulation or super sensitivity of adrenoceptors
- Contraindicated in diabetic patients
Why are beta blockers dangerous for diabetic patients?
Masking of Hypoglycemia Symptoms:
Symptoms of hypoglycemia, such as tachycardia and palpitations, are partly mediated by the release of adrenaline (epinephrine), which activates beta receptors.
Beta blockers block the effects of adrenaline, which can prevent the typical symptoms of hypoglycemia, leading to delayed recognition and treatment of low blood sugar levels.
What are some typical calcium channel blockers?
DHP CCB
1. Nifedipine
2. Felodipine
Non DHP CCB
1. Verapamil
2. Diltiazem
What’s the difference between DHP and non DHP CCB?
DHP predominantly work on smooth muscle cells whereas non-DHP acts on cardiac cells
Therefore as a cardiac depressant: Verapamil»_space; Diltiazem»_space; Nifedipine
However, as a Vasodilator: Nifedipine»_space; Diltiazem»_space; Verapamil
Mechanism of Nifedipine (DHP)
- Preferentially targets L type calcium channels in smooth muscle cells
- Binds to and blocks L type Calcium channels
- Decreased frequency of Ca2+ channel opening in response to cell membrane depolarisation → decreased transmembrane Ca2+ current
- Vascular smooth muscles relax leading to vasodilation → decrease PVR → decreased afterload → decreased BP
- Ca2+ binds to Calmodulin forming Calcium-calmodulin complex, activates Cam-kinase
- Cam-kinase converts myosin light chain kinase to phosphorylated myosin light chain kinase
Mechanism of non-DHP (Verapamil)
- Blocks Ca2+ channes
- Decrease intracellular Ca2+
- Decrease SA/AV node conduction
- Decrease supraventricular, re-entry tachycardia
Adverse effects of DHP CCB
- Headache
- Peripheral edema
- Flushing
- Reflex tachycardia
- Gingival hyperplasia
Adverse effects of non-DHP CCB
- Cardiac depression: Bradycardia, AV block, Heart failure
Due to decrease HR and contractility, inhibition of signal transaction from atrium to ventricle thus cannot be used to treat heart failure
Route of administration of CCB
- Oral high first pass effect
- Verapamil and Nifedipine also IV
- More selective for cardiac muscle (Verapamil > Diltiazem)