L17. Drugs Influencing the CVS Flashcards
What is the clinical definition of hypertension?
Blood pressure > 140/90 mmHg
Hypertension is a risk factor for…
Stroke MI, Ischaemic heart disease, chronic heart failure Aortic aneurysm, retinal haemorrhage Renal Failure Death
What are the risk factors for developing hypertension?
A multifactorial disease:
Smoking, diet, weight, stress, family Hx
What is the aim for hypertension therapies?
Reduce the blood pressure below 140/85
Or below 130/80 for diabetic for obese patients
Mainly achieved by reducing the risk factors
For Homeostatic control of blood pressure: Regulated variable is \_\_\_\_ Sensors \_\_\_\_ Controlled variables \_\_\_\_\_\_ Effectors \_\_\_\_\_ Effector Signals \_\_\_\_\_\_\_
Regulated variable is __Blood Pressure__
Sensors __Baroreceptors and Osmoreceptors__
Controlled variables __HR and SV (CO) and TPR____
Effectors __Blood vessels, Heart and Kidney___
Effector Signals __Neuronal and Hormonal__
Which system (Para or symp) takes precedence in controlling BP?
Sympathetic is the major regulator for changing blood pressure (parasympathetic is for rest situations)
What receptors to noradrenaline and adrenaline act on to control blood pressure?
alpha 1 adrenoreceptors in the blood vessels
beta 1 adrenoreceptors in the heart and in the kidneys
What are the main results of adrenaline acting on these receptors in blood y
pressure regulation?
Vasoconstriction
Increased HR
Increased Contractility
Increased Blood Volume
Describe the Renin-Angiotensin System
Noradrenaline binding to B1 receptors in the kidney
Stimulates secretion of renin by the kidney
Converts angiotensinogen into angiotensin I
ACE converts angiotensin I into angiotensin II
Angiotensin II
What are the main actions of Angiontensin II?
Acts on AT1 receptors: Vasoconstriction of blood vessels Acts on AT1 receptors: Release of aldosterone leading to salt and water retention Cell growth (hypertrophy of the heart) Positive feedback to sympathetic nervous system (increase noradrenaline)
Why would we use Angiotensin Converting Enzyme Inhibitors (ACE inhibitors) in hypertension?
They prevent the conversion of AngI to AngII: reducing vascular tone, reducing aldosterone production (reduces water retention, reduces SV) and reduces cardiac hypertrophy
What is another mechanism of ACE inhibitors (involving bradykinin)?
ACE works like Kininase II: breaks down bradykinin
ACE inhibitors prevent bradykinin breakdown allowing it to have longer potent vasodilatory effects
What are the adverse effects of ACE inhibitors?
Dose Dependent: First dose hypotension dry cough loss of taste hyperkalaemia (often given in combination with diuretics) Acute renal failure Itching, rash, angio-oedema Foetal malformations
What are some contraindicators of ACE inhibitors?
Pregnancy
Bilateral renal stenosis
Angio-neurotic oedema
What are some examples of ACE inhibitors?
The -PRILS Captopril Perindopril Enalapril Ramipril
What are the antiotensin receptor antagonists?
The SARTANS
Losartan
Candesartan
What happens with you block the AT receptors?
AT1 and AT2 Reduce vasoconstriction Reduce aldosterone formation Reduce cardiac hypertrophy Reduce sympathetic activity (inhibits the positive feedback)
What is the major difference between AT antagonists and ACE inhibitors (that it thought to make them safer)?
AT antagonists do not have an effect on bradykinin
What are the adverse effects of AT antagonists?
Hyperkalaemia
Headache
Dizziness
What are the contraindications for AT antagonists?
Contraindicators are the same for the ACE inhibitors:
Pregnancy
Bilateral renal stenosis
Angio-neurotic oedema
What are the b1 adrenoreceptor antagonists?
The -OLOLS Propanolol Timolol (nonselective) atenolol metoprolol (b1 selective) pindolol (partial agonist for b1 and b2)
What is the aim of using B1 adrenoreceptor antagonists in hypertension?
Reduce the Cardiac Output and reduce renin release (decreases blood volume) by preventing sympathetic innervation
How to the B blockers vary within the class? [3]
- Vary with selectivity (for receptors)
- With intrinsic sympathomimetic activity (eg. partial agonist activity)
- Vary with lipid solubility (eg. ability to cross the blood brain barrier)
What are the adverse effects of b adrenergic receptor antagonists?
Cold extremities: occurs acutely when CO is dropped by the drug, a reflex alpha 1 constriction occurs
Fatigue: puts a limit on the sympathetic nervous system to increase HR and blood vessel supply
Dreams and insomnia (CNS lipid solubility)
Bronchoconstriction (B2 adrenoreceptor blockage)
What are some contraindications for b1 adrenergic receptor antagonists?
Asthma
Diabetes
AV conduction block
Must take care with heart failure and metabolic syndrome
What are the Calcium Channel Blockers?
Vermpamil
Diltiazem
Dihydropyridines: felodipine and nifeipine
What is the mechanism of action of the Calcium channel blockers in hypertension?
Inhibit voltage gated L-type Calcium channels in the myocardium and the vasculature.
= reduced cardiac and vascular contractility
= Reduced vascular resistance
What are the 2 types of calcium channel blockers?
- reduce cardiac and vascular contractility
2. Reduce vascular resistance
What are the adverse effects of calcium channel blockers?
Oedema, flushing, headache
Bradycardia (for reduced cardiac contractility)
Reflex tachycardia (for reduced vascular resistance)
What is the mechanism of action of thiazide diuretics in terms of hypertension?
Inhibit NaCl co-transporter in the distal convoluted tubule of the kidneys leading to decreased reabsorption: increases the Na and water excretion form the kidney
Also has a loss of K from the collecting duct
= lowers blood volume
What is an example of a thiazide diuretic used in hypertension?
Hydrochlorothiazide
What is an adverse effect of the thiazide diauretics?
Hypokalaemia: Loss of K leading to gout, hyperglycaemia and allergic reactions
What are some other drugs used in hypertension (when the main ones don’t work)?
Alpha 1 adrenoreceptor antagonists
Vasodilators
alpha 2 antagonists (CNS)
New renin inhibtors
What are the main drugs used to combat hypertension?
ABCD Angiotensin System Inhibitors B-adrenoreceptor antagonists Calcium channel blockers Diuretics
Why do we have so many anti-hypertensive drugs?
Because it is a multifactorial disease with both neural and hormonal control
Multiple target organs, signals and proteins
Often use a combination of drugs