Pharmacology of Hypertension Flashcards
What are the 5 major cardiovascular risk factors?
Hypertension Hypercholsterolaemia Family history Diabetes Smoking
What is the Q-risk?
Calculator that predicts the likelihood of cardiovascular event
Why is it difficult to get people to take hypertension medication?
No immediate effects
It will improve your health status in the future e.g. 5-10 years time
But it may give you side effects on the day
Difficult to see the benefits of the drug
When do you begin hypertension medication?
Stage 1 hypertension: evidence of end organ damage, 10 year risk > 10% or have a cardiovascular disease
Stage 2 hypertension
How do you define stage 1 hypertension?
Systolic between 130-150
How do you define stage 2 hypertension?
Systolic over 150
What do NICE guidelines suggest for hypertension if you are Black or over 55?
Calcium Channel Blockers
Why are you not given ACEi if you are black or over 55?
Less likely to be hypertension where renin is significant
What is the relationship between plasma clearance and elimination half life?
As plasma clearance (ml/min/kg) decreases elimination half life increases
Time to peak plasma levels increase
Conc. of drugs with a long half life remains fairly stable
What is the mechanism of action of calcium channel blockers?
Prevents entry of calcium into smooth muscle of arteries, prevent contraction, causing vasodilation
What is clearance?
Clearance is the measure of the ability of the body to eliminate a drug. Clearance by means of various organs of elimination is additive. Elimination of drug may occur as a result of processes that occur in the liver, kidney, and other organs.
What is elimination half-life?
Elimination half-life is the length of time required for the concentration of a particular drug to decrease to half of its starting dose in the body.
What is the time to peak plasma levels?
Time to peak concentration is the time required for a drug to reach peak concentration in plasma. The faster the absorption rate, the lower is the time to peak plasma concentration.
What are the differences between amlodipine and felodipine?
Amlodipine has a much longer half life : never a moment when you do not have the drug in your system - accumulates
Dosed accordingly
How do ACEi work?
Inhibits angiotensin converting enzyme mainly in the lung
Prevents the conversion of angiotensin I –> 2 (potent vasoconstrictor)
Reduces aldosterone production - decreasing sodium reabsorption
What is a common side effect of ACEi?
Cough
What medication is given if someone develops a cough whilst taking ACEi?
ARBs
Angiotensin receptor blockers
Why do ACEi cause a cough?
ACE also breaks bradykinin
Stopping the enzyme increased bradykinin concentration causing a cough
Why does ARB not cause a cough?
You limit angiotensin directly and the enzyme is left to work - still breaks down bradykinin
Why do ACEi impact renal function?
To perfuse glomerulus, afferent arteriole must be open and efferent arteriole needs to be smaller to generate pressure
Angiotensin II keeps the efferent arteriole slightly closed
ACEi causes efferent arteriole to relax - reduced glomerular perfusion
Why do ACEi impact serum potassium?
Less aldosterone causes potassium retention
The job of aldosterone is to retain sodium at the expense of potassium
Spirolactone stops aldosterone binding its receptor has the same effect
What is the mechanism of action of indapamide?
Block sodium/chloride transporter in the distal tubule
Enables the reabsorption of any remaining sodium
Increases water reabsorption in the distal tubule
Increased urine output
Decreased cardiac output
What happens after you take thiazide diuretics for a while?
After a while a mechanism adapts to overcome the reduction in cardiac output
Cardiac output goes back to normal
So in reality they work by decreasing total peripheral resistance
Why do diuretics increase serum potassium?
More sodium delivered to the distal tubule
Reabsorbs sodium at the expense of potassium
