Hypertensive drugs Flashcards
What is the mechanism of action for angiotensin-converting enzyme (ACE) inhibitors?
- ACE inhibitors act by blocking the effect of ACE.
- ACE is important in the conversion of Angiotensin I to II.
- Thus blocking it causes a reduction in circulating angiotensin II.
Reduction of angiotensin II has numerous effects:
- Reduced aldosterone secretion - involved in volume regulation via sodium and potassium excretion.
- Reduced ADH secretion - anti-diuretic hormone (ADH) acts on the kidneys to increase water reabsorption (independent of sodium).
- Reduced arterial vasoconstriction
- Reduced sympathetic activity
A dry cough is the most common adverse effect of which drug class?
Angiotensin-converting enzyme (ACE) inhibitors
Why does Angiotensin-converting enzyme (ACE) inhibitors commonly cause a dry cough?
A dry cough is a common side effect of ACE inhibitors.
ACE inhibitors cause the break down of bradykinin and thus there is an increase in bradykinin within the lungs
Name a few adverse effects of angiotensin coverting enzyme inhibitors (ACE inhibitors)
- Dry cough
- Headache
- Postural hypotension
- Rashes
- Angio-oedema
- Strongly teratogenic
What is the mechanism of action for Dihydropyridine calcium channel blockers (CCB)?
Dihydropyridine CCBs block the action of voltage-gated L-type calcium channels, which are found in vascular and cardiac tissue.
Within vascular smooth muscle, L-type channels permit the entry of calcium ions leading to contraction and subsequent vasoconstriction.
Dihydropyridine CCBs inhibit this influx of calcium ions and induce vasodilatation, which reduces the peripheral vascular resistance.
Name the two main types of Calcium channel blockers (CCBs)?
Dihydropyridine: predominantly anti-hypertensive effects.
Non-dihydropyridine: predominantly anti-arrhythmic effects.
Dihydropyridine CCBs block the action of which calcium channel?
Voltage-gated L-type calcium channels
Name some of the adverse effects of calcium channel blockers (CCB)?
- Headache
- Flushing
- Dizziness
- Peripheral oedema
- Reduced cardiac contractility
- Constipation
Bendroflumethiazide is a part of which drug class?
Thiazide diuretics
Nifedipine is a part of which drug class?
Calcium channel blockers (CCBs)
Lisinopril is a part of which drug class?
Angiotensin-converting enzyme (ACE) inhibitors
Ramipril is a part of which drug class?
Angiotensin-converting enzyme (ACE) inhibitors
What is the mechanism of action of Thiazide-like diuretic?
Thiazide diuretics act on the distal convoluted tubule (DCT) of the nephron where it inhibits the Na+/Cl- co-transporter. This prevents sodium and chloride entering the tubule cells and, therefore, water cannot follow.
This mechanism has an initial hypotensive effect; however, this is mostly abolished by the renin-angiotensin system (RAS).
Instead, thiazide diuretics long-term antihypertensive effects are due to vasodilation of peripheral vasculature through a mechanism that is poorly understood.
Thiazide diuretics act on which part of the nephron?
Distal convoluted tubule (DCT)
Thiazide like diuretics act on which receptor in the nephrons?
Thiazide diuretics act to inhibit the Na+/Cl- co-transporter on the distal convoluted tubule (DCT) of the nephron
Name some of the adverse effects of Thiazide like diuretics
- Gout
- Impotence
- Hyperuricaemia (precipitating gout)
- Hypercalcaemia
- Hypokalaemia
- Hyponatraemia
- Hyperlipidaemia
- Urinary frequency
Doxazosin is an example of what drug class?
Alpha-1 blockers
What is the mechanism of action of alpha 1 blockers?
Act to blockade alpha-1 adrenoreceptors
Alpha-1 adrenoreceptors are found in most sympathetic tissues including vascular smooth muscle and have excitatory effects. Stimulation results in vasoconstriction.
Consequently, blockade of alpha-adrenoreceptors causes:
- Reduced arteriolar tone - lowering peripheral vascular resistance.
- Venous dilation - reducing venous return and cardiac output.
Name some of the adverse effects of alpha 1 blockers?
- Postural hypotension
- Headaches
- Dizziness
- Nausea
- Rhinitis
- Urinary frequency
Propanolol is a part of which drug class?
Beta blockers
Atenolol is a part of which drug class?
Beta blockers
beta-1 receptors are found predominantly where?
In the heart
beta-2 receptors are found predominantly where?
Lungs
The antihypertensive effect of beta blockers are mediated primarily by blockade of which beta adrenoreceptors?
Blockade of beta-1 adrenoreceptors.
What is the definition of inotropic?
The strength of the contraction of the muscle
What is the definition of chronotropic?
Changes in heart rate
What is the mechanism of action of beta blockers
Beta-blockers act to reduce sympathetic activity.
The antihypertensive effect is mediated primarily by blockade of beta-1 adrenoreceptors. As such, they reduce the effect of the sympathetic nervous system on the heart. They, therefore, have both negative inotropic (reduce strength of contractions) and negative chronotropic (reduce heart rate)
Beta-blockers cause a reduction in blood pressure through a number of mechanisms:
-
Reduced cardiac output - through negative inotropic and negative chronotropic effects
- Negative Inotropic i.e. reduces the strength of contracts by the myocardium
- Negative chronotropic i.e. reduces the heart rate
- Reduced renin release by blockage of the sympathetic triggered release.
- Vasodilation due to blockade of beta-2 receptors in vascular smooth muscle (though the effect is thought to be minimal)
Name some of the adverse effects of beta blockers
- Postural hypotension
- Cold peripheries
- Headache
- Dizziness
- Insomnia, sleep disturbance
- Bradycardia
- AV nodal block (heart block)
- Bronchoconstriction (nonselective beta-blockers, a particular consideration in asthma and COPD)
- Hypoglycaemia (nonselective beta-blockers)
- Erectile dysfunction
