Anti-Hypertensive drugs Flashcards
Classification of these drugs?
- Adrenolytic (Reduce the output of hormones from the adrenal glands)
a. Alpha 1 blockers (Prazosin and doxazosin)
b. Beta blockers (“selective” - Metoprolol, atenolol and nebivolol) and (“non-selective” - Propranolol).
c. Non-selective alpha 1-beta blockers (labetalol and carvedilol).
d. Alpha 2 agonists (Clonidine and methyl-dopa).
- Drugs affecting RAAS
a. Angiotensin converting enzyme (ACE) inhibitors (Captopril, enalapril and lisinopril)
b. Angiotensin II receptor antagonists (Losartan)
c. Renin inhibitors (Aliskiren) - Calcium Channel Blockers
a. Diphenylalkylamines (Verapamil)
b. Benzothiazipines (Diltiazem)
c. Dihydropyridines (Nifedipine, amlodipine, felodipine and isradipine). - Antihypertensive Diuretics (Thiazides, loop diuretics)
- Antihypertensive vasodilators (Hydralazine and minoxidil)
Explain “Thiazide diuretics”.
They function to increase sodium and water excretion for initial reduction in blood pressure. The effects of this are:
- Reduced cardiac output
- Reduced renal blood flow (Reduced systemic circulation volume of the blood).
- Decreased extracellular fluid volume
Long term use of the thiazides ( Hydrochlorothiazide and chlorthalidone) achieves a normal Bp. However hypotensive effects may arise, which may cause a reduction of “peripheral vascular resistance” (increased blood flow to the tissues and increased venous return to the heart) - reduced volume of blood.
Adverse effects of thiazides are Hypokalaemia, hyperuricemia and hyperglycaemia.
Explain “Loop diuretics”.
They function to block sodium and chloride reabsorption, hence increase their excretion. Remember sodium induces water content in the blood which increases volume and overall Bp. Loop diuretics cause reduced PVR (vasodilatory effect) which as a result increases the renal blood flow.
Like thiazides loop diuretics cause hypokalaemia, used in patients with heart failure, oedema and reduced response to the thiazide diuretics. Examples include “Furosemide” and “torsemide”.
Explain the “beta blocker” adrenolytic hypertensive drugs.
They function to reduce the cardiac output and also to reduce the sympathetic outflow (reduced renin, angiotensin 2 and aldosterone secretion). Metoprolol (IV), atenolol and nebivolol are examples of “Selective beta blockers”, should be used with caution in patients with asthma. Propranolol is a non-selective beta blocker, contra indicated in asthma patients due to blockage of “Beta 2 mediated broncho dilation”.
Benefits of beta blockers are in hypertensive patients with concomitant disorders such as a previous MI, supraventricular tachyarryhthmias and ischemic heart disease.
Adverse effects of beta blockers as anti-hypertensives?
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- Hypotension
- Bradycardia
- Fatigue
- Insomnia
- Sexual dysfunction
Abrupt withdrawal of these drugs may also lead to severe hypertension, Myocardial infarction and even death in some patients. So it is important to take time with the withdrawal process.
Explain ACE inhibitors.
These drugs (Captopril, enalapril and lisinopril) function to reduce peripheral vascular resistance, without increased cardiac output, heart rate and heart contractility. The block the ACE enzyme, preventing the formation of “angiotensin 2” (potent vasoconstrictor). Blocked AT2 production means reduced Aldosterone secretion (low sodium and water reabsorption).They also breakdown bradykinin (Nitric Oxide and prostacyclin activator) for vasodilatory effects.
ACE inhibitors are well orally absorbed, undergo hepatic metabolism into active metabolites. its therefore good for use in patients with hepatic dysfunction in order to reduce the breakdown of the drugs.
Therapeutic uses of “ACE inhibitors”?
- Slows progression of diabetic neuropathy.
- Reduces renal blood pressures by vasodilation of efferent arteriole.
- Excellent treatment for patients after myocardial infarction.
- Regression of left ventricular hypertrophy.
- Prevention of ventricular remodelling after myocardial infarction.
- Achievement of a sustained blood pressure after chronic use.
ACE inhibitor adverse effects?
(Does, having, severe, hypotension, ache, a lot?)
Dry cough, hypokalaemia, skin rash, hypotension, altered taste and angio-oedema.
Explain “angiotensin 2 receptor blockers”.
The drug “Lorsartan” functions to block AT1 receptors, preventing the binding of angiotensin 2. Similar pharmacological effects to the ACE inhibitors (bradykinin breakdown, reduced aldosterone). They are first line treatments for patients with chronic renal disease, diabetes and heart failure. They should not be used in pregnancy or in combination due to the risk of adverse effects from using the same mechanisms.
ARB’s side effects?
Angio oedema and dry cough but of a lower severity compared to ACE inhibitors.
Explain “Renin Inhibitors”.
The drug “Aliskiren” has early blockage of RAAS compared to ACE/ARB’S, as they block the production of angiotensin one from renin. Diarrhoea is adverse effect at high doses and can also lead to cough/angio oedema of lower severity. Metabolised by CYP3A4 isoenzyme.
Explain “Calcium channel blockers”.
Calcium channel blockers are useful in hypertensive patients with ischemic heart disease and diabetes. There are 3 groups of CCB’s, namely (Diphenylalkylamines, benzothiazipines and dihydropyridines). They function to block the L-type calcium channels to induce vasodilation of arterioles only and not veins.
Diphenylakylamine (Verapamil) = Cardiac/smooth muscle action. Used for treatment of angina and supraventricular tachy-arrhythmias.
Benzothiazipines (Diltiazem) cardiac and smooth muscle action with more favourable side effect profile compared to diphenylalkylamines.
Dihydropyridines: Greater affinity for vascular calcium channels, beneficial for hypertensive treatment.
Adverse effects of CCB’s?
“People, feel, dizziness, headaches and hypotension”
- Peripheral oedema
- Flushing (redness)
- Dizziness
- Headaches
- Hypotension
CCB therapeutic uses?
Initial therapy for hypertension and all CCB’s are useful for the treatment of angina.
Explain the Alpha 1 blockers?
They block alpha 1 receptors to reduce PVR and induce vasodilation in both arterioles and veins, with minimal changes to the cardiac output and renal blood flow. Only problems with these is that “postural hypotension” and “reflex tachycardia” may occur at treatment onset. Examples are “prosozin and doxazosin”
