Diuretics/HTN

Question 1

Describe the pharmacology of loop diuretics including their therapeutic use and ADRs

Answer 1

E.g. Furosemide
Act on Na/K/2Cl symporter
Inhibit sodium chloride, potassium reabsorption
Increased prostaglandin production
Therapeutic use - treat hypertension, oedema from heart failure
Effective in patients with impaired kidney function
ADRs - low sodium, potassium, magnesium, dehydration, gout, postural hypotension, ototoxicity, myalgia

Question 2

Describe the pharmacology of thiazides diuretics including their therapeutic use and ADRs

Answer 2

E.g. Benzothiadiazine
Act on Na/Cl symporter in DCT
Inhibit sodium and chloride reabsorption, increase calcium reabsorption
Therapeutic use - treat hypertension, oedema from heart failure, hypocalcaemia
ADRs - hyperglycaemia, lipidaemia, uricaemia, low sodium, potassium, magnesium, erectile dysfunction
Contraindicated in patients with hypotension, gout, renal failure, hypokalaemia, pregnancy

Question 3

Describe the pharmacology of carbonic anhydrase inhibitors

Answer 3

E.g. Acetazolamide, Dorzolamide

Works on PCT - excretion of sodium bicarbonate, chloride and water

Question 4

Describe the pharmacology of potassium sparing/aldosterone antagonist diuretics including their therapeutic use and ADRs

Answer 4

E.g. Amiloride, Spironolactone
Works on DCT, CD
Competitive antagonist with aldosterone, blocks ENaC
Inhibits sodium reabsorption and potassium and hydrogen ion secretion
Adjunctive therapy to maintain K+
ADRs - high K+ (when used alone) –> arrhythmias, androgenic cross reactivity –> painful gynaecomastia

Question 5

List some important drug interactions with diuretics

Answer 5

ACEi, aminoglycosides, digoxin, B-blockers, corticosteroids, carbamazepine

Question 6

List some of the functions of the kidney

Answer 6

Regulatory - fluid balance, acid/base balance, electrolyte balance
Excretory - waste products, drug elimination
Endocrine - RAAS, erythropoietin, prostaglandins
Metabolism - vitamin D, polypeptides (insulin, PTH)

Question 7

Describe the pharmacology of ACEi including their method of action and ADRs

Answer 7

E.g. Ramipril, Lisinopril
Decrease angiotensin 2 –> vasodilation, venodilation, decrease circulating aldosterone, increase bradykinin
ADRs - angiooedema (black population), renal failure, high potassium, dry cough

Question 8

Describe the pharmacology of ARBs including their method of action and ADRs

Answer 8

E.g. Losartan, Candesartan
Bind to AT1 receptor
Well tolerated
ADRs - renal failure, high potassium

Question 9

Describe the pharmacology of calcium channel blockers including their method of action and ADRs

Answer 9

E.g. Amlodipine, Verapamil
Bind to specific alpha subunit of L-type calcium channels –> vasodilates
ADRs - tachycardia, palpitations, flushing, headache, constipation, bradycardia, worsen heart failure

Question 10

What is a hypertensive emergency and what needs to be given?

Answer 10

220/120 mmHg

Give sodium nitroprusside

Question 11

Describe how to treat secondary hypertension from phaechromocytoma and primary hyperaldosteronism

Answer 11

Phaeochromocytoma - non selective a blockers then b blockers

Primary hyperaldosteronism - aldosterone antagonist or high dose amiloride

Question 12

Summarise the major principles underlying drug therapy in heart failure

Answer 12

Improve prognosis by RAS antagonism - ACEi, ARB, aldosterone antagonists, B blockers
Diuretics - loop +/- thiazides