Anithypertensive Drugs- Diuretics

Question 1

Thiazide and related diuretics?

Answer 1

• inhibit sodium reabsorption at the beginning of the distal consulates tubule
• Acts within 1-2 hours of oral administration and effects acts for 12-24 hours
• Give in the morning to avoid diuresis and night which can interfere with with sleep
• moderately potent
  -indication - lower doses reduce blood pressure with little biochemical balance. Higher doses are used for odema due to CHF. More effects on biochemical balance (potassium,sodium,uric acid and glucose/lipids) with little advantage on blood pressure - eg. Bendroflumethazide - used for mild or moderate HF or hypertension this is no longer first line)
  Chlortalidone - long duration of action and may be given on alternative days
• Indapamide — lowes bp with less effects on electrolyte imbalance and lesss agrivation on diabetes

Question 2

Contraindications for thiazides and related diuretics

Answer 2

• avoid in hypokalaemia, hyponatraemia, hypercalcaemia and addisons disease(low levels of sodium and high levels of potassium)

Question 3

Cautions and further info for thiazide and related diuretics

Answer 3

• hypokalaemia can occur with loop and thiazide diuretics
• risk of hypokalaemia greater with thiazides than with loop
• hypokalaemia is dangerous with patients with severe CV disease or patients on cardiac glycosides
• potassium sparring diuretics or potassium supplements can be used
• in hepatic failure, hypokalaemia can lead to encephalopathy- particularly in alcoholic cirrhosis

Question 4

Caution and further info for thiazide and related diuretics

Answer 4

Elderly are more susceptible to side effects of diuretics ( give lower initial doses)

Dose should be adjusted according to renal function

Diuretics should not be sued on a long term basis to treat gravitational oedema (which will usually respond o increased movement- raising legs and support stockings

• thiazide and related diuretics can exacerbate diabetes and gout - because they can cause hyperglycaemia + hyperuriciaemia)

Question 5

Thiazides and related diuretics - side effects, pregnancy and hepatic and renal impairment

Answer 5

• constipation, electrolyte imbalance, headaches,postural hypotension and skin reactions
• Pregnancy - thiazide and related diuretics should not be used to treat gestational hypertension
• they may cause neonatal thrombocytopenia, bone marrow suppression, jaundice, electrolyte imbalances
• hepatic impairment and renal impairment -
• use with caution nd avoid severe liver disease
• thiazides and related diuretics are ineffective if eGFR is less than 30 and so should be avoided

Question 6

Loop diuretics

Answer 6

Examples - Furosemide and bumetanide
- inhibit reabsorption from the ascending loop of hence (powerful diuretic)
- used in pulmonary oedema due to left ventricular failure and in CHF
- Stronger diuretics than thiazides and can be used for resistant odema
- longer diuretics can exacerbate diabetes (but hyperglycaemia is less likely than with thiazides) and gout
- furosemide and bumetanide act within 1 hour of oral admin and similar in activity
- diuresis is complete within 6 hours can be given twice a day without interfere ring with sleep

Question 7

Loop diuretics contraindications

Answer 7

Renal failure, severe hypokalaemia, severe hyponatraemia, cirrhosis, Renal impairment- high doses or rapid IV admin of loop diuretics may cause tinnitus and deafness

Furosemide and triamterene (urine mat look slightly blue in some lights)

Question 8

EXAMPLES OF WEAK POTASSIUM SPARING DIURETICS
AND AN ALDOSTERONE ANTAGONIST

Answer 8

• Amiloride, triamterene are weak diuretics
• Potassium supplements must not be given with potassium sparring diuretics
• potassium sparing diuretics and ace inhibitors can cause severe hyperkalaemia

Question 9

Aldosterone antagonists

Answer 9

Examples- spironolactone and eplerenone
- spirinalactone is a possium sparring diuretic, antagonises aldosterone
- Potassium supplements must not be given with aldosterone antagonists

Exam q- spironolactone side effectss - gynaecomastia and breast tenderness

Question 10

Other diuretics to note…

Answer 10

Combo diuretics - effective in patients with oedema resistant to one diuretics

Mannitol - is an osmotic diuretic sued to treat cerebral odema and raised ocular pressure

Mercurial diuretic- effective but hardly used due to nephrotoxicity
Acetazolamide - (carbonic anahydrase inhibitor) - weak diuretic, used for mountain sickness prophylaxis

• eye drops.- dorzolamide and brinzolamide - inhibit formation of aqueous humour and used in glaucoma