Diuretics

Question 1

What are the uses of diuretics? (6)

Answer 1

• treatment and control of systemic oedema
• management of localised oedema
• improve urine flow (acute renal failure)
• treat certain endocrinopathies
• Exercise induced pulmonary haemorrhage (horses)
• Hypertension (humans??)

Question 2

What are the classes of diuretics?

Answer 2

• loop diuretics
• thiazidines
• potassium sparing
• carbonic anyhydrase inhibitors (CAI)
• osmotics

Question 3

What are the pharmacokinetic properties of loop diuretics? (7)

Answer 3

• sulphonamide derivatives
• secreted into PCT
• act on ascending loop to inhibit Na/K/2Cl co transporter which results in loss of these ions along with water in urine
• POTENT!
• they will also increase renal PG which increase renal blood flow (systemic venodilator)
• rapid onset
• lasts 4-6 hours

Question 4

Do loop diuretics have any side effects?

Answer 4

YES

• dehydration
• pre renal azotemia
• electrolyte disturbances
• ototoxicity when used with aminoglycosides

Question 5

What are the pharmacokinetic properties of Thiazidines? (6)

Answer 5

• secreted into PCT
• act in DCT to block Na/Cl reabsorption causing loss of Na, H, Cl, Mg and K with water in urine.
• dependent on renal PG production as ineffective with low renal blood flow
• mild-moderate potency
• slower onset but longer lasting
• no vet license

Question 6

How are thiazidines used?

Answer 6

• as an add on to furosemide (loop diuretic)

- in nephrotoxic diabetes insipidus

Question 7

Do Thiazidines have any side effects?

Answer 7

YES

• dehydration
• pre renal azotemia
• electrolyte disturbances
• ototoxicity when used with aminoglycosides
• alkalosis
• insulin resistance

Question 8

What are the pharmacokinetic properties of K sparing?

Answer 8

• inhibits Na/H exchanger which decreased K loss indirectly.
• spirinolactone and epterenae (SP???) are competitive aldosterone anatagonists
• weak

Question 9

When are K sparing used?

Answer 9

• in combination is other diuretics to reduce hyperkalaemia

- for ascites due to hepatic diseases

Question 10

What are the pharmacokinetic properties of CAIs? (2)

Answer 10

• secreted into PCT

- inhibit tubular production of H for Na/H exchanger leading to an increase in NAHCO3 and water (and K) excretion

Question 11

What are CAIs used for?

Answer 11

• topically for glaucoma in cats and dogs

- weak diuretics systemically; not often used

Question 12

Are there any side effects for CAIs?

Answer 12

YES

-acidosis

Question 13

What are the pharmacokinetic properties of osmotic diuretics?

Answer 13

filtered and effective mainly in the PCT and loop

Question 14

Mannitol is an osmotic diuretic. What would it be used for and why?

Answer 14

-pulmonary oedema/ increase ICP
-it moves fluid into plasma
(also topically for glaucoma but not common so dinnae fret)

Question 15

Are there any side effects for osmotic diuretics?

Answer 15

NO: not according to me notes anyway.

Question 16

Are there any contraindications for osmotic diuretics?

Answer 16

YES.

congestive HF and other generalised oedemas as it increase plasma volume.

Question 17

What are the general side effects for diuretics?

Answer 17

• dehydration
• pre renal azotemia
• disturbance of electrolytes
• hyponatraemia
• hypomagnesaemia
• incontinnence
• increase in thirst
• increase in urination

Question 18

What can cause resistance of diuretics?

Answer 18

• decreased renal blood flow
• hormonal activation (RAAs, aldosterone)
• hypertrophy in DC tubular cells: increase in ion transport capacity

Question 19

How could you improve the efficacy of diuretics?

Answer 19

• improve compliance
• improve cardiac function and treat arrhythmias/excessive heart rates
• increase dose/frequency
• give by IV/continuous infusion
• add ACE inhibitors +/- spirinolactones
• use sequential nephron blockade