THE KIDNEY AND DRUGS

Question 1

What is xenobiotics?

Answer 1

a chemical compound foreign to a given biological system

Question 2

what is a steady state?

Answer 2

occurs when the amount of a drug being absorbed is the same amount that’s being cleared from the body when the drug is given continuously or repeatedly.

Question 3

where are drugs secreted into the nephron?

Answer 3

Free drug is filtered at the glomerulus and it can also be actively secreted into the proximal tubule.

Question 4

how do you measure the rate of drug clearance?

Answer 4

the concentration of urine x volume of urine

all divided by the ceontration of drug in the plasma

Question 5

how can diet affect urine pH?

Answer 5

A diet rich in citrus fruits, legumes, and vegetables produces a more alkaline urine whilst a protein-based diet produces more acidic urine

Question 6

how does urine pH affect drug clearance?

Answer 6

In alkaline urine, acidic drugs are more readily ionised.

in acidic urine, alkaline drugs are more readily ionised

Question 6

how does urine pH affect drug clearance?

Answer 6

In alkaline urine, acidic drugs are more readily ionised.

in acidic urine, alkaline drugs are more readily ionised

Question 7

how does drug ionisation affect clearance rates?

Answer 7

Ionised substances are more soluble in water so dissolve in the body fluids more readily for excretion.

Question 8

what type of drugs are mannitol and glycerin?

Answer 8

osmotic diuretics

Question 9

how do osmotic diuretics work?

Answer 9

their presence in the PCT and loop of Henle prevents the reabsorption of water, reduces plasma volume, decreases bp and increases urination

Question 10

what are the indications for osmotic diuretics?

Answer 10

decreasing inter cranial pressure, cerebral oedema, decreasing elevated intraocular pressure, acute renal failure

Question 11

when should you not give diuretics?

Answer 11

They should be used cautiously in anyone with renal dysfunction, as changes in blood flow and kidney perfusion may further compromise a diseased kidney.

Question 12

what are 2 examples of loop diuretics?

Answer 12

furosemide and bumetanide

Question 13

how do loop diuretics work?

Answer 13

they bind to Cl- binding site on the Na+/K+/2Cl- co-transporter, inhibiting it and preventing the reabsorption of Na+ and Cl-. this decreases H2O reabsorption, increasing urine production

Question 14

how fast do loop diuretics work?

why is this important?

Answer 14

they act within 1 hour and complete diuresis within 6 hours

so they can be taken twice a day and don’t interfere with sleep

Question 15

what are the indications of loop diuretics?

Answer 15

hypertension, oedema,

Question 16

what are the contra-indications of loop diuretics?

Answer 16

unuria, severe state of electrolyte depletion, hypokalaemia and hyponatraemia

Question 17

whats an example of a thiazide diuretic?

Answer 17

hydrochlorothiazide

bendroflumethiazide

Question 18

how do thiazide diuretics work?

Answer 18

they bind to the Cl- site on the Na+/Cl- co-transporter in the DCT, inhibiting it and preventing Na+ reabsorption. this decreases water reabsorption and increases urine production

Question 19

why are thiazide diuretics usually administered in the day?

Answer 19

because they take 12-24 hours to work so this reduces the chance of them interfering with sleep

Question 20

for the management of hypertension, why do we use small doses of thiazide diuretics?

Answer 20

a low dose produces a maximal blood pressure lowering effect, with very little biochemical disturbance. Higher doses cause more marked changes in electrolytes with little advantage in blood pressure control.

Question 21

what are examples of K+ sparing diuretics?

Answer 21

amiloride and spironolactone

Question 22

what are the 2 types of K+ sparing diuretics?

Answer 22

epithelial Na+ channel blockers

aldosterone antagonists

Question 23

how do epithelial Na+ channel blockers work?

Answer 23

they bind to Na+ channels in DCT and collecting tubes and block Na+ from entering into cell = increased Na+ and water excretion

Question 24

how do aldosterone inhibitors work?

Answer 24

they compete for the aldosterone receptor in the DCT, increasing Na+ and water excretion and sparing K+

Question 25

what are the indications for K+ sparing diuretics?

Answer 25

adjunct in management of hypertension, cirrhosis, and congestive heart failure

Question 26

what is a potential adverse effects of K+ sparing diuretics?

Answer 26

hyperkalaemia which can cause potentially fatal arrhythmias