Drugs and the Kidney

Question 1

Name the mechanism of loop diuretics and some examples

Answer 1

Furosemide and bumetanide. It inhibits the Na/K/2Cl co-transporter in the thick ascending limb of Henle’s loop. So it reduces the osmotic gradient in the medulla of the kidney and so less water is recovered.

Question 2

What are the indications for loop diuretics

Answer 2

Oedema, resistant hypertension and hypercalcaemia. (however very strong to not often 1st choice unless there is need for powerful diuretic)

Question 3

What are the side effects of loop diuretics

Answer 3

• Hypovolaemia, hypotension,
• Electrolyte disturbances,
• Metabolic alkalosis due to loss of hydrogen ions,
• Hyperuricaemia,
• Renal impairment

Question 4

Describe the mechanism of thiazide diuretics and some examples

Answer 4

• Bendroflumethiazide and Indapamide.
• It inhibits the NaCl co-transporter in the distal tubule so less Na/Cl reabsorbed causing moderate diuresis. It has a relaxant effect on vascular smooth muscle.

Question 5

What are the indications for thiazide diuretics

Answer 5

• Hypertension,
• Mild heart failure,
• Severe resistant oedema,
• Nephrogenic diabetes insipidus

Question 6

What are some of the side effects of thiazide diuretics

Answer 6

• Hypotension, hypovolaemia,
• Low K, Na and Mg,
• Promotion of calcium retention,
• Metabolic alkalosis,
• Gout,
• Erectile dysfunction
• Hyperglycaemia, hyperlipidaemia.

Question 7

Describe the mechanism and indications and some examples of aldosterone antagonists

Answer 7

Spironolactone, eplerenone. They are potassium sparing weak diuretics which work in the CT. Indications; Oedema, hypertension and Conn’s syndrome

Question 8

What are some side effects of aldosterone antagonists

Answer 8

• Renal Impairment,
• Hyperkalaemia,
• Hyponatraemia,
• GI upset,
• Metabolic acidosis,
• Gynaecomastia with spiro

Question 9

Describe features of Amiloride

Answer 9

It is a potassium-sparing weak diuretic which acts by blocking epithelium sodium channels. Indications - oedema
Side effects - Hyperkalaemia, GI upset, metabolic acidosis and renal impairment

Question 10

Name and describe osmotic diuretics

Answer 10

Mannitol (IV) - modifies filtrate content, increasing amount of H2O excreted.
Indications - Cerebral oedema and raised intra-ocular pressure

Question 11

Name and describe carbonic anhydrase inhibitors

Answer 11

Acetazolamide (very weak diuretic)

Indications - Glaucoma and altitude sickness

Question 12

What is syndrome of inappropriate ADH secretion (SIADH) and some of its clinical signs.

Answer 12

• Excess ADH secreted by posterior pituitary gland regardless of serum osmolality. Causes hyponatraemia, low plasma osmolality, inappropriate elevated urine osmolality and euvolaemia

Question 13

What are some symptoms of SIADH

Answer 13

Mild - Nausea, vomiting, headaches, anorexia
Moderate - Muscle cramps, weakness, tremor, mental health disorders.
Severe - Drowsiness, seziures and coma

Question 14

What is SAIDH caused by?

Answer 14

• Neurological causes eg, tumour, trauma or meningitis.
• Pulmonary causes eg, pneumonia,
• Malignancy,
• Hypothyroidism,
• Drugs, eg, thiazide. loop diuretics, ACEIs, SSRIs and PPIs

Question 15

Describe the treatment of SIADH

Answer 15

Correct underlying cause, monitor plasma osmolality , serum sodium and body weight. Restrict fluids. can use Demeclocyline, tolvaptan or hypertonic sodium chloride in severe cases.

Question 16

What is Anaemia of renal disease and how is it managed?

Answer 16

Renal impairment causing less EPO = anaemia. It can be managed using erythropoietin stimulating agents (epoetin alfa) as this reduces need for blood transfusion, boasts RBC production, improves survival, reduces CV morbidity and improves QoL

Question 17

What should you consider in regards to renal function before prescribing?

Answer 17

• Degree of renal impairment,
• Acute/chronic KD?
• Proportion of drug renally excreted,
• Narrow or wide theraputic window,
• Potentially nephrotoxic?

Question 18

What are the pros and cons of estimating creatinine clearance from C&G

Answer 18

• Good validated formulae, advised for narrow theraputic index drugs.
• Inaccurate for rapidly changing creatinine levels and severe renal disease, adults only

Question 19

What are the pros and cons of using eGFR

Answer 19

Pros - Allows early detection of CKD, increasingly being used to alter drug dosing and good for majority of patients and drugs.
Cons - Not validated in some patient groups or validated drug dose calculations

Question 20

Name some examples of potentially nephrotoxic drugs

Answer 20

• ACE inhibitors,
• NSAIDs,
• Lithium,
• Digoxin,
• Aminoglycoside,
• Vancomycin,
• Metformin,
• Iodinated contrast media,
• Opioids

Question 21

what are the principles of prescribing in renal impairment

Answer 21

• check U’s and E’s, including eGFR and creatintine.
• Look at baseline and trends in renal function,
• Consider stopping or with-holding nephrotoxic drugs,
• Check resources,
• choose non-nephrotoxic drug if possible,
• reduce size of dose or increase dosing interval,
• Theraputic monitoring

Question 22

Describe the management of acute kidney injury

Answer 22

• Treat any sepsis or uro obstruction,
• Aim for good fluid/electrolyte balance,
• optimise B.P,
• With-hold/stop toxins,
• Review drug doses and side effect profile,
• Monitor U&E’s