Review of Pharmacology - 9E (2015)

Kidney
Explanations
1. Ans. (b) Hyperlipidemia (Ref: KK Sharma 2/e p230-231)
Thiazides cause hyperlipidemia as adverse effect and thus cannot be used to treat this condition.
Indications of thiazides:
Diuretic Uses
Hypertension (First line drugs)
Congestive heart failure
Non-diuretic Uses
Diabetes insipidus
Idiopathic hypercalciurea with Nephrocalcinosis
2. Ans. ↑ Na + ↑ K + ↓ Ca ++ (Ref: Goodman and Gilman 12/e p678)
The following table taken from Goodman and Gilman clearly explains the answer:
Excretory and Renal Hemodynamic Effects of Diuretics
Na + K + H + Ca 2+ Mg 2+ Cl – HCO3 –
Carbonic anhydrase inhibitors ↑ ↑↑ ↓ NC V ↑ ↑↑
Osmotic diuretics ↑↑ ↑ I ↑ ↑↑ ↑ ↑
Loop Diuretics ↑↑ ↑↑ ↑ ↑↑ ↑↑ ↑↑ ↑
Thiazides ↑ ↑↑ ↑ ↓ ↑ ↑ ↑
Epithelial sodium channels blockers ↑ ↓ ↓ ↓ ↓ ↑ ↑
Aldosterone antagonists ↑ ↓ ↓ I ↓ ↑ ↑
↑: Increase, ↓: Decrease, NC: No change, V: Variable change, I: Insufficient data
Do not get confused by the term ‘within 24 hours’ in the question. These are the acute effects of diuretics and these may be
modified later on by the compensatory responses of the body.
3. Ans. (b) Non-competitive and reversible carbonic anhydrase inhibitor (Ref: KDT 7/e p586)
Carbonic anhydrase inhibitors act by non-competitive but reversible inhibition of the enzyme. Examples include acetazolamide,
dorzolamide and brinzolamide.
4. Ans. (d) Impotence (Ref: Katzung 11/e p261; KDT 6/e p566-567)
Antihypertensive agents like thiazides and β-blockers can cause impotence. It is maximum with thiazides among antihypertensive
drugs and is thought to be due to volume depletion.
5. Ans. (d) Furosemide (Ref: KDT 6/e p562)
• The volume of water in urine, excreted per unit time in excess of that required to excrete the contained solutes isoosmotically
with plasma is called free water clearance.
• Free water clearance is positive for dilute urine, negative when concentrated urine is passed and zero when isotonic
urine is passed.
• To understand the effect of different diuretics on free water clearance one should known the following facts:
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The nephron of the kidney is arranged in such a way that some portion of it lies in the cortex and some portion
of it lies in the medulla.
General Kidney Pharmacology
Parts of nephron in the cortex
Proximal convoluted tubule
Distal convoluted tubule
Thick ascending limb of Henle’s loop
Cortical collecting duct
Parts of nephron in the medulla
Descending thin limb of Henle’s loop
Ascending thin limb of Henle’s loop
Medullary collecting duct
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The cortical portion of the nephron are responsible for diluting the urine (i.e., positive free water clearance).
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