Block 8 Drugs

Question 1

5-alpha reductase inhibitors

Answer 1

Finasteride, Dutasteride

Inhibits testosterone conversion to DHT in prostate

Anatomical reduction in prostate size -> Rx for Benign Prostatic Hypertrophy (BHP)

Question 2

Alpha blockers

Answer 2

Alpha1 and alpha2 adrenoceptor blockers -> block NA action on prostatic smooth muscle and prostatic capsule -> reduce urethral resistance in BHP

Phenoxybenzamine (historical), Prazosin (current, PBS)

+ Terazosin, Tamsulosin, Alfuzosin, Siladosin (not on PBS)

Question 3

PDE5 Inhibitors

Answer 3

Phosphodiesterase 5 inhibitors

Potentiates the effect of nitric oxide

Ingest 1 hour prior to sexual intercourse

Sildenafil, Vildenafil, Tardenafil

Rx for erectile dysfunction

Question 4

Potassium Losing Diuretics

Answer 4

LOW POTENCY: thiazides; distal tubule action

HIGH POTENCY: frusemide/LASIX; loop of Henle action

Question 5

Potassium Sparing Diuretics

Answer 5

Act on late Na-K exchange site -> reduce K+ secretion

Amiloride (block ENaC), Spironolactone (block aldosterone receptor)

Question 6

Drugs Causing Urinary Dysfunction

Answer 6

Anti-cholinergics: decrease detrusor contractility, increase sympathetic tone at internal urethral sphincter -> urinary retention

Egs. Atropine (bradycardia), ipratropium bromide (bronchodilator), tiotropium (COPD)

Anti-depressants: antagonise muscarinic receptors -> anticholinergic activity -> urinary retention

Egs. Amitriptyline

Anti-psychotics: dopamine receptor antagonists -> anticholinergic activity -> urinary retention

Egs. Chlorpromazine

Cholinomimetics: analogues of ACh -> initiates micturition & muscarinic receptors in gastro-intestinal tract -> increased intestinal motility

Egs. Bethanechol

Alpha adrenergic agonists: act on sympathetic bladder neck -> urinary retention

Egs. Pseudonephrine (hayfever)

Question 7

Oxybutynin

Answer 7

Relaxant activity on smooth muscle & antagonise muscarinic receptors -> more potent anti-spasmodic effects than atropine but less anti-Ch effects -> Rx for bladder instability (bladder hyper-reflexia)

Question 8

Azetazolamide

Answer 8

Carbonic anhydrase inhibitor

Act on proximal tubule H+/Bicarbonate exchange mechanism

Also used for glaucoma as carbonic anhydrase is also used there

Question 9

Bethanechol

Answer 9

Stable analogue of acetylcholine -> muscarinic receptors

Initiates micturition

Question 10

Pseudonephrine

Answer 10

Beta agonist (alpha and beta agonist) usually used to vasoconstrict nasal congestion

Can act on bladder neck smooth muscle and increase sphincter tone

Question 11

Prazosin Terazosin Tamsulosin

Answer 11

Alpha 1 adrenergic antagonist

Relieve prostatic smooth muscle tone for urinary retention