RENAL + GU: 5-ALPHA REDUCTASE INHIBITORS

Question 1

5-AR INHIBS: INDICATIONS

Answer 1

• BPH - improve lower urinary tract symptoms such as difficulty passing urine, urinary rtn and poor urinary flow, and reduce the need for prostate related surgery

Question 2

5-AR INHIBS: MOA

Answer 2

• 5α-reductase inhibitors reduce the size of the prostate gland. They do this by inhibiting the intracellular enzyme 5α-reductase, which converts testosterone to its more active metabolite dihydrotestosterone
• As dihydrotestosterone stimulates prostatic growth, inhibition of its production by 5α-reductase inhibitors reduces prostatic enlargement and improves urinary flow
• However, it can take several months for this effect to become evident clinically
• For this reason, an α-blocker is usually preferred for initial therapy, with a 5α-reductase inhibitor added if the response is poor or if the prostate is particularly bulky

Question 3

5-AR INHIBS: ADVERSE EFFECTS

Answer 3

• The most common adverse effects of 5α-reductase inhibitors relate to their anti-androgen action
• These include impotence and reduced libido, which are usually transient, and breast tenderness and enlargement (gynaecomastia), which can affect patient adherence to treatment
• An additional effect of androgen inhibition is hair growth, which can be exploited to advantage in treatment of male-pattern baldness
• Breast cancer has been reported in men taking finasteride.

Question 4

5-AR INHIBS: WARNINGS

Answer 4

• May cause abnormal development of the external genitalia. It is therefore important that pregnant women do not take these drugs

Question 5

5-AR INHIBS: INTERACTIONS

Answer 5

• NA

Question 6

5-AR INHIBS: EXAMPLES

Answer 6

• finasteride