5-alpha reductase inhibitors

Question 1

1) Give the main common clinical indication for the use of 5- alpha reductase inhibitors.
2) What 3 symptoms are improved by treatment with 5-alpha reductase inhibitors?
3) What do 5-alpha reductase inhibitors reduce the need for?

Answer 1

1) In BPH as a 2nd line treatment after alpha-blockers.
2) Lower UTI symptoms such as difficulty passing urine, urinary retention and poor urinary flow.
3) They reduce the need for prostate related surgery.

Question 2

1) What do 5-alpha reductase inhibitors do?
2) Why is an alpha blocker usually preferred for initial therapy over a 5-alpha reductase inhibitor?
3) What might indicate commencement of a 5-alpha reductase inhibitor in combination with an alpha blocker?
4) What does dihydrotestosterone usually do?

Answer 2

1) They reduce the size of the prostate gland.
2) Because 5-alpha reductase inhibitors can take several months for their effect to become clinically evident.
3) If the response to an alpha-blocker is poor or if the prostate is particularly bulky.
4) Usually stimulates prostatic growth.

Question 3

Describe the basic mechanism of action of 5-alpha reductase inhibitors.

Answer 3

Inhibit intracellular enzyme 5-alpha reductase > this usually converts testosterone to dihydrotestosterone > inhibition reduces prostatic enlargement and improves urinary flow.

Question 4

1) What do the most common adverse effects of 5-alpha reductase inhibitors relate to?
2) Name 2 adverse effects of 5-alpha reductase inhibitors which are usually transient.
3) Name 2 adverse effects of 5-alpha reductase inhibitors which can commonly affect patient adherence to treatment.
4) What additional effect of androgen inhibition can be exploited to advantage in treatment of male-pattern baldness.

Answer 4

1) Their anti-androgen action.
2) Impotence and reduced libido (usually go as treatment continues).
3) Breast tenderness and breast enlargement (gynaecomastia).
4) Hair growth.

Question 5

1) What condition has been reported in men taking Finasteride?
2) What might exposure of a male foetus to 5-alpha reductase inhibitors cause?
3) In which patients are 5-alpha reductase inhibitors contraindicated?

Answer 5

1) Breast cancer.
2) Abnormal development of external genitalia.
3) Pregnant women (should not be exposed to 5-alpha reductase inhibitors - e.g. by handling broken or damaged tablets or through semen during unprotected intercourse with a man taking these drugs).

Question 6

1) What is the usual prescription of Finasteride in treatment of BPH?
2) How long might it take for the effects of Finasteride to show?
3) How should patients being treated using 5-alpha reductase inhibitors be monitored?

Answer 6

1) 5mg OD PO.
2) May take up to 6 months.
3) Follow up appointment in 3-6 months to review changes in lower UTI symptoms and development of adverse effects. Then, continue check ups every 6-12 months while treatment continues.

Question 7

In the UK, who should suspected adverse effects of drugs be reported to by:

1) Professionals?
2) The public?

Answer 7

1) Medicines and healthcare products regulatory agency (MHRA).
2) Yellow card scheme.