Hormones 2016

Dutasteride
Pharmacodynamics
The onset is rapid, with a peak within 2–3 hours. Its mechanism of action
inhibits types I and II 5-alpha-reductase, interfering with the conversion of
testosterone to 5-α-dihydrotestosterone. It is excreted in the faeces 45% (5%
unchanged), urine < 1%, and with a half-life of about 5 weeks (Abramovitz,
2016).
Typical dosage
Pre-op - 0.5mg/day.
Post-op - Not needed.
Route
Orally.
Contraindications
Should not be taken by women, children or adolescents (BNF, 2016a).
Avodart is contraindicated in patients with hypersensitivity to dutasteride,
other 5-alpha reductase inhibitors, or any of the excipients. Avodart is also
contraindicated in patients with severe hepatic impairment (emc, 2016).
Side-effects
Genito-Urinary
• Erectile dysfunction,
• decreased libido,
• ejaculation disorder (Abramovitz,
2016).
• Semen volume decreased,
• Penile size decreased,
• urine flow decreased (rxisk,
2016b).
Other
• Gynaecomastia (Abramovitz, 2016).
• Nipple pain (rxisk, 2016b).
The most frequently observed adverse effects with Avodart were impotence
(6.0%), decreased libido (3.7%), ejaculation disorders (e.g., decrease in
volume) (1.8%), breast tenderness, and breast enlargement (1.3%). Most
of these effects tended to decrease over time (unknown, 2015b).
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