Avodart Restarting After Acute Illness: A Clinical Guide to Dutasteride Interruptions
At a glance
- Drug / dutasteride 0.5 mg capsule (Avodart) [1]
- Approved use / symptomatic BPH with an enlarged prostate; hair loss is off-label [1]
- Label dose / 0.5 mg once daily, swallowed whole, with or without food [1]
- Terminal half-life / about 5 weeks at steady state [1]
- After the last dose / above 0.1 ng/mL for up to 4 to 6 months [1]
- Steady state / about 65% at 1 month, about 90% at 3 months [1]
- PSA / falls about 50% within 3 to 6 months [1]
What the label covers
The Avodart label gives one regimen, 0.5 mg once daily, swallowed whole and not chewed or opened because contact with the contents can irritate the mouth and throat, with or without food [1]. In combination use the dutasteride dose is the same, alongside tamsulosin 0.4 mg once daily [1].
How long it stays in the body
The terminal half-life is about 5 weeks at steady state, and serum levels stay above 0.1 ng/mL for up to 4 to 6 months after the last dose [1]. The label's blood donation rule reflects that persistence: men treated with Avodart should not donate blood until at least 6 months after their last dose, to avoid giving dutasteride to a pregnant transfusion recipient [1]. When daily dosing is started, serum levels reach about 65% of steady state after 1 month and about 90% after 3 months [1].
On uninterrupted dosing, median serum DHT fell 85% after 1 week and 90% after 2 weeks, and by 94% at 1 year and 95% at 3 and 4 years, while median testosterone rose about 19% to 26% and stayed within the physiologic range [1].
Medicines started during the illness
Dutasteride is extensively metabolized by CYP3A4 and CYP3A5 [1]. The label says the effect of potent CYP3A4 inhibitors on dutasteride has not been studied, and advises caution with potent, chronic inhibitors such as ritonavir [1]. Verapamil and diltiazem decrease dutasteride clearance and raise exposure, a change the label does not consider clinically significant and for which it recommends no dose adjustment [1].
PSA after a gap
Avodart lowers serum PSA by about 50% within 3 to 6 months [1]. The label says to establish a new baseline at least 3 months after starting, to double an isolated value in a man treated 3 months or more before comparing it with untreated ranges, and to evaluate any confirmed rise from the lowest on-treatment value even if it is within the normal range [1]. The label also says noncompliance with Avodart may affect PSA test results [1].
Frequently asked questions
What regimen does the Avodart label give?
How long does dutasteride stay in the body?
What do the PSA rules say around a gap?
References
- U.S. National Library of Medicine, DailyMed. Avodart (dutasteride) soft gelatin capsules, Waylis Therapeutics prescribing information. Avodart (dutasteride) soft gelatin capsules, Waylis Therapeutics label