Short answer: In the label's BPH trials, the most common Avodart side effects were sexual and mostly appeared in the first 6 months: impotence (4.7% vs 1.7% on placebo), decreased libido (3.0% vs 1.4%) and ejaculation disorders (1.4% vs 0.5%), plus breast enlargement or tenderness (0.5% to 1.1%). The label says some sexual effects may persist after stopping. There is no boxed warning.
What Avodart is approved for: Avodart is a 5 alpha-reductase inhibitor approved to treat symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate, alone or with tamsulosin: to improve symptoms and lower the risk of acute urinary retention and BPH-related surgery. It is not approved to prevent prostate cancer, and it is not approved for hair loss (section 1).
Source
AVODART (dutasteride) capsules, for oral use, prescribing information and Patient Information. Waylis Therapeutics. DailyMed, version published March 17, 2025. DailyMed setid 960797b3-09b1-4d6a-8ece-8b5d918e93e4
No. The current Avodart label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Avodart.
| Adverse Reaction | Months 0‑6 | Months 7‑12 | Months 13‑18 | Months 19‑24 |
|---|---|---|---|---|
| Impotence: Avodart | 4.7% | 1.4% | 1.0% | 0.8% |
| Impotence: Placebo | 1.7% | 1.5% | 0.5% | 0.9% |
| Decreased libido: Avodart | 3.0% | 0.7% | 0.3% | 0.3% |
| Decreased libido: Placebo | 1.4% | 0.6% | 0.2% | 0.1% |
| Ejaculation disorders: Avodart | 1.4% | 0.5% | 0.5% | 0.1% |
| Ejaculation disorders: Placebo | 0.5% | 0.3% | 0.1% | 0.0% |
| Breast disorders: Avodart | 0.5% | 0.8% | 1.1% | 0.6% |
| Breast disorders: Placebo | 0.2% | 0.3% | 0.3% | 0.1% |
Men with BPH aged 47 to 94 on Avodart 0.5 mg daily or placebo. Columns are when the reaction first started; n falls over time (Avodart 2,167 / 1,901 / 1,725 / 1,605; placebo 2,158 / 1,922 / 1,714 / 1,555). The label says the sexual reactions are linked to dutasteride and may persist after stopping; the role of dutasteride in that is unknown. Breast disorders include breast tenderness and enlargement.
4% of men on Avodart and 3% on placebo left the placebo-controlled trials because of side effects, most often impotence (1%).
With tamsulosin (CombAT trial), ejaculation disorders were 11% on the combination vs 2% on Avodart alone and 4% on tamsulosin alone. In the first 6 months: ejaculation disorders 7.8% vs 1.0% vs 2.2%, impotence 5.4% vs 4.0% vs 2.6%, decreased libido 4.5% vs 3.1% vs 2.0%.
Heart failure (composite term) after 4 years: 0.7% on the combination vs 0.1% on Avodart and 0.6% on tamsulosin; 0.6% vs 0.4% on placebo in the REDUCE trial. The label says most had other heart risk factors and no causal link has been established.
Avodart lowers PSA by about 50% within 3 to 6 months of treatment.
Reported after approval: allergic reactions including rash, itching, hives, localized swelling, serious skin reactions and angioedema; male breast cancer; depressed mood; and testicular pain and swelling.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Lower PSA readings. Avodart cuts PSA by about half within 3 to 6 months. A new PSA baseline is set at least 3 months after starting, and any confirmed rise from the lowest value may signal prostate cancer and is evaluated, even if it is in the normal range. Missed doses can also affect PSA results.
High-grade prostate cancer. In a 4-year trial of men 50 to 75, Gleason 8-10 prostate cancer was 1.0% on Avodart vs 0.5% on placebo. 5 alpha-reductase inhibitors may raise the risk of high-grade prostate cancer.
Other urological conditions. Other conditions that cause similar symptoms are considered before starting, and BPH and prostate cancer may exist together.
Risk to a male fetus. Women who are or may be pregnant should not handle Avodart capsules, because dutasteride can be absorbed through the skin. Skin contact with a leaking capsule is washed right away with soap and water.
Blood donation. Men on Avodart should not donate blood until at least 6 months after the last dose, so it does not reach a pregnant transfusion recipient.
Semen changes. Over 52 weeks, Avodart lowered total sperm count, semen volume and sperm motility compared with placebo; the drop in sperm count had not reversed 24 weeks after stopping. Values stayed in the normal range, and the effect on fertility is not known.
Who should not use it. Pregnant women, and anyone with a past clinically significant allergic reaction (such as serious skin reactions or angioedema) to Avodart or another 5 alpha-reductase inhibitor.
From the Patient Information leaflet that comes with Avodart:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.