The most common side effects of dutasteride are sexual in nature. Table 1 of the FDA label pools the placebo-controlled BPH trials and reports, for months 0-6, impotence in 4.7% of men on dutasteride versus 1.7% on placebo, decreased libido in 3.0% versus 1.4%, ejaculation disorders in 1.4% versus 0.5%, and breast disorders (enlargement or tenderness) in 0.5% versus 0.2%. Reported rates fell in each later 6-month interval. Dutasteride is FDA-approved in the United States for benign prostatic hyperplasia only, so any use for hair loss is off-label.
Side Effects by Frequency
Common (1-10% of patients)
- Impotence / erectile dysfunction: 4.7% dutasteride vs 1.7% placebo, months 0-6
- Decreased libido: 3.0% vs 1.4% placebo, months 0-6
- Ejaculation disorders (decreased volume): 1.4% vs 0.5% placebo, months 0-6
- Breast disorders (breast enlargement or tenderness): 0.5% to 1.1% on dutasteride vs 0.1% to 0.3% on placebo, depending on the 6-month interval
Reported After Approval (frequency not established)
- Hypersensitivity reactions including rash, pruritus, urticaria and localized edema
- Depressed mood
Serious Reactions Reported After Approval
- Angioedema (swelling of lips, tongue, throat, face)
- Serious skin reactions
- Male breast cancer. The label states that the relationship between long-term dutasteride use and male breast neoplasia is not known
Sexual Side Effects
Sexual side effects are the most common reason patients discontinue dutasteride. In the pivotal BPH trials, reported rates were highest during the first 6 months and fell in each later interval. By months 19-24, impotence was reported by 0.8% of men on dutasteride and 0.9% of men on placebo. Full guide to sexual side effects.
Gynecomastia
Breast disorders (breast enlargement, tenderness, or both) were reported by 0.5% to 1.1% of men on dutasteride across the 6-month intervals of the pivotal BPH trials, against 0.1% to 0.3% on placebo. The usual explanation is the altered testosterone-to-estrogen ratio caused by DHT suppression. Full guide to gynecomastia.
Do Side Effects Persist After Stopping?
Reported rates of sexual adverse reactions fell over the course of the BPH trials, and the label notes that these reactions may persist after treatment is stopped, with the role of dutasteride in that persistence described as unknown. A subset of patients report symptoms that continue after stopping, a contested condition sometimes termed “post-finasteride syndrome” (PFS), which some also apply to dutasteride. Are side effects permanent? · Post-finasteride syndrome.
Side Effects in Women
The FDA label contraindicates dutasteride in pregnancy and in women of childbearing potential, because it can cause abnormalities of the external genitalia in a male fetus. Any use in women falls outside the approved labelling. Side effects in women.
⚠️ Contraindicated in Pregnancy (Teratogen): Dutasteride must never be taken by women who are pregnant or who may become pregnant. The FDA label contraindicates it in pregnancy and in women of childbearing potential, because it causes abnormalities of the external genitalia in male fetuses. Women who are pregnant or could become pregnant must not handle leaking dutasteride capsules, as the active ingredient is absorbed through the skin; if contact is made, the area should be washed immediately with soap and water. Dutasteride has a terminal elimination half-life of approximately 5 weeks, and serum concentrations remain detectable for up to 4 to 6 months after the last dose.
Long-Term Safety
Long-term safety data from the CombAT trial (4 years) and REDUCE trial (4 years) did not reveal new safety signals beyond those seen in shorter trials. Long-term safety data.
What is dutasteride? · Dosage · Dutasteride vs finasteride
Sources
- FDA. Avodart (dutasteride) prescribing information, NDA 021319 (revision s023/s025), Adverse Reactions section. accessdata.fda.gov
- FDA. Avodart (dutasteride) prescribing information, current label (revision s032), Adverse Reactions Table 1 footnote and Postmarketing Experience. accessdata.fda.gov
- Roehrborn CG, et al. The effects of combination therapy with dutasteride and tamsulosin on clinical outcomes in men with symptomatic benign prostatic hyperplasia: 4-year results from the CombAT study. Eur Urol. 2010;57(1):123-31. PubMed