What Is Dutasteride and How Does It Work?

Dutasteride is a synthetic 4-azasteroid compound that is a selective inhibitor of both the type 1 and type 2 isoforms of steroid 5 alpha-reductase used to treat benign prostatic hyperplasia (BPH) in men with an enlarged prostate. Dutasteride helps improve urinary flow and may also reduce the need for prostate surgery later. Dutasteride is sometimes given with another medication called tamsulosin (Flomax). Dutasteride prevents the conversion of testosterone to dihydrotestosterone (DHT) in the body.

  • Dutasteride is available under the following different brand names: Avodart.

What Are Dosage of Dutasteride?

Dosage of Dutasteride:

Dosage Forms and Strengths


  • 0.5 mg

Dosing Considerations – Should be Given as Follows:

Benign Prostatic Hyperplasia

  • 0.5 mg orally once/day

Dosing Modifications

  • Renal impairment: Dose adjustment not necessary
  • Hepatic impairment: Dose adjustment not necessary
  • Pediatric: Safety and efficacy not established

What Are Side Effects Associated with Using Dutasteride?

Adverse reactions decrease with the duration of treatment, except for male breast tissue enlargement (gynecomastia).

Common side effects of dutasteride include:

  • Impotence (trouble getting or keeping an erection)
  • Decreased sexual interest/ability (libido)
  • Ejaculation disorder (decrease in the amount of semen/sperm released during sex)
  • Breast disorders (increased breast size, breast tenderness)
  • Testicle pain or swelling

Less common side effects of dutasteride include:

  • Dizziness

Other side effects of dutasteride include:

Postmarketing side effects of dutasteride reported include:

  • Immune system disorders: Hypersensitivity reactions, including rash, itching, hives, localized swelling (edema), serious skin reactions, and skin swelling
  • Neoplasms: Male breast cancer
  • Psychiatric disorders: Depressed mood
  • Reproductive system and breast disorders: Testicular pain and testicular swelling

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Dutasteride?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Dutasteride?


This medication contains dutasteride. Do not take Avodart if you are allergic to dutasteride or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately


  • Hypersensitivity
  • Women
  • Children

Short-Term Effects

  • See "What Are Side Effects Associated with Using Dutasteride?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Dutasteride?"


  • Prior to initiating treatment, rule out other urologic conditions
  • Pregnant women should avoid handling capsules due to the risk of absorption through the skin
  • Obstructive uropathy, liver disease
  • The patient should not donate blood until 6 months after the last dose of dutasteride
  • Dutasteride lowers serum prostate-specific antigen (PSA) 40-50%; establish new baseline PSA after 3-6 months of treatment
  • Monitor for cardiac changes or cardiac failure
  • 5-ARIs and prostate cancer risk:
    • June 9, 2011: Recent data from 2 large, randomized, controlled trials observed an increased risk of being diagnosed with a more serious form of prostate cancer (high-grade prostate cancer) in trial participants taking 5-alpha reductase inhibitors (5-ARIs)
    • The 2 trials are the Prostate Cancer Prevention Trial (PCPT) and the Reduction by Dutasteride of Prostate Cancer Events (REDUCE) trial
    • The revised prescribing information recommends that prior to initiating therapy with 5-ARIs, appropriate evaluation should be performed to rule out other urologic conditions, including prostate cancer, that might mimic benign prostatic hyperplasia

Pregnancy and Lactation

  • Do not dutasteride use in pregnancy. The risks involved outweigh potential benefits
  • Safer alternatives exist
  • Pregnant women should avoid handling capsules due to the risk of absorption through the skin
  • Dutasteride excretion in milk is unknown. Its use is contraindicated if breastfeeding
Medscape. Dutasteride.
RxList. Avodart Side Effects Center.

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