Dutasteride vs. Finasteride: Similarities & Differences

Medically reviewed by Femi Aremu, PharmD

Dutasteride (brand name: Avodart) and finasteride (brand names: Propecia, Proscar) are broadly similar, orally administered prescription drugs classified as 5-alpha reductase inhibitors (otherwise known as DHT [dihydrotestosterone] blockers).

Healthcare providers prescribe 5-alpha reductase inhibitors to treat the symptoms of benign prostatic hyperplasia (BPH), also called an enlarged prostate.

While the Food and Drug Administration (FDA) has only approved dutasteride for males with BPH, some healthcare providers may prescribe it off-label for hair loss.

Conversely, finasteride is FDA-approved for treating BPH and hair loss, although at different dosages. Finasteride also has more clinical evidence supporting its effectiveness for hair loss than dutasteride.

This is one of the key differences between the two drugs.

You can read on to learn more about the differences and similarities between dutasteride and finasteride, including their dosing, side effects, and effectiveness for BPH or hair loss.

Understanding BPH

The prostate is a gland in the male reproductive system. It is located near the urethra, the tube through which urine and semen leave the body.

BPH occurs when the prostate gland enlarges, affecting the urethra’s normal functions. BPH symptoms often include frequent urination, trouble with urine flow, and painful urination.

BPH is uncommon among males under 35, but its likelihood increases with age. It's estimated that up to 50% of men over 60 have an enlarged prostate to some degree.  

What Is Dutasteride?

Dutasteride is a generic prescription drug. It comes as a 0.5-milligram (mg) oral capsule.

Dutasteride, or the brand-name version Avodart, is approved by the FDA to reduce the symptoms of BPH in adult males.

It’s also indicated to lower the risk of urinary retention, or trouble completely emptying your bladder, and decrease the chances of needing surgery for BPH.

Note that dutasteride is not meant to help prevent prostate cancer and is not FDA-approved for this purpose.

Dutasteride and Flomax (tamsulosin) are often prescribed together to reduce BPH symptoms. Flomax is a type of drug called an alpha-blocker, a type of medicine that can be used to treat an enlarged prostate (benign prostatic hyperplasia).

Dutasteride is also used alongside other active ingredients, such as in Jalyn (dutasteride/tamsulosin). Jalyn is a two-in-one combination drug used to treat an enlarged prostate.

How Does Dutasteride Work?

Dutasteride works to block the conversion of testosterone into another compound called DHT, a sex hormone. Usually, testosterone is converted into DHT by the enzyme 5-alpha reductase.

When too much testosterone gets converted into DHT, the prostate may enlarge and lead to BPH symptoms.

Dutasteride’s mechanism of action is to inhibit (block) the 5-alpha reductase enzyme, which in turn blocks the formation of DHT. This helps decrease the prostate's size and reduce the related symptoms of BPH.

Dutasteride begins working immediately but doesn’t reduce BPH symptoms immediately. It may take one to two weeks to notice an improvement.

Dutasteride is meant to be taken as a long-term treatment. Remember that dutasteride has a long half-life (the time required for the amount of a drug's active substance in the body to fall by half).

If you stop taking dutasteride, some level of the drug remains in your system for about four to six months after your last dose.

What Is Finasteride?

Finasteride is a generic prescription drug that is administered via an oral tablet.

There are two brand-name versions of finasteride: Proscar and Propecia. They have different dosages and are approved by the FDA for different conditions.

Proscar (finasteride 5-mg) is prescribed to treat BPH symptoms in adult males.

Like dutasteride, Proscar is also FDA-approved to lower the risk of urinary retention and reduce the chances of needing BPH-related surgery, such as transurethral resection of the prostate (TURP, cutting away a section of the prostate).

Finasteride and doxazosin, an alpha-blocker, are often prescribed to reduce BPH symptoms.

The FDA has approved the 1-mg tablet of finasteride (Propecia) to treat male-pattern hair loss in adult men, known as androgenetic alopecia (balding).

The drug is not approved for females. And finally, know that finasteride is not FDA-approved for prostate cancer prevention.

How Does Finasteride Work?

Finasteride and dutasteride work in a similar way to treat BPH symptoms. As a 5-alpha reductase inhibitor, finasteride blocks the conversion of testosterone into DHT.

By lowering DHT levels, finasteride helps to reduce prostate enlargement. However, finasteride only inhibits part of the conversion, whereas dutasteride completely blocks conversion. DHT levels typically remain higher during finasteride treatment than dutasteride.

Another difference is how long finasteride takes to work for BPH. Unlike dutasteride, finasteride produces a rapid effect, working to reduce DHT levels within eight hours of the first dose.

This means finasteride typically provides a quicker reduction in BPH symptoms than dutasteride.

However, finasteride takes a while to start working for hair loss. Daily treatment may take three months or longer before you notice any benefit.

Finasteride has a shorter half-life than dutasteride. If you stop taking finasteride, the effects of the drug wear off within two weeks.

Dosage Comparison

The table below reviews the dosage forms, strengths, and recommended dosing for dutasteride and finasteride.

Your healthcare provider may recommend a different dosage. Be sure to follow their instructions:

Comparing Efficacy

You may be wondering if dutasteride or finasteride is more effective for BPH.

The short answer is that both are similar in how well they work for reducing BPH symptoms. Finasteride starts working more quickly, but dutasteride generally shrinks the prostate more.

When comparing the clinical trial results of dutasteride and finasteride, the main difference is how each drug works to lower DHT levels in the body.

When DHT levels become too high, the prostate enlarges and causes urination problems.

Since dutasteride completely blocks the conversion of testosterone to DHT, while finasteride only partially blocks this conversion, DHT levels are typically lower with dutasteride treatment versus finasteride treatment.

However, this difference didn't change how well the two medications worked for reducing prostate size and BPH symptoms.

In clinical trials, dutasteride made the prostate 25% smaller, while finasteride made it 18% smaller. These size reductions helped improve urine flow (2.2 milliliters [mL] per second improvement with dutasteride and 1.7 milliliters per second with finasteride).

In these trials, treatment with either medication led to similar improvements in BPH symptoms.

While healthcare providers might prescribe dutasteride off-label for managing hair loss, it doesn’t have FDA approval for this indication. In contrast, finasteride has received FDA approval for treating hair loss and BPH.

As such, when it comes to hair loss, finasteride is backed by more extensive clinical evidence than dutasteride for this purpose.

Alternative Treatment Options for BPH

While prescription medication effectively reduces urinary symptoms associated with BPH, several lifestyle changes may also help reduce the severity of the symptoms.

Experts recommend the following tips to help reduce urination problems due to an enlarged prostate:

• Drink less fluid in the evening to reduce the number of sleep disruptions for needing to urinate at night

• Avoid or reduce intake of caffeine and alcohol

• Increase physical activity

Some people prefer to try herbal remedies for prostate health before pursuing prescription treatments. Some evidence suggests that saw palmetto and African cherry might benefit men with mild BPH symptoms and improve urinary symptoms.

However, herbs might not work as well as dutasteride and finasteride, especially if your urination symptoms are more than mildly bothersome.

Before seeing palmetto or other dietary supplements while taking dutasteride or finasteride, please consult a healthcare provider to ensure it is safe.

Side Effects & Safety

Most of the common side effects of dutasteride and finasteride are sexual. This is because of how the drugs work to reduce the levels of DHT.

More common side effects of dutasteride include:

• Erectile dysfunction (also known as impotence)

• Decreased libido

• Reduced volume of ejaculate

• Other ejaculation disorders

• Gynecomastia (enlargement of male breast tissue)

• Dizziness

• Rash

Both drugs can cause sexual side effects, but dutasteride might have a slightly higher risk due to its more substantial effect on lowering DHT levels.

Most of the common side effects, such as erectile dysfunction, can typically be managed with other medications, such as Viagra (sildenafil).

Suppose you and your healthcare provider decide that you’ll stop taking finasteride or dutasteride. In that case, these side effects should disappear, and your sexual function should eventually return to what it was before you started the medication.

Precautions

People with a history of an allergic reaction to dutasteride or finasteride should avoid these products. Also, these drugs are not meant to be taken by females or children.

Pregnant people should not touch dutasteride capsules or finasteride tablets, especially if they are broken. Taking or touching the medication while pregnant can expose a developing fetus to the drug and cause harmful effects.

Dutasteride and finasteride can lower prostate-specific antigen (PSA) levels. Healthcare providers also check PSA levels to see if someone might have prostate cancer.

Since both medications can lower PSA levels, healthcare providers need to adjust how they interpret PSA test results in someone taking dutasteride or finasteride to accurately determine the possibility of prostate cancer.

During clinical trials, long-term use of dutasteride or finasteride was associated with an increased risk of high-grade prostate cancer in males 55 and older.

While the exact effect dutasteride and finasteride may have on cancer development remains unclear, it is essential to understand the potential risk before taking either drug.

Potential for Interaction

Interactions with other drugs can affect how well these medications work or increase the risk of side effects.

Also, herbal supplements that affect hormones might interact with finasteride or dutasteride, potentially impacting their intended effects.

Here are some examples of interactions with finasteride and dutasteride:

• Alpha-Blockers: Combining alpha-blockers with finasteride might have an additive effect on reducing blood pressure, so monitoring blood pressure is essential, especially when combination treatment is started or after dosage increases.

• Cytochrome P450 Inhibitors. Some drugs that inhibit (block or slow) the cytochrome P450 enzyme system might affect how finasteride is metabolized in the body, potentially altering its effectiveness or causing adverse effects. Examples include grapefruit and Norvir (ritonavir).

Also, finasteride and dutasteride are 5-alpha reductase inhibitors and shouldn’t be combined. Taking both drugs together could lead to an increased risk of side effects.

Remember that this is not a complete list; other interactions are possible.

Always consult your healthcare provider or pharmacist before starting or changing any medications, including finasteride and dutasteride, to help prevent harmful interactions.

Summary

Finasteride and dutasteride are similar prescription drugs. They work to reduce prostate size by blocking the conversion of testosterone to DHT.

Both drugs are similarly effective for reducing BPH-related urinary problems (enlarged prostate). Both drugs may be used as a treatment for hair loss in men, but finasteride is more commonly prescribed for this purpose and has more evidence backing this use.

Both drugs can cause sexual side effects, but dutasteride might have a slightly higher risk.

Talk to a healthcare provider to determine if one of these medications may benefit you.

Frequently Asked Questions

How do I store dutasteride vs. finasteride?

Dutasteride and finasteride should be kept in a dry place at room temperature. Importantly, these medications may be absorbed through the skin.

As such, people who may be pregnant or have a history of allergic reactions to either product should not touch finasteride tablets or dutasteride capsules, especially if they are crushed or broken.

Are any blood tests necessary while taking dutasteride or finasteride?

Dutasteride and finasteride can affect PSA levels. Because of this, individuals taking either drug should have their PSA levels monitored.

Healthcare providers typically order PSA tests after six months of treatment and periodically after that.

Also, since having BPH is linked to an increased risk of prostate cancer, people treated for BPH should see their healthcare provider or urologist for regular monitoring, including blood work and physical exams.

Can BPH lead to cancer?

BPH may increase the risk of prostate and bladder cancer. While the exact role BPH plays in these cancers remains unknown, the inflammation involved in BPH is also associated with cancer development.

People with more aggressive BPH (symptoms that start and worsen very quickly) seem to have a higher risk of developing prostate cancer.

Read the original article on Verywell Health.