What is the difference between dutasteride (Dutasteride) and finasteride (Finasteride)?

From the Guidelines

Dutasteride and finasteride are both 5-alpha reductase inhibitors used to treat benign prostatic hyperplasia (BPH), but they differ in their mechanism and potency, with dutasteride being more potent at reducing dihydrotestosterone (DHT) levels, which may provide better symptom relief for BPH patients. The key differences between dutasteride and finasteride lie in their pharmacological properties, with finasteride selectively inhibiting the 5-AR type II isoenzyme, while dutasteride inhibits both types I and II, resulting in a greater reduction of DHT levels, approximately 95% compared to finasteride's 70% reduction 1.

Mechanism of Action

• Dutasteride blocks both type I and type II 5-alpha reductase enzymes, making it more potent at reducing DHT levels
• Finasteride inhibits only type II 5-alpha reductase enzyme
• Both medications reduce DHT levels, leading to a decrease in prostate size and improvement in BPH symptoms

Clinical Effects

• Dutasteride has been shown to reduce serum DHT levels by approximately 90-95%, compared to finasteride's 70% reduction 1
• Both medications have similar side effect profiles, including sexual dysfunction, decreased libido, and rare cases of depression
• Dutasteride has a longer half-life (5 weeks versus 6-8 hours for finasteride), meaning it stays in the system longer after discontinuation

Treatment Considerations

• Patients should be aware that full effects of these medications may take 3-6 months to develop 1
• Both drugs can affect PSA levels, which should be considered during prostate cancer screening, with the measured serum PSA value being doubled after 1 year of 5-ARI therapy to accurately gauge disease progression 1
• Treatment with 5-ARIs, including dutasteride and finasteride, should be based on prostate volume and PSA threshold, with a minimum prostate volume of >30cc or PSA >1.5ng/mL necessary for a reliable response 1

From the FDA Drug Label

Finasteride, a synthetic 4-azasteroid compound, is a specific inhibitor of steroid Type II 5α -reductase, an intracellular enzyme that converts the androgen testosterone into 5α -dihydrotestosterone (DHT). Dutasteride inhibits the conversion of testosterone to DHT. DHT is the androgen primarily responsible for the initial development and subsequent enlargement of the prostate gland. Testosterone is converted to DHT by the enzyme 5 alpha-reductase, which exists as 2 isoforms, type 1 and type 2 Dutasteride is a competitive and specific inhibitor of both type 1 and type 2 5 alpha-reductase isoenzymes, with which it forms a stable enzyme complex Finasteride is 4-azaandrost-1-ene-17-carboxamide, N-(1-dimethylethyl)-3-oxo-, (5α , 17ß)-. The empirical formula of finasteride is C23H36N2O2 and its molecular weight is 372. 55. Dutasteride is chemically designated as (5α,17β)-N-{2,5 bis(trifluoromethyl)phenyl}-3-oxo-4-azaandrost-1-ene-17-carboxamide. The molecular formula of dutasteride is C27H30F6N2O2, representing a molecular weight of 528. 5

The main difference between dutasteride and finasteride is that:

• Dutasteride inhibits both type 1 and type 2 5 alpha-reductase isoenzymes.
• Finasteride is a specific inhibitor of steroid Type II 5α -reductase. Additionally, they have different molecular formulas and weights: finasteride (C23H36N2O2, 372.55) and dutasteride (C27H30F6N2O2, 528.5) 2, 3, 3.

From the Research

Comparison of Dutasteride and Finasteride

• Both dutasteride and finasteride are 5-alpha reductase selective inhibitors (5ARIs) used to treat benign prostatic hyperplasia (BPH) and other conditions related to hyperandrogenism 4.
• The primary difference between the two drugs is that finasteride blocks only the type 2 form of 5-alpha-reductase, whereas dutasteride blocks both type 1 and 2 forms of the enzyme 5.

Efficacy and Safety

• Studies have shown that both dutasteride and finasteride are effective in reducing prostate volume and improving urinary symptoms associated with BPH, with no significant difference between the two treatments 6, 7.
• A systematic review and meta-analysis found that dutasteride was better than finasteride in improving the maximum urinary flow rate (Qmax) of patients with BPH, but there was no significant difference in reducing International Prostate Symptom Score (IPSS), improving prostate volume (PV), quality of life (QOL), or serum prostate-specific antigen (PSA) level, or in the occurrence of adverse drug reactions (ADRs) 8.
• Another study found that finasteride was associated with a lower risk of prostate cancer than dutasteride in patients with BPH, although the difference was not statistically significant 5.

Mechanism of Action

• Both dutasteride and finasteride inhibit the conversion of testosterone to 5α-dihydrotestosterone (5α-DHT), which plays a crucial role in the physiological function of the neuroendocrine system 4.
• The inhibition of 5α-DHT production leads to a reduction in prostate volume and an improvement in urinary symptoms associated with BPH 4.

Clinical Applications

• Dutasteride and finasteride are commonly used to treat symptomatic BPH, and have also been used to treat other conditions such as androgenetic alopecia, acne, and hirsutism 4, 6.
• The choice of drug may depend on individual patient factors, such as the presence of other medical conditions or the risk of adverse events 6, 7.