Pharmacokinetic Parameters and Mechanisms of Inhibition of Rat Type 1 and 2 Steroid 5α-Reductases: Determinants for Different In Vivo Activities of GI198745 and Finasteride in the Rat

October 2001 in “ Biochemical Pharmacology ”

J. Darren Stuart, Frank X. Lee, Deborah Simpson Noel, Sue H. Kadwell, Laurie K. Overton, Christine Hoffman, Thomas A. Kost, Timothy K. Tippin, Russell L. Yeager, Kenneth Batchelor, H. Neal Bramson

finasteride GI198745 steroid 5α-reductase type 1 steroid 5α-reductase type 2 steroid 5α-reductase dihydrotestosterone androgen-related disorders hair loss Propecia DHT

TLDR GI198745 is more potent and longer-lasting than finasteride, potentially better for treating hair loss.

The study compared the effectiveness of two drugs, GI198745 and finasteride, in inhibiting rat type 1 and 2 steroid 5α-reductases. GI198745 was found to be more potent and longer-lasting in inhibiting both enzymes, making it a potentially better treatment option for hair loss and other androgen-related disorders. The study also identified time-dependent inhibition as a factor affecting the progress curves and suggested that the drugs' different in vivo activities may be due to their pharmacokinetic parameters and mechanisms of inhibition.

View this study on sciencedirect.com →

Discuss this study in the Community →

Research cited in this study

3 / 3 results

research Inhibition of Rat Alpha-Reductases by Finasteride: Evidence for Isozyme Differences in the Mechanism of Inhibition

98 citations, April 1997 in “The Journal of Steroid Biochemistry and Molecular Biology”

Finasteride effectively blocks rat enzymes, but with varying methods and strength.

Mechanism-Based Inhibition of Human Steroid 5α-Reductase by Finasteride: Enzyme-Catalyzed Formation of NADP-Dihydrofinasteride, a Potent Bisubstrate Analog Inhibitor

research Mechanism-Based Inhibition of Human Steroid 5α-Reductase by Finasteride: Enzyme-Catalyzed Formation of NADP-Dihydrofinasteride, a Potent Bisubstrate Analog Inhibitor

136 citations, March 1996 in “Journal of the American Chemical Society”

Finasteride effectively blocks enzyme causing male pattern baldness.

research Finasteride: A Slow-Binding 5-Alpha-Reductase Inhibitor

70 citations, June 1993 in “Biochemistry”

Finasteride slowly binds to 5-alpha-reductase, affecting enzyme stability and inhibitor potency.

Related Community Posts Join

6 / 1000+ results

community From the research study: "Dihydrotestosterone and the concept of 5a-reductase inhibition in human benign prostatic hyperplasia" - G. Bartsch, R.S. Rittmaster, H. Klocker (2002) in the "World Journal of Urology".

in Research/Science 23 upvotes 2 years ago

Dutasteride is a stronger 5AR inhibitor than finasteride and can significantly lower DHT levels. Reduced doses of dutasteride may lower side effects.

community Research Backed Dutasteride Simulator (Serum/Scalp DHT included for all doses)

in Finasteride/Dutasteride 95 upvotes 4 weeks ago

A dutasteride simulator predicts that daily 0.5 mg dosing results in higher DHT suppression compared to less frequent dosing. Twice-weekly dutasteride may be as effective as finasteride 5 mg, providing a balance between efficacy and ease of use.

community Approximation of Scalp DHT Suppression Between 0.05 mg to 2.5 mg

in Research/Science 63 upvotes 10 months ago

The conversation discusses the effectiveness of various doses of Dutasteride in reducing scalp DHT and its impact on hair count. Users shared personal experiences with hair loss treatments, including Dutasteride, Finasteride, and Minoxidil, with one reporting significant hair loss reduction using a combination of oral Dutasteride and topical Minoxidil and Finasteride.

community Research Backed Dutasteride Simulator (Serum/scalp DHT included for all doses)

in Research 487 upvotes 4 weeks ago

A Dutasteride Simulator predicts serum dutasteride, serum DHT, and scalp DHT levels using models from research papers. It simulates various dosing schedules to determine steady-state effects and visualizes outcomes, including hair growth-related scalp DHT suppression.

community Topical fin formulation question

in Finasteride 91 upvotes 1 week ago

A user is making a homemade topical finasteride solution by dissolving crushed finasteride tablets in ethanol and PG. They are unsure if the final solution maintains the intended concentration after filtering and are considering adding more ethanol to ensure accuracy.

community Topical finasteride carrier/vehicle

in Finasteride 135 upvotes 3 weeks ago

The user is considering making a homemade topical finasteride solution using an ethanol-based carrier. They are inquiring if a solution containing partially denatured ethyl alcohol and benzalkonium chloride is suitable.

Related Research

3 / 3 results

research Determination of Rat 5α-Reductase Type 1 Isozyme Activity and Its Inhibition by Novel Steroidal Oxazolines

4 citations, August 2010 in “Acta Biologica Hungarica”

New steroidal compounds moderately block an enzyme related to testosterone conversion, less effectively than finasteride.

Pharmacokinetic Parameters and Mechanisms of Inhibition of Rat Type 1 and 2 Steroid 5α-Reductases: Determinants for Different In Vivo Activities of GI198745 and Finasteride in the Rat

research Pharmacokinetic Parameters and Mechanisms of Inhibition of Rat Type 1 and 2 Steroid 5α-Reductases: Determinants for Different In Vivo Activities of GI198745 and Finasteride in the Rat

22 citations, October 2001 in “Biochemical Pharmacology”

GI198745 is more potent and longer-lasting than finasteride, potentially better for treating hair loss.

research Mechanism-Based Inhibition of Human Steroid 5α-Reductase by Finasteride: Enzyme-Catalyzed Formation of NADP-Dihydrofinasteride, a Potent Bisubstrate Analog Inhibitor

136 citations, March 1996 in “Journal of the American Chemical Society”

Finasteride effectively blocks enzyme causing male pattern baldness.