Propecia or Avodart, which inhibits the hair loss causing effects of DHT best?

9/14/2005 2:26:59 AM

Propecia or Avodart, which inhibits the hair loss causing effects of DHT best?

Hereditary hair loss will affect about half of the American male population.  Luckily, in the past few years there have been drug treatments developed that can slow down, completely stop, or even reverse hair loss in some men.  While there is still no cure, pills such as Propecia or Avodart have given many men hope for holding on to the hair they have and maybe even regaining some of what they lost.  When considering a medicinal regimen, many hair loss sufferers find themselves asking which medication is right for them.

DHT’s role in producing hair loss

First, it is important to know what causes male-pattern baldness. The culprit to male-pattern baldness is in the genes.  Male-pattern baldness is hereditary. Myth indicates that the mothers’ side is to blame for a son’s thinning locks. But studies have shown that the genetic trait for hair loss is passed down through the genes from either parent.

Here is how hair loss actually works: The body produces an enzyme known as 5 alpha-reductase. The androgen hormone in the scalp produces testosterone.  The testosterone mixes with the 5alpha-reductase producing Dihydrotestosterone or DHT for short.  DHT is a more potent derivative of testosterone and is believed to cause male pattern baldness and when it binds to the receptor sites in hair follicles, which are genetically vulnerable to this process. Over time the DHT binding with these vulnerable receptors in the follicle slowly choke the follicles ability to produces healthy hairs. View an animation showing this hair loss process.

Propecia the current FDA approved treatments for inhibiting DHT

So far, only two medications have been approved by the Food and Drug Administration for male-pattern baldness. These drugs are minoxidil, which is marketed as “Rogaine” and finasteride, which is marketed as “Propecia”. Of these two, only finasteride actually inhibits DHT. 

Finasteride was originally distributed by pharmaceutical giant Merck & Co. in a 5 mg dose under the brand name Proscar for treatment of Benign Prostatic Hyperplasia (BPH).  In 1997, Merck was granted FDA approval for the use of finasteride as a hair loss treatment in a much smaller 1 mg version dose. This finasteride drug for use as a hair loss treatment was named Propecia.  This was a landmark event because it was the first true “baldness pill” the world had ever known.

How Propecia works to inhibit DHT

There are two types of 5 alpha-reductase (AR), type I and type II, that act as a catalyst in converting testosterone into DHT.  Propecia is a 5AR inhibitor, but only effectively inhibits Type II.  It has no known effect on type I.  Finasteride works by inhibiting the Type II 5alpha-reductase enzyme that is responsible for converting testosterone to DHT.  It is not clear as to whether only Type II 5AR is responsible for damage to hair follicles or if Type I is also to blame.  It is estimated that Propecia inhibits 70% serum DHT and 38% scalp DHT at the standard, recommended dosage of 1 mg per day.

Potential side affects of Propecia

According to Merck’s studies on the medication, around 2 percent of clinical testing participants for Propecia reported a reduction in libido. It should be noted that around 1.4% of the control group (participants that received a placebo) reported this same effect.  Other side effects of the medication listed are difficulty in achieving an erection, a decrease in the amount of semen, allergic reactions including rash, itching, hives, and swelling of the lips and face; problems with ejaculation; breast tenderness and enlargement; and testicular pain.  Because Finasteride affects the male hormone, women are strongly cautioned against using the drug since it greatly increases the risk of birth defects.

Advodart – an even stronger DHT inhibiting drug

Since the FDA approval of Propecia another DHT inhibiting drug with great potential for inhibiting hair loss has come on the scene.  This drug is called Dutasteride.

Dutasteride was developed by Glaxo-Smith Kline (GSK) and is marketed under the brand name Avodart.  Like Finasteride, Dutasteride is a 5AR inhibitor.  However, unlike Finasteride, Dutasteride inhibits both Type I AR and Type II AR.  Dutasteride also has a much longer half-life than Propecia so any side effects that occur from use of the medication will be sustained for a much longer period of time. 

Also like Proscar, Avodart is available for prescription for treatment of BPH and has FDA approval for that application.  However, testing of Dutasteride for the treatment of male-pattern baldness was discontinued by GSK for unknown reasons, though it is not thought to have been a safety issue since the drug is still available for BPH.  This means that Avodart has not yet been FDA approved for the treatment of male-pattern baldness.

Since Avodart is a dual 5AR inhibitor and is much stronger than Propecia, it is generally accepted that it is possible that it can be a more effective treatment for male patter baldness. However, without sufficient testing this is speculative. 

GSK produces Avodart in a dose of .5 mg capsules.  This is the generally prescribed dosage for the treatment of BPH.  An optimal dose for the treatment of MPB is also purely speculative at this point.  We do know the dosages used in GSK’s FDA trials.  Scientists conducting these trials studied the effects of Dutasteride a


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    All Articles by Patrick Hennessey

    Patrick is the founder of the hair transplant and the hair restoration community. He began his journey as publisher when as an early patient of the follicular unit revolution he got outstanding results and published them on the emerging Internet web in the late 1990’s. To help patients communicate with each other he started the now very popular and respected hair restoration discussion forum. He continues to act as the publisher.