The below article was written by Robert, the moderator of this forum, to help visitors gain a fuller understanding of how Propecia and Avodart work, as well as their relative advantages and disadvantages.

Please feel free to add your comments and input by replying.


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.

Avodart – 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 at several different daily dosages. These dosages were: 0.01 mg, .05 mg, .5 mg, 2.5 mg and 5.0 mg per day. Not surprisingly, the highest dosages of 2.5 mg and 5.0 mg per day were found to achieve the highest amount of DHT suppression.

At 5.0 mg and 2.5 mg per day, Dutasteride suppresses almost 100% serum DHT. Comparatively, 5.0 mg of Finasteride per day suppresses around 70% serum DHT.

At .5 mg per day, Dutasteride still suppresses around 90% serum DHT and 55% scalp DHT. According to GSK, during both the first and second years of the two-year trial, .5 mg Dutasteride daily decreased around 92% of serum DHT concentration.

Since both inhibit 5AR, Dutasteride's list of side effects are similar to Finasteride's, but with the increased DHT inhibition comes the increased risk. Avodart's listed side effects are impotence, decrease in libido, swelling or tenderness of the breast, a decrease in the amount of semen released during sex, and allergic reactions such as rash, itching, hives, and swelling of the lips or face. Like Finasteride, Avodart should also be avoided by women.

Potential increased hair shedding for both Propecia and Avodart when first started

Many users of Finasteride and Dutasteride have reported a phenomenon known as an initial "shedding" period when first beginning treatment. This period has been reported to occur anywhere from one to six months from beginning treatment and accounts vary as to whether it returns cyclically or if it is just a one-time occurrence. It is believed that shedding occurs when the medication actually accelerates the cycle for hair follicles that are destined for the Telogen (resting) phase resulting in what appears to be an increase in hair loss.

In reality, this is regarded as a "good" sign in that it shows that the user is a responder to the medication. The shedding phase is normally temporary, lasting no more than a few weeks. When the hairs shed run through their normal resting cycle, it is generally noted that they return within a few months. There have been no conclusive studies to support this hypothesis and all evidence collected regarding shedding thus far has been anectodotal.

Possible importance of DHT in the body

Before using either dutasteride or finasteride, hair loss sufferers should also be aware that DHT actually plays an important role to play in the human body. All of DHT's effects on the body have not yet been realized and the long-term effect (>10 years) of these medications have not been clearly established. Patients are strongly cautioned that it may not be to their benefit to eliminate all traces of DHT from the body. It is also important to note that both medications are to be continued for as long as the patient wishes to keep its benefits.

Since it is believed to be better tolerated, has less of a chance of bringing on unwanted side effects, and is FDA-approved, Propecia is generally regarded as the best medication to begin with. Many men find that Propecia alone or coupled with minoxidil works great for them.

Some men will choose to try Avodart after an initial trial with Propecia. It is important to know that users should give medicines time to work before switching up. Give Propecia at least 9 months to a year before making conclusions as to its efficacy. Taking a "before/after" series of photos can be very helpful at establishing its potency. Also remember that these medications are primarily for maintaining the hair that you currently have; any regrowth is to be considered an added benefit. Realistic expectations and an optimistic, yet objective approach are important to deciding the efficacy of a medicinal hair loss regimen.

Both medications are can be effective at inhibiting the 5-alpha reductase that binds with testosterone to produce DHT. Avodart is a highly potent medication that inhibits both type I and II of the 5AR and Propecia, while also potent, only inhibits type II. When beginning any new medicinal regimen, it is best to research all areas carefully including dosage recommendations, side effects, and to adhere to the recommendations of a physician.

Continue to research hair restoration treatments and developments and share information and experiences with other hair loss sufferers at the Hair Restoration Discussion Forums and visit the Hair Transplant Network.