Avodart — dutasteride

Dutasteride is an inhibitor of the 5-alpha reductase enzyme. Reductase inhibitors are designed to prevent the conversion of testosterone to its more androgenic counterpart DHT (dihydrotestosterone). DHT is implicated in a number of disorders in men including male pattern hair loss and benign prostate enlargement. Dutasteride is specifically approved for the treatment of symptomatic benign prostate hyperplasia (BPH). While dutasteride is similar in structure and action to finasteride, it differs from the first generation reductase inhibitor in its tissue selectivity. Finasteride inhibits the type-2 isozyme of the 5- alpha reductase enzyme, found prominently in the scalp and prostate. Dutasteride is non-specific for isotype, and inhibits both type-1 and type-2 reductase. As such, it inhibits DHT conversion in all tissues including the scalp, liver, prostate, and skin. Because of this it also lowers systemic levels of DHT much more effectively than finasteride.

The DHT inhibiting effects of dutasteride make this drug of some interest to bodybuilders and athletes, particularly those concerned with the androgenic component of testosterone-based steroids. Dutasteride is capable of reducing the androgenic side effects produced by DHT conversion, changing the profile of testosterone drugs measurably. Provided moderate doses of testosterone are being used, the result can be a substantial reduction in the occurrence of oily skin and acne. For those prone to male pattern hair loss, dutasteride may also reduce the harsh impact of testosterone on the hairline. Note that as a selective type-2 inhibitor, finasteride is also effective at lowering DHT levels in the scalp (and reducing hairline impact of testosterone use), but does not work as well for reducing oily skin and acne.

In terms of overall potency, a study published in the Journal of Clinical Endocrinology and Metabolism (May 2004) directly compared dutasteride to its closest pharmaceutical counterpart, finasteride. In this investigation 399 males suffering from benign prostatic hypertrophy were assembled and separated into three general groups, each receiving dutasteride (subdivided by doses of .01, .05, .5, 2.5, or 5.0 mg daily), finasteride (.5 mg daily) or placebo, for a period of 24 weeks. Over the 24- week period, the dutasteride group noted the strongest level of DHT inhibition. The beneficial effects of this drug also occurred over a wide range of dosages. For example, a 5 mg daily amount caused 98.4% inhibition in DHT levels, while 1/10th of this amount (.5 mg daily, the adopted therapeutic dose) lowered levels by an average of 94.7%.

This was in great contrast to the 5 mg finasteride group, which noticed only 70.8% inhibition. Researchers also noted that there was significantly more of a variation in the results of the finasteride group, with some patients noting DHT suppression in the range of only 50-55%.

Just as there can be benefits to lowering 5-alpha reductase activity by way of less androgenic side effects, there can also be some drawbacks. For one, a strong androgen like DHT helps with neuromuscular interaction, fostering strength and muscle gain. Users of reductase inhibitors often report a drop in their maximum lifts soon after the drug is initiated. Libido may also decline as DHT concentrations are lowered. A small percentage of men even find the need to keep Viagra on hand, as dutasteride renders them otherwise impotent. Dihydrotestosterone also serves as a potent endogenous anti-estrogen, as this nonaromatizable steroid competes with other substrates (like testosterone, which aromatizes) to bind with the aromatase enzyme. Gynecomastia or other estrogenic side effects may occur when this competition is absent. Gynecomastia is listed in the warnings for this product, although the frequency of this in testing was very low (1.1% of users).

Brand name Avodart, Dutasteride, Avolve, Zyfetor, Duagen, Duprost

Dutasteride History

Dutasteride was first described in 1997. It was developed by the U.S. based pharmaceutical company GlaxoSmithKline. It was approved by the FDA in November 2001, and introduced to market the following year by Glaxo under the Avodart trade name. GlaxoSmithKline also markets the drug in a number of other countries in Europe and South America under the same trade name.

How is Dutasteride Supplied

Dutasteride is supplied in soft gelatin capsules containing .5 mg each.

Structural Characteristics of Dutasteride

Dutasteride is a synthetic 4-azasteroid. It has the chemical designation (5·,17‚)-N-{2,5 bis(trifluoromethyl)phenyl}-3- oxo-4-azaandrost-1-ene-17-carboxamide.

Dutasteride Warnings (Pregnancy)

This drug must never be taken during pregnancy. Be aware that dutasteride can be absorbed through the skin. Women who are, or might become pregnant, should never handle dutasteride capsules. The DHT blocking action of dutasteride can cause severe developmental problems to an unborn male fetus, even in very small amounts. Unaltered dutasteride can also be recovered in the semen. It is unknown if the drug can be absorbed during sexual intercourse enough to harm a developing male fetus. The use of condoms or abstinence is recommended during therapy.

Dutasteride Side Effects

The most common adverse reactions to dutasteride therapy are impotence, reduced libido, and difficulty ejaculating. Gynecomastia was also noted during clinical trials, but occurred in less than 1% of patients. Some patients have also developed allergic reactions to the drug, including rash, itching, edema, and hives.

Dutasteride Administration (General Considerations)

Reductase inhibitors cannot completely protect against androgenic side effects such as steroid-induced hair loss, oily skin, and acne. Reductase inhibitors lessen these side effects by reducing, not eliminating, the level of androgenic activity in the skin and scalp. Androgenic and anabolic effects are both mediated by the same receptor, and there is presently no way known to completely separate these two properties. Dihydrotestosterone is also not unique in its ability to facilitate androgenetic alopecia (male pattern hair loss). DHT inhibition, therefore, does not offer complete protection against this side effect.

Reductase inhibitors are only applicable with testosterone, methyltestosterone, and fluoxymesterone. These three drugs are converted to stronger “dihydro” derivatives by the reductase enzyme. Nandrolone and some of its derivatives become weaker upon interaction with this enzyme, as their “dihydro” metabolites bind the androgen receptor very poorly. Reductase inhibition may intensify their androgenic side effects. Methandrostenolone and boldenone undergo conversion to stronger 5-alpha reduced metabolites, but at such small levels that reductase inhibitors have little effect on their androgenicity. Most other synthetic anabolic steroids are unaffected by the reductase enzyme and reductase inhibitors.

Dutasteride Administration

When used medically for the treatment of symptomatic benign prostatic hyperplasia (BPH), dutasteride is taken in a dosage of .5 mg (1 capsule) per day.

When used by bodybuilders and athletes to reduce the androgenicity of testosterone, methyltestosterone, or fluoxymesterone, dutasteride is commonly taken in a dosage of .5 mg (1 capsule) once every 1-2 days. The drug is typically administered for as long as the offending steroids are also taken.

Dutasteride Availability

GlaxoSmithKline distributes this drug in the U.S., Europe, and South America under the Avodart trade name. Additionally, a number of other brands can be found in different markets including Austria (Avolve, Zyfetor), Greece (Duagen), India (Duprost), Netherlands (Duagen), Portugal (Duagen), and Spain (Duagen).

References

Wlliam Llewellyn (2011) - Anabolics

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