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Pharmaceutical Name: Dutasteride
Drug Classification: Reductase Inhibitor
Active Life: 24-48 hours

Dutasteride is a reductase inhibitor initially developed and approved for medical use in the treatment of benign prostatic hyperplasia (1). This is accomplished via the inhibition of 5-alpha-reductase. 5-alpha-reductase is an enzyme, which when it interacts with testosterone , produces dihydrotestosterone (DHT). Therefore dutasteride helps in blocking the formation of DHT in users. This is important since 5-alpha-reductase is found in high concentrations in such areas of the body as the prostate and scalp. By inhibiting these interactions in these tissues dutasteride can help to reduce the levels of androgenic activity and prevent some conditions from occurring or reduce their severity.

In terms of the use of dutasteride for steroid users it would be related to the easing of several androgenic side effects often associated with the use of some anabolic and androgenic steroids. Of course due to the originally intended medical purpose of the drug, steroid users suffering from prostate conditions due to their anabolic steroid use could be well served to use a drug such as dutasteide (2). This will likely ease some of the discomfort caused by the activity of the DHT in the prostate tissue and related conditions. Similarly the androgenic activity of DHT in the scalp leading to hair loss can also prevented in some males with the use of a reductase inhibitor like dutasteride. If the hair loss experienced by the user is related to an increase in the concentration and/or level of DHT in the tissue the administration of dutasteride can help to reduce or prevent the severity of this side effect. A third side effect that the drug may help with is oily skin and/or acne. This androgenic side effect may be prevented or at the very least reduced in severity with the administration of dutasteride. However, anecdotally the results of this have been mixed to say the least and relatively few users administer the drug for this purpose.

For many these actions of dutasteride will seem very similar to that of another reductase inhibitor, namely finasteride. However these drugs do have differences. The major difference between them is that dutasteride targets both Type I and Type II 5-alpha reductase. Finasteride only targets Type II (3, 4). Type I is more heavily concentrated in the liver and skin while Type II is found most prevalently in male reproductive organs. By targeting both types of the enzyme, dutasteride is better capable of reducing more DHT then finasteride and is therefore thought to be more efficient and effective by most. Despite this, it is still not as popular as finasteride but this is likely due to dutasteride having been on the market for a much shorter time as well as not currently being approved medically for use as a preventative measure against male pattern baldness.

Interestingly, one study conducted with orally ingested testosterone accompanied by the ingestion of dutasteride resulted in a higher total serum testosterone level in those that were being administered both compounds rather then simply the testosterone itself (5). Of course this result was likely produced when the conversion of DHT was inhibited by the administration of dutasteride, but this is simply speculation. This finding is obviously premature to apply for the purposes of most anabolic steroid users. It does however offer some insight into the future use of the drug and what could be investigated, studied and used in the future.

Use/Dosing of Dutasteride

For the maximum suppression of DHT levels that dutasteride can accomplish it appears that a dose of approximately .5 milligrams per day is required. After two weeks of this dosing it has been shown that a ninety percent reduction in DHT levels in the body can be achieved (6). However many users will not require a dose that large to achieve the results that they are looking for, namely the prevention of androgenic side effects, etc. Many users will use smaller doses in the range of .25mgs every day or .5mgs every other day. However due to the active life of the compound, twenty-four to forty-eight hours, every other day dosing is as infrequently as one should administer the drug. As always users should begin using the drug at the smallest dose that delivers the results that they are looking for to ensure that the severity of the side effects of the drug are minimized.

When discontinuing the use of dutasteride there appears no need for a tapering of the drug to prevent a major rebound in DHT levels of the user. While obviously these levels will return to their normal concentrations no dramatic rise should be seen by the user. As well, at this time there appears no maximum duration that users should limit themselves to when using dutasteride. As will be described below, there are no long term side effects associated with the continuous use of this drug other then temporary sterility, however as will be explained below this condition appears to be only temporary and should not be a major concern for most users (7).

Dutasteride is administered orally with the absorption rate of the drug not being affected by the inclusion or exclusion of food or liquids with its ingestion. Users should feel free to administer the drug with or without any food they wish while also taking note that there is little suggestion that stomach discomfort will take place when ingesting the compound.

Risks/Side Effects of Dutasteride>

In terms of side effects related to the use of dutasteride, it appears that all are related to its action as a reductase inhibitor and the lack of dihydrotestosterone (DHT) circulating in the system of the user when using this drug. There are no toxicity issues related to the use of dutasteride and there have been seemingly no serious related side effects to the long term use of the drug in males (8, 9).

Despite the lack of long term side effects for users there is one significant side effect that may affect some males. This is namely temporary sterility (7). This effect does appear to be only temporary with no long term damage to the ability of the user to produce healthy sperm capable of procreation once administration of the drug ceases. However users hoping to bear children will likely have to discontinue their use of the drug to enhance their chances of success. Dutasteride is so successful at causing temporary sterility in males that it has been studied as part of a combination of drugs that could be used as male birth control. However these studies remain in their preliminary stages. In any case, many steroid users will already be experiencing temporary sterility due to their use of anabolic steroids so this will not be an additional burden for the vast majority of users.

As for the possible side effects related to the inhibition of DHT the most frequently reported side effect from use of a reductase inhibitor such as dutasteride, as reported both in the available research as well as anecdotally among anabolic steroid users, is a reduction in libido (2). This is due to DHT playing a significant role in sex drive with it also being found in high concentrations in male sex organs playing a role in their proper function. To a lesser extent some users report that their strength is reduced when using dutasteride and this can also be directly related to the drop in DHT present in the user. Similarly this may also result in a small reduction in muscle mass depending on the amount inhibited and the individual body chemistry of the user.

DHT exhibits the ability to compete for the opportunity to bind to the aromatase enzyme. If the amount of DHT is reduced this could cause an increase in the chance that estrogenic side effects (such as water retention, gynocomastia, etc.), due to less competition for the aromatase enzyme, could arise. Aromatizable compounds such as testosterone therefore have a greater likelihood to attach to this enzyme and estrogen levels could increase. While this may not be a significant problem for most users an increase in estrogenic side effects may be experienced by some who include dutasteride in their cycle(s) so greater attention may be needed to be paid to such concerns.


1. Kaplan SA. The dual 5-alpha-reductase inhibitor dutasteride induces atrophic changes and decreases relative cancer volume in human prostate. J Urol. 2006 Aug;176(2):677.

2. Evans HC, Goa KL. Dutasteride. Drugs Aging. 2003;20(12):905-16.

3. Robaire B, Henderson NA. Actions of 5alpha-reductase inhibitors on the epididymis. Mol Cell Endocrinol. 2006 May 16;250(1-2):190-5.

4. Makridakis N, Reichardt JK. Pharmacogenetic analysis of human steroid 5 alpha reductase type II: comparison of finasteride and dutasteride. J Mol Endocrinol. 2005 Jun;34(3):617-23.

5. Amory JK, Bremner WJ. Oral testosterone in oil plus dutasteride in men: a pharmacokinetic study. J Clin Endocrinol Metab. 2005 May;90(5):2610-7.

6. Llewellyn, William, Anabolics 2004, 2003-4, Molecular Nutrition, p. 260.

7. Matthiesson KL, Stanton PG, O'Donnell L, Meachem SJ, Amory JK, Berger R, Bremner WJ, McLachlan RI. Effects of testosterone and levonorgestrel combined with a 5alpha-reductase inhibitor or gonadotropin-releasing hormone antagonist on spermatogenesis and intratesticular steroid levels in normal men. J Clin Endocrinol Metab. 2005 Oct;90(10):5647-55.

8. Roehrborn C, Boyle P, Nickel J, Hoefner K, Andriole G. Efficacy and safety of a dual inhibitor of 5-alpha-reductase types 1 and 2 (dutasteride) in men with benign prostatic hyperplasia. Urology 2002 Sep;60(3):434.

9. Schulman C, Pommerville P, Hofner K, Wachs B. Long-term therapy with the dual 5alpha-reductase inhibitor dutasteride is well tolerated in men with symptomatic benign prostatic hyperplasia. BJU Int. 2006 Jan;97(1):73-9.

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