Generality
Indications
Dutasteride is a second-generation inhibitor of the 5-alpha reductase enzyme because it is the first to inhibit both types (I and II) of the above enzyme.
History and Specialty recorded
Dutasteride was approved for the treatment of benign prostatic hyperplasia and related symptoms, in 2002, by the Food and Drug Administration under request of the pharmaceutical company GlaxoSmithKline.
Mechanism of action and clinical efficacy
Dutasteride, by inhibiting both types of the 5-alpha reductase enzyme, is very effective in reducing dihydrotestosterone levels, which are reduced by about 90%, compared to the average, within the first 2 weeks of treatment. In the long run the level of dihydrotestosterone decreases even more, reaching 93-94% compared to the norm within the first year from the beginning of treatment with dutasteride; the level of testosterone, its precursor, can instead increase up to 20%, always compared to the average, during treatment with dutasteride. Doctors confirm that the increase in testosterone concentration is not to be considered worrying. Although months are needed to fully benefit from the results of treatment, the efficacy of dutasteride means that there is a considerable reduction in prostate volume already after the first month of treatment; the decrease in prostate volume will continue for up to two years from the start of drug therapy.
The efficacy of dutasteride was also demonstrated by a study that included a one-year treatment of two groups of patients: one with the drug, the other with the placebo; the group of patients treated with dutasteride showed - after one year - an average reduction in prostate volume of about 24%, while in the placebo group this percentage only reached 0.5%. The reduction in prostate volume during treatment with dutasteride continues for up to two years from the start of treatment.
In another, even more complete study, which included more than 4, 000 patients with moderate to severe benign prostatic hyperplasia, always divided into two groups, the most important parameters of clinical efficacy were measured: maximum urinary flow, and the incidence of urinary retention and surgical interventions related to benign prostatic hyperplasia. This study showed that patients treated with dutasteride, after 6 months, considered the appropriate treatment; after 1 year or more the positive evaluation of the treatment was increasing. Two years after the start of the study, the urinary flow of the dutasteride group was significantly better than that of placebo-treated patients. The incidence of urinary retention also improved during the treatment: if in patients treated with placebo this incidence was higher than 4%, in patients treated with dutasteride it was 1.8%, ie less than half. The same thing applies to the incidence of surgical interventions: in patients treated with dutasteride the possibility of resorting to surgery decreases by about 50%.
Dutasteride and Androgenetic Alopecia
As for the use of dutasteride in the treatment of androgenetic alopecia, there is still not much information. After performing the phase I and II studies on the use of dutasteride against hair loss, the pharmaceutical company GlaxoSmithKline in 2002 inadvertently interrupted pharmaceutical trials without giving explanations.
The III phase studies were resumed in 2006 with a six-month study, performed in Korea, which tested the tolerability, safety and efficacy of the drug used for the treatment of androgenetic alopecia in the same doses that are used for the treatment of benign prostatic hyperplasia. Phase III studies were completed in 2009, demonstrating that dutasteride, by lowering the level of dihydrotestosterone, is a very effective drug in the treatment of androgenetic alopecia. Despite this, the pharmaceutical company GlaxoSmithKline has not yet requested approval for the marketing of dutasteride against androgenetic alopecia.
Dutasteride and Thyroid
An in-depth study of one year was carried out to ascertain the effects of dutasteride on thyroid function. At the end of this study it was observed that thyroxine levels, during dutasteride administration, remained unchanged, while TSH levels were slightly increased, still remaining within normal levels. Therefore, in conclusion, it was confirmed that the intake of dutasteride does not cause any significant change in thyroid function.
Dutasteride and Male Fertility
Another study concerning the effects of dutasteride on male fertility was performed on a group of healthy volunteers aged between 18 and 52 years. The duration of the study was one year and the post-treatment control period was 6 months. At the end of treatment with dutasteride (after one year) the average percentages of the total sperm count, seed volume and total sperm motility were measured; the values obtained were about 20% lower than the basal values for all three characteristics. However, it must be emphasized that these values, even if reduced compared to the average basal values, are in any case included in the normal range. Only two individuals who participated in the study, at the end of treatment with dutasteride, had a decrease in sperm count of about 90% compared to the baseline value, but then recovered partially after the six months of control. Therefore, although studies show that dutasteride does not cause negative effects on male fertility, the possibility that following treatment with this drug some individuals may experience reduced fertility cannot be totally excluded.
Posology and method of use
The dose of dutasteride recommended in the treatment of benign prostatic hypertrophy is 0.5 mg / day, to be taken in a single daily dose. Dutasteride capsules can be taken before or after meals. Since dutasteride comes in the form of soft gelatin capsules, containing the active ingredient in liquid form, they must be swallowed whole and must not be chewed, broken or opened; if the contents of the capsule come into contact with the oropharyngeal mucosa it may cause irritation of the same.
For the treatment of androgenetic alopecia there is not much information on the recommended dose of dutasteride to use, even if the pharmaceutical company, GlaxoSmithKline, claims that the same dose should be used as is used to treat benign prostatic hyperplasia. However, there are people who use dutasteride for the treatment of androgenetic alopecia, often without the supervision of the doctor, taking 0.5 mg of the drug, once a day or two or three times a week.
Dutasteride: side effects and contraindications »
