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PROPECIA

CLINICAL PHARMACOLOGY
Finasteride is a competitive and specific inhibitor of Type II 5?-reductase, an intracellular enzyme that converts
the androgen testosterone into DHT. Two distinct isozymes are found in mice, rats, monkeys, and humans: Type
I and II. Each of these isozymes is differentially expressed in tissues and developmental stages. In humans, Type
I 5?-reductase is predominant in the sebaceous glands of most regions of skin, including scalp, and liver. Type I 5?-
reductase is responsible for approximately one-third of circulating DHT. The Type II 5?-reductase isozyme is
primarily found in prostate, seminal vesicles, epididymides, and hair follicles as well as liver, and is responsible for
two-thirds of circulating DHT.
In humans, the mechanism of action of finasteride is based on its preferential inhibition of the Type II isozyme.
Using native tissues (scalp and prostate), in vitro binding studies examining the potential of finasteride to inhibit either
isozyme revealed a 100-fold selectivity for the human Type II 5?-reductase over Type I isozyme (IC
50
=500 and
4.2 nM for Type I and II, respectively). For both isozymes, the inhibition by finasteride is accompanied by reduction
of the inhibitor to dihydrofinasteride and adduct formation with NADP+. The turnover for the enzyme complex is slow
(t
1/2
approximately 30 days for the Type II enzyme complex and 14 days for the Type I complex).
Finasteride has no affinity for the androgen receptor and has no androgenic, antiandrogenic, estrogenic,
antiestrogenic, or progestational effects. Inhibition of Type II 5?-reductase blocks the peripheral conversion of
testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations. Finasteride
produces a rapid reduction in serum DHT concentration, reaching 65% suppression within 24 hours of oral dosing
with a 1-mg tablet.
In men with male pattern hair loss (androgenetic alopecia), the balding scalp contains miniaturized hair follicles
and increased amounts of DHT compared with hairy scalp. Administration of finasteride decreases scalp and serum
DHT concentrations in these men. The relative contributions of these reductions to the treatment effect of finasteride
have not been defined. By this mechanism, finasteride appears to interrupt a key factor in the development of
androgenetic alopecia in those patients genetically predisposed.
Finasteride had no effect on circulating levels of cortisol, thyroid-stimulating hormone, or thyroxine, nor did it affect
the plasma lipid profile (e.g., total cholesterol, low-density lipoproteins, high-density lipoproteins and triglycerides)
or bone mineral density. In studies with finasteride, no clinically meaningful changes in luteinizing hormone (LH) or
follicle-stimulating hormone (FSH) were detected. In healthy volunteers, treatment with finasteride did not alter the
response of LH and FSH to gonadotropin-releasing hormone, indicating that the hypothalamic-pituitary-testicular axis
was not affected. Mean circulating levels of testosterone and estradiol were increased by approximately 15% as
compared to baseline, but these remained within the physiologic range.
Pharmacokinetics
Following an oral dose of
14
C-finasteride in man, a mean of 39% (range, 32-46%) of the dose was excreted in
the urine in the form of metabolites; 57% (range, 51-64%) was excreted in the feces. The major compound isolated
from urine was the monocarboxylic acid metabolite; virtually no unchanged drug was recovered. The t-butyl side
chain monohydroxylated metabolite has been isolated from plasma. These metabolites possessed no more than
20% of the 5?-reductase inhibitory activity of finasteride.
In a study in 15 healthy male subjects, the mean bioavailability of finasteride 1-mg tablets was 65% (range 26-
170%), based on the ratio of AUC relative to a 5-mg intravenous dose infused over 60 minutes. Following
intravenous infusion, mean plasma clearance was 165 mL/min (range, 70-279 mL/min) and mean steady-state
volume of distribution was 76 liters (range, 44-96 liters). In a separate study, the bioavailability of finasteride was not
affected by food.
Approximately 90% of circulating finasteride is bound to plasma proteins. Buy Online Propecia has been found to cross
the blood-brain barrier.
There is a slow accumulation phase for finasteride after multiple dosing. At steady state following dosing with 1
mg/day, maximum finasteride plasma concentration averaged 9.2 ng/mL (range, 4.9-13.7 ng/mL) and was reached
1 to 2 hours postdose; AUC
(0-24 hr)
was 53 ng•hr/mL (range, 20-154 ng•hr/mL) and mean terminal half-life of
elimination was 4.8 hours (range, 3.3-13.4 hours).
Semen levels have been measured in 35 men taking finasteride 1 mg daily for 6 weeks. In 60% (21 of 35) of the
samples, finasteride levels were undetectable. The mean finasteride level was 0.26 ng/mL and the highest level
measured was 1.52 ng/mL. Using this highest semen level measured and assuming 100% absorption from a 5-mL
ejaculate per day, human exposure through vaginal absorption would be up to 7.6 ng per day, which is 750 times
lower than the exposure from the no-effect dose for developmental abnormalities in Rhesus monkeys (see
PRECAUTIONS, Pregnancy).
Page 3
The elimination rate of finasteride decreases somewhat with age. Mean terminal half-life is approximately 5-6
hours in men 18-60 years of age and 8 hours in men more than 70 years of age. These findings are of no clinical
significance, and a reduction in dosage in the elderly is not warranted.
No dosage adjustment is necessary in patients with renal insufficiency. In patients with chronic renal impairment
(creatinine clearance ranging from 9.0 to 55 mL/min), the values for AUC, maximum plasma concentration, half-life,
and protein binding after a single dose of
14
C-finasteride were similar to those obtained in healthy volunteers. Urinary
excretion of metabolites was decreased in patients with renal impairment. This decrease was associated with an
increase in fecal excretion of metabolites. Plasma concentrations of metabolites were significantly higher in patients
with renal impairment (based on a 60% increase in total radioactivity AUC). Furthermore, finasteride has been well
tolerated in men with normal renal function receiving up to 80 mg/day for 12 weeks where exposure of these patients
to metabolites would presumably be much greater.Buy Online Propecia

Propecia’s effects in detail

DHT is a derivative hormone (metabolite) of testosterone that has been shown to be critical to the initiation and progression of follicular miniaturization and eventual destruction of hair follicles in male pattern baldness. DHT is a steroid hormone just like testosterone but with greater affinity for the androgen receptor. Converting testosterone to DHT thus increases many of its effects.

While the mechanism by which DHT is involved in hair loss is not confirmed, many dermatologists and research scientists specializing in hair loss believe DHT molecules may diffuse into the interior of hair follicle cells (the cytoplasm or cytosol) and bind with androgen receptors. This complex, both the receptor and the DHT molecule, then enters the nucleus of the cell. In the nucleus of the hair follicle cell this complex could then alter the rate of protein synthesis in men who are genetically predisposed to baldness.[citation needed]

However, DHT also plays an important role in the functioning of the central nervous system (the brain), the testicles and prostate, and almost everything but muscle tissue. In muscle tissue testosterone is the dominant hormone, which is why some bodybuilders inject testosterone derivatives to aid in muscular development.

* Propecia (and other products containing finasteride) cause a rise in testosterone levels because testosterone that would normally be converted into DHT remains testosterone. Continual high levels of testosterone in the body could possibly have negative side effects.

* Artificially low levels of DHT in the body could cause some unwanted conditions. DHT is an antagonist of estrogen. Men’s bodies also produce the female hormone estrogen in the adrenal glands, although this is just one-tenth of the estrogen that premenopausal women produce in their ovaries. By reducing DHT with drugs, a man’s protection from the effects of estrogen may also be reduced. This could result in gynecomastia.

* Even though both finasteride and dutasteride were developed to combat benign prostatic hyperplasia by reducing DHT in prostate tissue, some scientists question the wisdom of using these 5-alpha reductase inhibitors in younger men who have no problem with their prostates. A research chemist, Patrick Arnold, says “Evidence is mounting that the existence of a high estrogen/androgen ratio – a condition common in older men – is highly correlated with the development of benign prostatic hyperplasia.”[citation needed] However, in apparent contradiction, individuals with 5-alpha-reductase deficiency (and thus a similar hormonal profile to users of DHT inhibitors) do not experience BPH.Buy Online Propecia

Effective Hair Loss Remedies

If you are beginning to lose your hair, you likely feel embarrassed and concerned. While hair loss is sometimes a natural part of the aging process, there are treatments that can be used to stop it. The hair loss remedy you choose will depend on many factors, including your gender, the amount of hair loss you are experiencing and the cause of your hair loss.

One popular over the counter hair loss treatment is minoxidil, which is a medication commonly known by the brand name of Regaine. Minoxidil works well for both men and women. This medication is a liquid that is rubbed on the scalp twice a day. It both increases hair growth and can stop hair loss. This hair loss remedy does not cause the hair to grow back as full, thick, and long as it had been before, but it does often cause enough hair to grow to cover the bald spot. Minoxidil does not work for everyone and the effects of the medication stop as soon as you stop using it.

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Men with male pattern baldness can benefit from a prescription hair loss remedy known as finasteride or Propecia. This medication stops testosterone from converting into dihydrotestosterone, which appears to cause male hair loss. Women cannot use this medication because it poses severe danger to male babies in the womb. Finasteride works primarily to slow or arrest the loss of hair but it can cause some new hair growth. The overall success rate of this medication is 89 per cent.

Sometimes women and men with hair loss can benefit from having cortisone injections in the scalp. Cortisone in a cream or ointment can sometimes be used to stimulate hair growth as well. However, injections are more effective than creams or ointments. The injections are usually repeated on a monthly basis.

Any medical hair loss remedy has potential side effects. Also, these medical treatments do not always work. Many people suffering from hair loss, particularly women, will try surgical procedures to treat their condition. Surgery is usually only tried after traditional remedies have failed. There are two surgical procedures used as hair loss remedies. These are hair transplants and scalp reduction surgery.

A hair transplant involves taking hair and skin from a part of the body where the hair is growing well, such as the back of the head, and surgically attaching it to the part of the head where the hair loss is occurring. As the transplants

root, the hair grows as it had been growing on the back of the head, eventually covering the bald area.

A scalp reduction involves stretching the scalp so that the skin in the bald spot can be removed. The incision is closed by stretching the scalp so that the areas that contain hair cover the removed portion. After the area heals, the hair grows as normal. There are many potential side effects to a surgical hair loss remedy. For this reason, those considering surgery to deal with their hair loss should carefully discuss the option with their doctors to give themselves the chance to weigh the benefits against the potential risks. Tags:Buy Online Propecia