Prostarinol

Uses

Prostarinol is used for the treatment and control of benign prostatic hyperplasia (BPH)-

• To cause regression of the enlarged prostate
• To improve urinary flow
• To improve the symptoms associated with BPH.

Prostarinol is also used to associated treatment for these conditions: Androgenetic Alopecia, Benign Prostatic Hyperplasia (BPH), Idiopathic Hirsutism, Symptomatic Benign Prostatic Hyperplasia

How Prostarinol works

Prostarinol acts as a competitive and specific inhibitor of Type II 5α-reductase, a nuclear-bound steroid intracellular enzyme primarily located in the prostatic stromal cell that converts the androgen testosterone into the more active metabolite, 5α-dihydrotestosterone (DHT). DHT is considered to be the primary androgen playing a role in the development and enlargement of the prostate gland. It serves as the hormonal mediator for the hyperplasia upon accumulation within the prostate gland. DHT displays a higher affinity towards androgen receptors in the prostate gland compared to testosterone and by acting on the androgen receptors, DHT modulates genes that are responsible for cell proliferation. Responsible for the production of DHT together with type I 5α-reductase, the type II 5α-reductase isozyme is primarily found in the prostate, seminal vesicles, epididymides, and hair follicles as well as liver. Although finasteride is 100-fold more selective for type II 5α-reductase than for the type I isoenzyme, chronic treatment with this drug may have some effect on type I 5α-reductase, which is predominantly expressed in sebaceous glands of most regions of skin, including the scalp, and liver. It is proposed that the type I 5α-reductase and type II 5α-reductase is responsible for the production of one-third and two-thirds of circulating DHT, respectively.

The mechanism of action of Prostarinol is based on its preferential inhibition of Type II 5α-reductase through the formation of a stable complex with the enzyme in vitro and in vivo. Prostarinol works selectively, where it preferentially displays a 100-fold selectivity for the human Type II 5α-reductase over type I enzyme. Inhibition of Type II 5α-reductase blocks the peripheral conversion of testosterone to DHT, resulting in significant decreases in serum and tissue DHT concentrations, minimal to moderate increase in serum testosterone concentrations, and substantial increases in prostatic testosterone concentrations. As DHT appears to be the principal androgen responsible for stimulation of prostatic growth, a decrease in DHT concentrations will result in a decrease in prostatic volume (approximately 20-30% after 6-24 months of continued therapy). It is suggested that increased levels of DHT can lead to potentiated transcription of prostaglandin D2, which promotes the proliferation of prostate cancer cells. In men with androgenic alopecia, the mechanism of action has not been fully determined, but finasteride has shown to decrease scalp DHT concentration to the levels found in the hairy scalp, reduce serum DHT, increase hair regrowth, and slow hair loss. Another study suggests that finasteride may work to reduce bleeding of prostatic origin by inhibiting vascular endothelial growth factor (VEGF) in the prostate, leading to atrophy and programmed cell death. This may bestow the drug therapeutic benefits in patients idiopathic prostatic bleeding, bleeding during anticoagulation, or bleeding after instrumentation.

Dosage

Prostarinol dosage

The recommended dosage is one 5 mg tablet daily. Although early improvement may be seen, treatment for at least six months may be necessary to assess whether a beneficial response has been achieved. Thereafter, treatment should be continued.

Side Effects

Prostarinol is well tolerated. In clinical studies, the following adverse experiences have been reported as possibly drug related in 1% of patients treated for 12 months with 5 mg Prostarinol daily: impotence (3.7%), decreased libido (3.3%), and decreased volume of ejaculate (2.8%).

Toxicity

LD50

Oral LD50 is about 418 mg/kg in rats and there have been cases of lethality in rats receiving a single oral dose of 400 mg/kg in males and 1000 mg/kg in females.

Nonclinical toxicology

In a 24-month rat study, there were no signs of the tumorigenic potential of finasteride. In a 19-month carcinogenicity study in CD-1 mice, high doses of finasteride, at 1824 times the human exposure (250 mg/kg/day), resulted in an increase in the incidence of testicular Leydig cell adenomas and an increase in serum LH levels. In vitro mutagenesis assays demonstrated no evidence of mutagenicity. In an in vitro chromosome aberration assay, using Chinese hamster ovary cells, there was a slight increase in chromosome aberrations with much higher doses of finasteride.

Overdose

There were no reported significant adverse events in clinical trials of male patients receiving single oral doses of finasteride up to 400 mg and multiple doses of finasteride up to 80 mg/day for three months. As there have been no cases of overdose or clinically significant toxicity with finasteride, there are no specific recommendations in case of an overdose.

Significant adverse events

Common reproductive adverse events seen with finasteride therapy include erectile dysfunction, ejaculatory dysfunction, and loss of libido. These adverse events tend to disappear after discontinuation or chronic use of the drug. Only causal adverse event occurring at the male reproductive system that is caused by finasteride is decreased ejaculatory volume because of the predominant action of DHT on the prostate.

Special populations

Prostarinol can be safely used in elderly patients or those with renal impairment with no specific dosing adjustment recommendations. Prostarinol is indicated for male patients only, and it is advised that exposure to finasteride is avoided in pregnant women carrying male fetuses as it may lead to abnormal development of external genitalia in male fetuses.

Precaution

General: Since the beneficial response to Prostarinol may not be manifested immediately, patients with large residual urine volume and/or severely diminished urinary flow should be carefully monitored for obstructive uropathy.

Prostate cancer: Digital rectal examination, as well as, other evaluations for prostate cancer, should be performed on patients with BPH prior to initiating therapy with Prostarinol and periodically thereafter. Prostarinol causes a decrease in serum concentration of markers of prostatic cancer such as prostate specific antigen (PSA); therefore, reduction of serum levels of these markers in patients with BPH treated with Prostarinol does not rule out concomitant prostate cancer. No clinical benefit has yet been demonstrated in patients with prostate cancer treated with Prostarinol.

Interaction

No clinically important drug interactions have been identified. Prostarinol does not appear to significantly affect the cytochrome P450 linked drug metabolising enzyme system. Compounds which have been tested in man include Propranolol, Digoxin, Glibenclamide, Warfarin, Theophylline, and antipyrine.

Food Interaction

• Take with or without food. The absorption is unaffected by food.

Prostarinol Drug Interaction

Unknown: aspirin, aspirin, aspirin, aspirin, apixaban, apixaban, omega-3 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, tamsulosin, tamsulosin, metoprolol, metoprolol, metoprolol, metoprolol, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol

Prostarinol Disease Interaction

Moderate: liver disease, urinary obstruction

Volume of Distribution

The volume of distribution is 76 L at steady state, ranging from 44 to 96 L. Prostarinol has been shown to cross the blood brain barrier but does not appear to distribute preferentially to the CSF. It is not known whether finasteride is excreted in human milk.

Elimination Route

Prostarinol is well absorbed following oral administration and displays a slow accumulation phase after multiple dosing.[lablel] In healthy male subjects receiving oral finasteride, the mean oral bioavailability was 65% for 1 mg finasteride and 63% for 5 mg finasteride, and the values ranged from 26 to 170% for 1 mg dose and from 34 to 108% for 5 mg dose, respectively. It is reported that food intake does not affect the oral bioavailability of the drug. The peak plasma concentrations (Cmax) averaged 37 ng/mL (range, 27-49 ng/mL) and was reached 1-2 hours post administration. The AUC(0-24 hr) was 53 ngxhr/mL (range, 20-154 ngxhr/mL). The plasma concentrations and AUC are reported to be higher in elderly male patients aged 70 years or older.

Half Life

In healthy young subjects receiving finasteride, the mean elimination half-life in plasma was 6 hours ranging from 3 to 16 hours. In elderly patients over the age of 70 years, the half-life is prolonged to 8 hours.

Clearance

In healthy young subjects (n=15), the mean plasma clearance of finasteride was 165 mL/min with the range between 70 and 279 mL/min.

Elimination Route

In healthy subjects, about 32-46% of total oral dose of finasteride was excreted in the urine in the form of metabolites while about 51-64% of the dose was excreted in the feces. In patients with renal impairment, the extent of urinary excretion of finasteride is expected to be decreased while the fecal excretion is increased.

Pregnancy & Breastfeeding use

Prostarinol is contra-indicated in women who are or may become pregnant. Prostarinol is not indicated for use in women. It is not known whether finasteride is excreted in human milk.

Exposure to finasteride- risk to male fetus: Crushed or broken Prostarinol Tablets should not be handled by women who are or may become pregnant because of the possibility of absorption of finasteride and the subsequent potential risk to a male fetus. Similarly, small amounts of finasteride have been recovered from the semen in subjects receiving Prostarinol 5 mg/day. It is not known whether a male fetus may be adversely affected if his mother is exposed to the semen of a patient being treated with finasteride. Therefore, when the patients sexual partner is or may become pregnant, the patient should either avoid exposure of his partner to semen (e.g. by use of a condom) or discontinue Prostarinol.

Contraindication

Hypersensitivity to any component of this medication. Prostarinol use is also contraindicated in women and paediatric patient

Special Warning

Renal insufficiency: Dosage adjustments are not necessary in patients with renal insufficiency since pharmacokinetic studies did not indicate any change in the disposition of Prostarinol.

Hepatic insufficiency: There are no data available in patients with hepatic insufficiency.

Elderly: No dosage adjustment is required in elderly patients.

Storage Condition

Store at 20-25° C. Protect from light.

Innovators Monograph

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