Proscar (finasteride)
Last reviewed · Source: First Databank (FDB) drug data
Overview
Finasteride is aspecific inhibitor of steroid 5alpha-reductase, an intracellular enzyme necessary for conversion of testosterone to 5alpha-dihydrotestosterone (DHT).
Finasteride is a synthetic 4-azasteroid compound. The drug is a specific inhibitor of steroid Type II5alpha-reductase, an intracellular enzyme present in high concentrations in the liver, skin, and prostate gland. The conversion of testosterone to 5alpha-dihydrotestosterone (DHT) depends on the presence of this enzyme, and DHT appears to be the principal androgen responsible for stimulation of prostatic growth.
Finasteride inhibits 5alpha-reductase by forming a stable enzymecomplex; turnover from the complex is slow (half-life of about 30 days). Inhibition of 5alpha-reductase by finasteride, in a dose-dependent fashion, reduces serum and prostatic DHT concentrations substantially (by 70%), increases serum testosterone concentrations(by 10-20%, remaining withinthe physiologic range), and increases prostatic tissuetestosterone concentrations (by up to 10 times over pretreatment levels). In healthy men receiving finasteride for 2 weeks, serum DHT concentrations returned to pretreatment levels approximately 2 weeks after discontinuance of the drug.
In most patients with benign prostatic hypertrophy (BPH), prostatic volume decreases by an average of about 20-30% after 6-24 months of finasteride treatment and returns to baseline volume within several months after discontinuance of the drug; in one study of patients receiving finasteride for 3 months, prostatic volume declined by approximately 20% and returned to close to baseline valueapproximately 3 months following discontinuance of treatment. The drug also decreases serum and prostatic levels of prostate-specific antigen (PSA).
The mean bioavailability of finasteride 5-mg tablets is 63%; bioavailability is not affected by food. Peak plasma concentrations of the drug are achieved in 1-2 hours following a dose. Approximately 90% of circulating finasteride is bound to plasma proteins.
The drug has been shown to cross the blood brain barrier, but does not appear to distribute preferentially into the CSF. Finasteride is extensively metabolized in the liver, primary by cytochrome P-450 (CYP) 3A4. The mean elimination half-life of the drug in healthy individuals was 6 hours (range 3 to 16 hours).
Following administration of an oral dose, approximately 39% of the dose is excreted in urine as metabolites and 57% is ecreted in feces.
USES: Finasteride is used to shrink an enlarged prostate (benign prostatic hyperplasia or BPH) in adult men. It may be used alone or taken in combination with other medications to reduce symptoms of BPH and may also reduce the need for surgery. Finasteride may improve symptoms of BPH and provide benefits such as decreased urge to urinate, better urine flow with less straining, less of a feeling that the bladder is not completely emptied, and decreased nighttime urination.
This medication works by decreasing the amount of a natural body hormone (DHT) that causes growth of the prostate. Women and children should not use this medication.
Generic name: finasteride
Pronunciation: (fin-AS-ter-ide)
Reference product & biosimilars
No reference, biosimilar or interchangeable associated with this drug.
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Indications
The following indications are listed for Proscar:
- Benign Prostatic Hyperplasia With Lower Urinary Tract Symptom
Also known as: Symptomatic Benign Prostatic Hyperplasia, Symptomatic Benign Prostatic Hypertrophy, Symptomatic Bph, Symptomatic Prostatic Hypertrophy.
Dosing
No dosing information is available for this tab.
Finasteride is administered orally without regard to meals. The fixed combination of finasteride/tadalafil is administered orally on an empty stomach.
No dosing information is available for this tab.
No dosing information is available for this tab.
Drug interactions
Finasteride does not affect the cytochrome P-450 (CYP) enzyme system. No clinically meaningful drug interactions have been identified. Drugs that have been tested for drug interaction potential with finasteride includedigoxin, propranolol, theophylline, and warfarin.
Although specific drug interaction studies have not been performed, in clinical studies,finasteridewas used concomitantly with acetaminophen, acetylsalicylic acid, alpha-blockers, analgesics, angiotensin-converting enzyme (ACE) inhibitors, anticonvulsants, benzodiazepines, beta-blockers, calcium-channel blockers, cardiac nitrates, diuretics, H2 antagonists, HMG-CoA reductase inhibitors, nonsteroidal anti-inflammatory agents, and quinolone anti-infectives without evidence of clinically significant adverse interactions.
There are no contraindication interactions for this drug.
There are no severe interactions for this drug.
There are no moderate interactions for this drug.
Contraindications
*Pregnancy.
*Hypersensitivity to any components of the medication.
There are no contraindication contraindications for this drug.
There are no severe contraindications for this drug.
There are no moderate contraindications for this drug.
Adverse reactions
The most common adverse effects of finasteride reported in >=1% of patients in clinical studiesinclude impotence, decreased libido, decreased volume of
There are no severe adverse reactions for this drug.
There are no less severe adverse reactions for this drug.
Precautions
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Finasteride is not indicated for use in pediatric patients; safety and efficacy have not been established.
Finasteride is not indicated for use in women and is contraindicated in women who are pregnant or may potentially be pregnant. Because of the ability of 5alpha-reductase inhibitors to inhibit the conversion of testosterone to DHT, finasteride may cause abnormalities of the external genitalia of male fetuses exposed to the drug during pregnancy. Studies have shown that low doses of finasteride administered to female rats during pregnancy can produce abnormalities of the external genitalia in male offspring. If finasteride is administered during pregnancy, the patient should be apprised of the potential fetal hazard. In addition, because of the possibility of drug absorption and subsequent risk to a male fetus, women who are pregnant or who potentially may be pregnant should not handlebrokenorcrushed finasteride tablets; if such contact occurs, the affected area should be washed immediately with soap and water and the woman should inform her clinician. Intact finasteride tablets are coated, and the coating will prevent contact with finasteride during normal handling.
Reproduction studies in pregnant rats receiving finasteride dosages ranging from 100 mcg/kg daily to 100 mg/kg daily (up to 86 times the maximumrecommended human dosage (MRHD)) resulted in dose-dependent development of hypospadias in 3.6-100% of male offspring. Pregnant rats produced male offspring with decreased prostatic and seminal vesicular weights, delayed preputial separation, and transient nipple development when given dosages of 30 mcg/kg daily (0.03times the MRHD) and decreased anogenital distance when given dosages of 3 mcg/kg daily (0.003times the MRHD). The critical period during which these effects can be induced in male rats has been determined to be days 16-17 of gestation. These effects are expected pharmacologic effects of 5alpha-reductase inhibitors and are similar to those reported in male infants with a genetic deficiency of 5alpha-reductase. No abnormalities were observed in female offspring exposed to any finasteride dosage in utero.
No developmental abnormalities were observed in first filial generation (F1) male or female offspring resulting from mating of male rats receiving finasteride 80 mg/kg daily (61 times the MRHD) with untreated females. Administration of the drug at a dosage of 3 mg/kg daily (30 times the MRHD) during the late gestation and lactation period resulted in slightly decreased fertility in F1 male offspring. No effects were seen in female offspring. No evidence of malformations was observed in rabbit fetuses exposed to finasteride in utero from days 6-18 of gestation at dosages up to 100 mg/kg daily; however, effects on male genitalia would not be expected as the exposure did not occur during the critical period of genital system development in rabbits.
No abnormalities were observed in male fetuses when pregnant rhesus monkeys were given finasteride IV at dosages up to 800 ng daily (143 times the highest estimated exposure of a pregnant woman to finasteride via the semen of a sexual partner receiving finasteride 5 mg daily) during days 20-100 of gestation. However, external genital abnormalities were observed in male rhesus monkey fetuses in studies using an oral finasteride dosage of 2 mg/kg daily (18,000 times the highest estimated blood levels of finasteride from semen in men receiving 5 mg daily). No other abnormalities were observed in male fetuses, and no abnormalities were observed in female fetuses exposed to finasteride at any dosage in utero.
It is not known whether finasteride is distributed into human milk, but the drug is not indicated for use in women.
Dosage adjustment is not necessary in geriatric patients.
Because BPH occurs mainly in men 55 years of age or older, efficacy and safety of finasteride in this age group have been established, although only limited data are available on use of the drug in men older than 80 years of age. Of the 3040 patients enrolled in a long-term (4 years) controlled clinical trial of the drug, 1480 (49%) were 65 years of age or older and 105 (3.5%) were 75 years of age or older. No overall differences in efficacy or safety were observed in this trial between geriatric and younger patients, and other clinical experience has revealed no evidence of age-related differences. Generally, finasteride is well tolerated in geriatric men.
The elimination rate of finasteride is decreased in geriatric individuals; however, the findings are not clinically significant anddosage adjustment is not necessary. The mean terminal half-life of finasteride in individuals 70 years of age or older was approximately 8 hours (range: 6-15 hours) compared with 6 hours (range: 4-12 hours) in individuals 45-60 years of age; consequently, the mean daily AUC after 17 days of dosing was 15% higher in individuals 70 years of age or older.
ICD codes
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Last reviewed · Source: First Databank (FDB) drug data
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