Finasteride: What To Expect
Finasteride belongs to the pharmacotherapeutic groups: Testosterone-5α-reductase-inhibitors and other dermatological. At a dose of 1mg daily, it is indicated for the treatment of the first stage of the hair loss (androgenetic alopecia) in males. At the 5 mg daily dose, it is indicated for the treatment and control of benign prostatic hyperplasia (BPH).
Finasteride is not to be used by anyone under the age of 18 years.
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Mechanism of action
Finasteride is a synthetic 4-azasteroid that specifically inhibits human Type 2 5α-reductase (present within the hair follicles) thereby inhibiting the peripheral conversion of testosterone to the androgen dihydrotestosterone (DHT).
Hair Loss
In male pattern hair loss, the balding scalp contains miniaturized hair follicles with increased amounts of DHT.
Finasteride works by inhibiting a step in the process responsible for miniaturization of the scalp hair follicles, thus leading to a reversal of the balding process.
BPH
The prostate gland and, consequently, the hyperplastic prostate tissue is dependent on the conversion, of testosterone to DHT for their normal function and growth. In BPH, the enlargement of the prostate gland is dependent on the conversion of testosterone to DHT within the prostate.
Finasteride is highly effective in reducing circulating and intraprostatic DHT. Finasteride has no affinity for the androgen receptor.
Formulations
Finasteride is currently available as a generic and branded medicinal drug and is manufactured by different pharmaceutical companies. The more popular brands of Finasteride are Propecia and Proscar.
Finasteride is currently available as 1mg and 5mg film-coated tablets. However, other forms are available from special-order manufacturers. These forms include oral suspensions and powders.
Lactose monohydrate is included in the formulation of both the 1mg and 5mg tablets.
Handling and storage
Women who are pregnant or can get pregnant should not touch or handle crushed or broken tablets of Finasteride. This is because of the possibility of absorption of Finasteride and the subsequent potential risk of feminisation of a male foetus.
Can you get Finasteride on the NHS?
Finasteride is currently not prescribable in the NHS primary care for the treatment of androgenetic alopecia in men. Thus, if it is indicated for you, your doctor or prescriber would need to issue a private prescription.
As it is a Prescription Only Medicine (POM), it can only be supplied in the UK according to the instructions of a legal prescription.
How effective is Finasteride?
The best way to assess the effectiveness of any medicinal drug is to evaluate the pre- and post-marketing studies
Proscar
According to the Marketing Authorisation holder, “in clinical studies of patients with moderate to severe symptoms of BPH, an enlarged prostate on digital rectal examination and low residual urinary volumes, ‘Proscar’ reduced the incidence of acute retention of urine from 7/100 to 3/100 over four years and the need for surgery (TURP or prostatectomy) from 10/100 to 5/100. These reductions were associated with a 2-point improvement in QUASI-AUA symptom score (range 0-34), a sustained regression in the prostate volume of approximately 20% and a sustained increase in urinary flow rate.
Medical therapy of prostatic symptoms
The Medical Therapy of Prostatic Symptoms (MTOPS) Trial was a 4-to-6 year study in 3047 men with symptomatic BPH who were randomised to receive finasteride 5 mg/day, doxazosin 4 or 8 mg/day*, the combination of finasteride 5 mg/day and doxazosin 4 or 8 mg/day*, or placebo. The primary endpoint was time to clinical progression of BPH, defined as a ≥4 point confirmed increase from baseline in symptom score, acute urinary retention, BPH-related renal insufficiency, recurrent urinary tract infections or urosepsis, or incontinence. Compared to placebo, treatment with finasteride, doxazosin, or combination therapy resulted in a significant reduction in the risk of clinical progression of BPH by 34 (p=0.002), 39 (p<0.001), and 67% (p<0.001), respectively. The majority of the events (274 out of 351) that constituted BPH progression were confirmed ≥4 point increases in symptom score; the risk of symptom score progression was reduced by 30 (95% CI 6 to 48%), 46 (95% CI 25 to 60%), and 64% (95% CI 48 to 75%) in the finasteride, doxazosin, and combination groups, respectively, compared to placebo. Acute urinary retention accounted for 41 of the 351 events of BPH progression; the risk of developing acute urinary retention was reduced by 67 (p=0.011), 31 (p=0.296), and 79% (p=0.001) in the finasteride, doxazosin, and combination groups, respectively, compared to placebo. Only the finasteride and combination therapy groups were significantly different from placebo.
* Titrated from 1 mg to 4 or 8 mg as tolerated over a 3-week period”
Pharmacokinetic properties
After an oral dose of 14C-finasteride in man, it was found that 39% of the dose was excreted in the urine in the form of metabolites (virtually no unchanged drug was excreted in the urine), and 57% of the total dose was excreted in the faeces.
The oral bioavailability of Finasteride is approximately 80%, relative to an intravenous reference dose, and it is unaffected by food. Maximum plasma concentrations are reached approximately two hours after a dose of Finasteride is taken and the absorption is complete within 6-8 hours. Finasteride is approximately 93% protein bound.
In the elderly patients, the rate at which Finasteride is eliminated is somewhat decreased. The time it takes for Finasteride to fall to half its original dose (half-life) is prolonged from a mean half-life of approximately six hours in men aged 18-60 years to eight hours in men aged more than 70 years. This has no clinical significance and does not warrant a reduction in the dosage for elderly patients.
In patients with chronic renal impairment, whose creatinine clearance ranged from 9-55 ml/min, the disposition of a single dose of 14C-finasteride was not different from that in healthy volunteers. Protein binding also did not differ in patients with renal impairment. A portion of the metabolites which normally is excreted renally was excreted in the faeces. It, therefore, appears that faecal excretion increases commensurate to the decrease in urinary excretion of metabolites. Thus, dosage adjustment in non-dialysed patients with renal impairment is not essential.
There are no data available in patients with hepatic insufficiency.
Finasteride has been found to cross the blood-brain barrier. Small amounts of finasteride have been recovered in the seminal fluid of treated patients.
Propecia
According to the Marketing Authorisation holder studies were conducted in both men and women:
Studies in men
Clinical studies were conducted in 1879 men aged 18 to 41 with mild to moderate, but not complete, vertex hair loss and/or frontal/mid-area hair loss. In the two studies in men with vertex hair loss (n=1553), 290 men completed 5 years of treatment with Propecia vs. 16 patients on placebo. In these two studies, efficacy was assessed by the following methods: (i) hair count in a representative 5.1cm2 area of scalp, (ii) patient self assessment questionnaire, (iii) investigator assessment using a seven-point scale, and (iv) photographic assessment of standardised paired photographs by a blinded expert panel of dermatologists using a seven-point scale.
In these 5- year studies men treated with ‘Propecia’ improved compared to both baseline and placebo beginning as early as 3 months, as determined by both the patient and investigator assessments of efficacy. With regard to hair count, the primary endpoint in these studies, increases compared to baseline were demonstrated starting at 6 months (the earliest time point assessed) through to the end of the study. In men treated with ‘Propecia,’ these increases were greatest at 2 years and gradually declined thereafter to the end of 5 years; whereas hair loss in the placebo group progressively worsened compared to baseline over the entire 5 year period. In ‘Propecia’ treated patients, a mean increase from baseline of 88 hairs [p <0.01; 95% CI (77.9, 97.80; n=433] in the representative 5.1 cm2 area was observed at 2 years and an increase from baseline of 38 hairs [p <0.01; 95% CI (20.8, 55.6); n=219] was observed at 5 years, compared with a decrease from baseline of 50 hairs [p <0.01; 95% CI (-80.5, -20.6);n=47] at 2 years and a decrease from baseline of 239 hairs [p <0.01; 95% CI (-304.4, -173.4); n=15] at 5 years in patients who received placebo. Standardised photographic assessment of efficacy demonstrated that 48% of men treated with finasteride for 5 years were rated as improved, and an additional 42% were rated as unchanged. This is in comparison to 25% of men treated with placebo for 5 years who were rated as improved or unchanged. These data demonstrate that treatment with ‘Propecia’ for 5 years resulted in a stabilisation of the hair loss that occurred in men treated with placebo.
An additional 48-week, placebo-controlled study designed to assess the effect of ‘Propecia’ on the phases of the hair growth cycle (growing phase [anagen] and resting phase [telogen]) in vertex baldness enrolled 212 men with androgenetic alopecia. At baseline and 48 weeks, total, anagen and telogen hair counts were obtained in a 1-cm2 target area of the scalp. Treatment with ‘Propecia’ led to improvements in anagen hair counts, while men in the placebo group lost anagen hair. At 48 weeks, men treated with ‘Propecia’ showed net increases in total and anagen hair counts of 17 hairs and 27 hairs, respectively, compared to placebo. This increase in anagen hair count, compared to total hair count, led to a net improvement in the anagen-to-telogen ratio of 47% at 48 weeks for men treated with ‘Propecia’, compared to placebo. These data provide direct evidence that treatment with ‘Propecia’ promotes the conversion of hair follicles into the actively growing phase.
Studies in women
Lack of efficacy was demonstrated in post-menopausal women with androgenetic alopecia who were treated with ‘Propecia’ in a 12 month, placebo-controlled study (n=137). These women did not show any improvement in hair count, patient self-assessment, investigator assessment, or ratings based on standardised photographs, compared with the placebo group.
Pharmacokinetic properties
Relative to an intravenous reference dose, the oral bioavailability of Finasteride is around 80%. The bioavailability is not affected by the presence or absence of food. Maximum finasteride plasma concentrations are reached approximately two hours after a dose is taken orally and the absorption is complete after six to eight hours later.
Finasteride is approximately 93% protein bound.
Finasteride has been recovered in the cerebrospinal fluid (CSF), but the drug does not appear to concentrate preferentially to the CSF. A small amount of Finasteride has also been detected in the seminal fluid of subjects that received the drug.
After an oral dose of 14C-finasteride in man, 39% of the dose was found to be excreted in the urine in the form of metabolites. There was next to no unchanged drug excreted in the urine. 57% of the total dose take was excreted in the faeces.
The rate at which finasteride is eliminated decreases to some extent with age. The average terminal half-life is approximately 5 – 6 hours in men 18 – 60 years of age and 8 hours in men aged 70 years of age and older. These findings have no clinical significance, thus, a reduction in dosage in the elderly is not warranted.
No adjustment in dosage is necessary for non-dialysed patients with renal impairment.
Are there any side effects?
Propecia
The adverse reactions during clinical trials and/or post-marketing use are listed in the table below.
Frequency of adverse reactions is determined as follows:
Very Common (≥ 1/10); Common (≥ 1/100, < 1/10); Uncommon (≥ 1/1,000, < 1/100); Rare (≥1/10,000, < 1/1,000); Very rare (< 1/10,000); not known (cannot be estimated from the available data).
The frequency of adverse reactions reported during post-marketing use cannot be determined as they are derived from spontaneous reports.
| System Organ Class | Frequency: Adverse Reaction |
|---|---|
| Immune System Disorders | Not known: Hypersensitivity reactions, including rash, pruritus, urticaria and angioedema (swelling of the lips, tongue, throat and face). |
| Psychiatric Disorders | Uncommon*: Decreased libido. Uncommon: Depression†. Not known: Anxiety. |
| Cardiac Disorders | Not known: Palpitation |
| Hepatobiliary Disorders | Not known: Increased hepatic enzymes. |
| Reproductive System and Breast Disorders | Reproductive system and breast disorders: Uncommon*: Erectile dysfunction, ejaculation disorder (including decreased volume of ejaculate). Not known: Breast tenderness and enlargement, Testicular pain, infertility* |
* Incidences presented as a difference from placebo in clinical studies at Month 12.
† This adverse reaction was identified through post-marketing surveillance but the incidence in randomized controlled Phase III clinical trials (Protocols 087, 089, and 092) was not different between finasteride and placebo.
Side effects, which usually have been mild, generally have not required discontinuation of therapy.
Finasteride for male pattern hair loss has been evaluated for safety in clinical studies involving more than 3,200 men. In three 12-month, placebo-controlled, double-blind, multicentre studies of comparable design, the overall safety profiles of ‘Propecia’ and placebo were similar. Discontinuation of therapy due to any clinical adverse experience occurred in 1.7% of 945 men treated with ‘Propecia’ and 2.1% of 934 men treated with placebo.
In these studies, the following drug-related adverse experiences were reported in ≥1% of men treated with ‘Propecia’: decreased libido (‘Propecia’, 1.8% vs. placebo, 1.3%) and erectile dysfunction (1.3%, 0.7%). In addition, decreased volume of ejaculate was reported in 0.8% of men treated with ‘Propecia’ and 0.4% of men treated with placebo. Resolution of these side effects occurred in men who discontinued therapy with ‘Propecia’ and in many who continued therapy. The effect of ‘Propecia’ on ejaculate volume was measured in a separate study and was not different from that seen with placebo.
By the fifth year of treatment with ‘Propecia’, the proportion of patients reporting each of the above side effects decreased to <0.3%.
Finasteride has also been studied for prostate cancer risk reduction at 5 times the dosage recommended for male pattern hair loss. In a 7-year placebo-controlled trial that enrolled 18,882 healthy men, of whom 9060 had prostate needle biopsy data available for analysis, prostate cancer was detected in 803 (18.4%) men receiving finasteride 5 mg and 1147 (24.4%) men receiving placebo. In the finasteride 5 mg group, 280 (6.4%) men had prostate cancer with Gleason scores of 7-10 detected on needle biopsy vs. 237 (5.1%) men in the placebo group. Of the total cases of prostate cancer diagnosed in this study, approximately 98% were classified as intracapsular (stage T1 or T2). The relationship between long-term use of finasteride 5 mg and tumours with Gleason scores of 7-10 is unknown.
In addition, the following have been reported in post-marketing use: persistence of sexual dysfunction (decreased libido, erectile dysfunction and ejaculation disorder) after discontinuation of treatment with ‘Propecia’; male breast cancer (see 4.4 Special warnings and precautions for use).
Drug-related sexual undesirable effects were more common in the finasteride 1 mg-treated men than the placebo-treated men, with frequencies during the first 12 months of 3.8% vs 2.1%, respectively. The incidence of these effects decreased to 0.6% in finasteride 1 mg-treated men over the following four years. Approximately 1% of men in each treatment group discontinued due to drug-related sexual adverse experiences in the first 12 months, and the incidence declined thereafter.”
Proscar
“The most frequent adverse reactions reported are impotence and decreased libido. These adverse reactions occur early during therapy and resolve with continued treatment in the majority of patients.
The adverse reactions reported during clinical trials and/or post-marketing use are listed in the table below.
The frequency of adverse reactions is determined as follows:
Very common (≥1/10), Common (≥1/100 to <1/10), Uncommon (≥1/1,000 to <1/100), Rare (≥1/10,000 to <1/1,000), Very rare (<1/10,000), not known (cannot be estimated from the available data). The frequency of adverse reactions reported during post-marketing use cannot be determined as they are derived from spontaneous reports.
| System Organ Class | Frequency: Adverse Reaction |
|---|---|
| Immune System Disorders | Unknown: hypersensitivity reactions including swelling of the lips, tongue, throat and face |
| Psychiatric Disorders | Common: decreased libido Unknown: decreased libido that may continue after discontinuation of therapy, depression, anxiety |
| Cardiac Disorders | Unknown: palpitation |
| Hepatobiliary Disorders | Unknown: increased hepatic enzymes |
| Skin and Subcutaneous Tissue Disorders | Uncommon: rash Unknown: pruritus, urticaria |
| Reproductive System and Breast Disorders | Common: impotence Uncommon: ejaculation disorder, breast tenderness, breast enlargement. Unknown: testicular pain, sexual dysfunction (erectile dysfunction and ejaculation disorder) which may continue after discontinuation of treatment; male infertility and/or poor seminal quality. Normalization or improvement of seminal quality has been reported after discontinuation of finasteride. |
| Investigations | Common: decreased volume of ejaculate |
Medical Therapy of Prostatic Symptoms (MTOPS)
The MTOPS study compared finasteride 5 mg/day (n=768), doxazosin 4 or 8 mg/day (n=756), combination therapy of finasteride 5 mg/day and doxazosin 4 or 8 mg/day (n=786), and placebo (n=737). In this study, the safety and tolerability profile of the combination therapy was generally consistent with the profiles of the individual components. The incidence of ejaculation disorder in patients receiving combination therapy was comparable to the sum of incidences of this adverse experience for the two monotherapies.
Other Long-Term Data
In a 7 year placebo-controlled trial that enrolled 18,882 healthy men, of whom 9060 had prostate needle biopsy data available for analysis, prostate cancer was detected in 803 (18.4%) men receiving ‘Proscar’ and 1147 (24.4%) men receiving placebo. In the ‘Proscar’ group, 280 (6.4%) men had prostate cancer with Gleason scores of 7-10 detected on needle biopsy vs 237 (5.1%) men in the placebo group. Additional analyses suggest that the increase in the prevalence of high-grade prostate cancer observed in the ‘Proscar’ group may be explained by a detection bias due to the effect of ‘Proscar’ on prostate volume. Of the total cases of prostate cancer diagnosed in this study, approximately 98% were classified as intracapsular (stage T1 or T2). The relationship between long-term use of ‘Proscar’ and tumours with Gleason scores of 7-10 is unknown.
Laboratory Test Findings
When PSA laboratory determinations are evaluated, consideration should be given to the fact that PSA levels are decreased in patients treated with ‘Proscar’ (see section 4.4 Special warnings and precautions for use). In most patients, a rapid decrease in PSA is seen within the first months of therapy, after which time PSA levels stabilise to a new baseline. The post-treatment baseline approximates half of the pre-treatment value. Therefore, in typical patients treated with ‘Proscar’ for six months or more, PSA values should be doubled for comparison to normal ranges in untreated men.
For clinical interpretation see ‘Special warnings and precautions for use’, Effects on prostate-specific antigen (PSA) and prostate cancer detection.
No other difference was observed in patients treated with placebo or ‘Proscar’ in standard laboratory tests.”
Important safety information
MHRA/CHM advice: rare reports of depression and suicidal thoughts (May 2017)
The MHRA (Medicines and Healthcare products Regulatory Agency) has received reports of depression and, in rare cases, suicidal thoughts in men taking finasteride (Propecia®) for male pattern hair loss; depression is also associated with Proscar® for benign prostatic hyperplasia. Thus, patients are advised to stop taking Finasteride tablets immediately and inform a healthcare professional if they develop depression and/or have suicidal thoughts.
Conception and contraception
Finasteride is excreted in the semen and the use of a condom is recommended if the man’s sexual partner is pregnant or likely to become pregnant.
Patient and carer advice
Cases of male breast cancer have been reported in patients taking Finasteride tablets. Thus, patients and/or their carers are advised to promptly report to their doctor if they notice any changes in breast tissue such as lumps, pain, or nipple discharge.
How to report suspected adverse reactions
It is essential that even after the marketing authority has been granted to a medicine that it is continually monitored for adverse reactions. It allows for continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals and members of the public are encouraged to report any suspected adverse reactions via the Yellow Card Scheme.
If you would like to find out more about the Yellow Card Scheme, you can do so on the Medicines and Healthcare products Regulatory Agency (MHRA) website.
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References:
- https://yellowcard.mhra.gov.uk/
- https://www.medicines.org.uk/emc/search?q=finasteride
- https://bnf.nice.org.uk/drug/finasteride.html
- https://www.medicines.org.uk/emc/product/6044/smpc
- https://www.medicines.org.uk/emc/product/6062/smpc
- https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/020788s018lbl.pdf
- https://bnf.nice.org.uk/drug/finasteride.html#nationalFunding
- https://bnf.nice.org.uk/drug/finasteride.html#indicationsAndDoses
- https://www.medicines.org.uk/emc/product/1008/smpc#PHARMACOLOGICAL_PROPS
- https://www.medicines.org.uk/emc/product/2194/smpc#PHARMACOLOGICAL_PROPS
- https://www.medicines.org.uk/emc/product/1008/smpc#UNDESIRABLE_EFFECTS
- https://www.medicines.org.uk/emc/product/2194/smpc#UNDESIRABLE_EFFECTS
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