OverviewDosageSide EffectsInteractionsHalf-Life

The following serious adverse reactions of finasteride are discussed in greater detail in other sections:

  • Impotence
  • Decreased libido
  • Decreased volume of ejaculate
  • Breast enlargement
  • Breast tenderness and rash

Adverse Reactions

Clinical Trials Experience

Finasteride is generally well tolerated; adverse reactions usually have been mild and transient.

4-Year Placebo-Controlled Study (PLESS)

In PLESS, 1524 patients treated with finasteride and 1516 patients treated with placebo were evaluated for safety over a period of 4 years. The most frequently reported adverse reactions were related to sexual function. 3.7% (57 patients) treated with finasteride and 2.1% (32 patients) treated with placebo discontinued therapy as a result of adverse reactions related to sexual function, which are the most frequently reported adverse reactions.

Table 1 presents the only clinical adverse reactions considered possibly, probably or definitely drug-related by the investigator, for which the incidence on finasteride was ≥1% and greater than placebo over the 4 years of the study. In years 2-4 of the study, there was no significant difference between treatment groups in the incidences of impotence, decreased libido, and ejaculation disorder.

Year 1
(%)
Years 2, 3 and 4*
(%)
FinasteridePlaceboFinasteridePlacebo
    Impotence8.13.75.15.1
    Decreased
    Libido
6.43.42.62.6
    Decreased
    Volume of
    Ejaculate

3.7

0.8

1.5

0.5
    Ejaculation
    Disorder
0.80.10.20.1
    Breast
    Enlargement
0.50.11.81.1
    Breast
    Tenderness
0.40.10.70.3
    Rash0.50.20.50.1
N = 1524 and 1516, finasteride vs placebo, respectively
*Combined Years 2-4

Phase III Studies and 5-Year Open Extensions

The adverse experience profile in the 1-year, placebo-controlled, Phase III studies, the 5-year open extensions, and PLESS were similar.

Medical Therapy of Prostatic Symptoms (MTOPS) Study

In the MTOPS study, 3047 men with symptomatic BPH were randomized to receive finasteride 5 mg/day (n=768), doxazosin 4 or 8 mg/day (n=756), the combination of finasteride 5 mg/day and doxazosin 4 or 8 mg/day (n=786), or placebo (n=737) for 4 to 6 years.

The incidence rates of drug-related adverse experiences reported by ≥2% of patients in any treatment group in the MTOPS Study are listed in Table 2.

The individual adverse effects which occurred more frequently in the combination group compared to either drug alone were: asthenia, postural hypotension, peripheral edema, dizziness, decreased libido, rhinitis, abnormal ejaculation, impotence, and abnormal sexual function (see Table 2). Of these, the incidence of abnormal ejaculation in patients receiving combination therapy was comparable to the sum of the incidences of this adverse experience reported for the two monotherapies.

Combination therapy with finasteride and doxazosin was associated with no new clinical adverse experience.

Four patients in MTOPS reported the adverse experience of breast cancer. Three of these patients were on finasteride only and one was on combination therapy.

The MTOPS Study was not specifically designed to make statistical comparisons between groups for reported adverse experiences. In addition, direct comparisons of safety data between the MTOPS study and previous studies of the single agents may not be appropriate based upon differences in the patient population, dosage or dose regimen, and other procedural and study design elements.

Adverse ExperiencePlacebo

(N=737)
(%)
Doxazosin
4 mg or 8 mg*
(N=756)
(%)
Finasteride

(N=768)
(%)
Combination

(N=786)
(%)
  Body as a whole
        Asthenia7.115.75.316.8
        Headache2.34.12.02.3
  Cardiovascular
        Hypotension0.73.41.21.5
        Postural Hypotension8.016.79.117.8
  Metabolic and Nutritional
        Peripheral Edema0.92.61.33.3
  Nervous
        Dizziness8.117.77.423.2
        Libido Decreased5.77.010.011.6
        Somnolence1.53.71.73.1
  Respiratory
        Dyspnea0.72.10.71.9
        Rhinitis0.51.31.02.4
  Urogenital
        Abnormal Ejaculation2.34.57.214.1
        Gynecomastia0.71.12.21.5
        Impotence12.214.418.522.6
        Sexual Function Abnormal0.92.02.53.1
*Doxazosin dose was achieved by weekly titration (1 to 2 to 4 to 8 mg). The final tolerated dose (4 mg or 8 mg) was administered at end-Week 4. Only those patients tolerating at least 4 mg were kept on doxazosin. The majority of patients received the 8-mg dose over the duration of the study.

Long-Term Data

High-Grade Prostate Cancer

The PCPT trial was a 7-year randomized, double-blind, placebo-controlled trial that enrolled 18,882 men ≥55 years of age with a normal digital rectal examination and a PSA ≤3.0 ng/mL. Men received either finasteride (5 mg) or a placebo daily. Patients were evaluated annually with PSA and digital rectal exams. Biopsies were performed for elevated PSA, an abnormal digital rectal exam, or the end of the study. The incidence of Gleason score 8-10 prostate cancer was higher in men treated with finasteride (1.8%) than in those treated with placebo (1.1%). In a 4-year placebo-controlled clinical trial with another 5α-reductase inhibitor (dutasteride, AVODART), similar results for Gleason score 8-10 prostate cancer were observed (1% dutasteride vs 0.5% placebo).

No clinical benefit has been demonstrated in patients with prostate cancer treated with finasteride.

Breast Cancer

During the 4- to 6-year placebo- and comparator-controlled MTOPS study that enrolled 3047 men, there were 4 cases of breast cancer in men treated with finasteride but no cases in men not treated with finasteride. During the 4-year, placebo-controlled PLESS study that enrolled 3040 men, there were 2 cases of breast cancer in placebo-treated men but no cases in men treated with finasteride. During the 7-year placebo-controlled Prostate Cancer Prevention Trial (PCPT) that enrolled 18,882 men, there was 1 case of breast cancer in men treated with finasteride, and 1 case of breast cancer in men treated with placebo. The relationship between long-term use of finasteride and male breast neoplasia is currently unknown.

Sexual Function

There is no evidence of increased sexual adverse experiences with increased duration of treatment with PROSCAR. New reports of drug-related sexual adverse experiences decreased with the duration of therapy.

Post-marketing Experience

The following additional adverse events have been reported in postmarketing experience with finasteride. Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure:-hypersensitivity reactions, such as pruritus, urticaria, and angioedema (including swelling of the lips, tongue, throat, and face)-testicular pain-sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, decreased libido and ejaculation disorders (e.g. reduced ejaculate volume). These events were reported rarely in men taking finasteride for the treatment of BPH. Most men were older and were taking concomitant medications and/or had co-morbid conditions. The independent role of finasteride in these events is unknown.-male infertility and/or poor seminal quality were reported rarely in men taking finasteride for the treatment of BPH. Normalization or improvement of poor seminal quality has been reported after discontinuation of finasteride. The independent role of finasteride in these events is unknown.-depression-male breast cancer.

The following additional adverse event related to a sexual dysfunction that continued after discontinuation of treatment has been reported in postmarketing experience with finasteride at lower doses used to treat male pattern baldness. Because the event is reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate its frequency or establish a causal relationship to drug exposure:-orgasm disorders.

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