Summary Safety Review - Finasteride - Assessing the Potential Risk of Serious Muscle-Related Side Effects

June 22, 2017

Product

Finasteride (Propecia, Proscar and generic products)

Potential Safety Issue

Serious muscle-related side effects

Key Messages

  • Finasteride is a prescription drug that is authorized for sale in Canada to treat and control non-cancerous enlargement of the gland that makes semen in males (prostate gland) and, improves symptoms associated with this medical condition. At a lower dose, it is authorized for sale to treat hair loss in men.
  • Health Canada reviewed the risk of potential serious muscle-related side effects with finasteride use because of reports in which these side effects were seen in patients treated with Propecia and Proscar.
  • Health Canada’s review of the available information concluded that the risk of serious muscle-related side effects with the use of finasteride could not be ruled out. Currently, the product information for finasteride does not include the potential risk of serious muscle-related side effects. Health Canada has recommended that the manufacturers update the product information of finasteride-containing products to inform about this potential risk.

Overview

Health Canada reviewed the risk of potential serious muscle-related side effects with finasteride use because of reports in which these events were seen in patients treated with Propecia and Proscar. The safety review focussed on potential risks of serious muscle-related adverse events such as rhabdomyolysis (pain in muscles with breakdown of muscle tissue and an increase in certain muscle proteins known as creatine kinase [CK] enzymes, myopathy (disease of muscles with pain and an increase in CK enzymes) and muscle disorders such as pain, weakness, atrophy (wasting) or stiffness.

Use in Canada

  • Finasteride at a dose of 5mg is a prescription drug that is authorized for sale in Canada to treat and control non-cancerous enlargement of the prostate gland (benign prostatic hyperplasia) and improves symptoms related to this condition. Finasteride at a dose of 1mg is authorized for sale in Canada to treat hair loss in men (androgenic alopecia).
  • Finasteride (5mg) has been marketed in Canada since 1992 under the brand name Proscar, and finasteride (1mg) since 1998 under the brand name Propecia. Generic versions of finasteride are also available.

Safety Review Findings

  • At the time of this review, Health Canada had received 11 Canadian reports of serious muscle-related side effects suspected of being linked to finasteride use. Of these, 4 cases were further assessed:
    • One patient experienced myopathy while being treated for hair loss.
    • One patient with benign prostatic hyperplasia reported muscle pain (myalgia).
    • Two patients experienced weakness in muscles; one was using finasteride to treat hair loss but the indication is unknown for the fourth case.
  • Three of these patients recovered after stopping the use of finasteride (the outcome is unknown in the fourth case). In the remaining 7 reports, there was not enough information to establish a link between finasteride and muscle-related side effects.
  • Three additional cases of serious muscle-related side effects with the use of finasteride were reported in the literature. One case reporting myalgia was excluded from the review because other known factors may have caused the condition. The remaining 2 cases reported either myalgia with an increase in muscle enzymes, or rhabdomyolysis following the use of finasteride to treat hair loss in men. These patients recovered after stopping the use of finasteride.
  • The World Health Organization's Adverse Drug Reaction Database contained 508 reports of serious muscle-related side effects suspected of being linked to the use of finasteride, mostly atrophy, weakness, myalgia and sudden, strong muscle tightening (spasms). However, there was not enough information to conclude that finasteride caused muscle-related side effects.

Conclusions and Actions

  • Health Canada’s review of the available information concluded that the risk of serious muscle-related side effects with the use of finasteride could not be ruled out.
  • Currently, the product information for finasteride does not include the potential risk of serious muscle-related side effects. Health Canada has recommended that the manufacturers update the product information of finasteride-containing products to inform about this potential risk.
  • Health Canada encourages consumers and healthcare professionals to report any side effects related to the use of this health product.
  • Health Canada will continue to monitor safety information involving finasteride, as it does for all health products on the Canadian market, to identify and assess potential harms. Health Canada will take appropriate and timely action if and when any new health risks are identified.

Additional Information

The analysis that contributed to this safety review included scientific and medical literature, Canadian and international information and what is known about the use of this drug both in Canada and internationally.

For additional information, contact the Marketed Health Products Directorate.

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