For more information or confidential assistance
se habla español

Propecia and Erectile Dysfunction

Propecia erectile dysfunction patientOne of the brand name versions of finasteride marketed by Merck, Propecia is prescribed as a treatment for pattern baldness in men. Under the name Proscar, finasteride is also used, in an altered dose, as a treatment for enlarged prostates. The FDA approved Propecia for the U.S. market in 1997, subsequent to the drug showing positive results in generating and maintaining hair growth in a series of pre-market trials.

By the end of the last decade, Propecia had established itself as a top-selling drug, raking in some hundreds of millions of dollars for Merck annually.

However, critics of the medication suggest that the drug’s side effects label did not sufficiently warn users of the dangers, in particular the sort of sexual side effects that have recently been making headlines all over the United States. Merck’s warning claimed that only 2% of patients would experience some form of sexual dysfunction, and that the symptoms would disappear once the men stopped taking the drug.

Finasteride is a type II 5α-reductase inhibitor. It inhibits the body’s production of the enzyme responsible for converting testosterone to dihydrotestosterone. By disrupting the conversion, Propecia retards hair loss rates.

An increasing number of men have come forward to complain of adverse sexual side effects after taking Propecia, including weakened libido, erectile dysfunction, poor semen quality, difficulty reaching orgasm, and diminished semen volume. Many have reported permanent or long-lasting sexual problems that have continued for many months after ceasing treatment. Post-market studies have instigated Merck to emphasize the risk of Propecia-related impotence and other sexual dysfunctions on the label.

In addition to sexual impairment, men have accused Propecia of causing other problematic side effects, such as depression and memory difficulties.

ED (erectile dysfunction) refers to a man’s difficulty in maintaining an erection. It can be purely physiological, but may also be a result of emotional or psychological disorders.

Other factors may contribute to ED, including:

  • Taking SSRI antidepressants (Paxil, Zoloft, Prozac)
  • Anti-inflammatory medication
  • Smoking
  • Cardiovascular disease
  • Neurological syndromes
  • Hormonal imbalances
  • Stress and anxiety
  • Aging
  • Obesity
  • Diabetes
  • Renal damage or failure
  • Surgical complications 

Use of Propecia and the simultaneous occurrence of ED does not automatically prove a causal relationship, and doctors must first eliminate other potential causes before establishing any link.

The following diagnostic tests can determine if a psychological or physiological source is responsible for erectile dysfunction:

  • Snap gauge test (nocturnal penile tumescence test, or NPT), a ring made of plastic is placed around the penis each night before sleep. The ring will snap if an erection occurs. This tells the patient whether they are experiencing normal nocturnal erections (anywhere between 3 and 5 is considered the norm). If they are, a physiological cause – such as Propecia – can likely be discounted.
  • Rigiscan. Also a test of NPT, Rigiscan monitors the frequency and strength of a patient’s erections.
  • Magnetic resonance angiography (MRA) uses magnetic fields and radio waves to make scans of blood vessels in the penis. This can help doctors see whether they are functioning properly.
  • PBI (Penile Brachial Index). An ultrasound machine records the direction and speed of blood flow.
  • Bulbocavernosus reflex test. The doctor may conduct this manual test to determine whether erectile dysfunction is caused by poor nerve function. The penis head is squeezed to see how quickly the anus contracts in response.

Treatment for ED

Doctors have a number of effective, scientifically proven methods available for treating erectile dysfunction. The appropriate course of treatment will vary according to the underlying cause.

Treatments for ED (erectile dysfunction):

  • ·Counseling / Psychotherapy
  • ·Oral ED medications including Viagra, Cialis and Levitra
  • ·Penile injections or pellets
  • ·Penis pump: a vacuum-like device that manually draws blood to the penis
  • ·Elastic ring positioned at the penis’ base during an erection

Propecia Erectile Dysfunction

There have been a handful of studies indicating a link between Propecia and erectile dysfunction. The Swedish Medical Products Agency started to investigate reports of sexual side effects caused by the drug in 2006. Propecia-related impotence was found to have continued long after the patient discontinued taking it. The study prompted Merck to change the labeling in Sweden. No changes were made to the drug’s warning label in the U.S.

In the UK, a 2009 study showed that men reported impotence and other types of sexual impairment that persisted after they stopped taking the hair loss medication. In 2011, George Washington University (GWU) looked at 54 males who had taken Propecia. A range of side effects, including lowered libido and genital numbness, were reported by 86% of them. Out of the men who had experienced sexual problems, 96% of them continued to experience side effects a year or more following cessation of treatment.

The lead researcher at GWU, Dr. Michael Irwig, discovered that for the majority of patients experiencing some form of sexual dysfunction lasting three months or longer after they stopped using Propecia, “the sexual dysfunction continued for many months or years.”

Dr. Irwig went on to extrapolate that, “our findings make me suspicious that this drug may have done permanent damage to these men.”

FDA Demands Changes to Label Warning

In June 2011, Merck altered the drug’s label to reflect the possibility that some men may experience persistent erectile dysfunction after discontinuing their use of Propecia.

In 2012, the FDA mandated that Merck emphasize the risk of permanent sexual side effects on the label. The move came after the agency had collected over 400 reports of adverse sexual events between 1998 and 2011, all as a result of taking Propecia. Merck was also ordered to add other potential sexual side effects to the warning, including “orgasm disorders, ejaculation disorders, and libido disorders … [continuing] after discontinuation of the drug.”

Merck’s official response to the FDA’s demands stated: “Because these reactions 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.”

  1. WebMD,
  2. Wiley Online Library, Persistent Sexual Side Effects of Finasteride: Could They Be Permanent?
  3. Bloomberg, Merck’s Drug Linked to Sex Concerns After Use,
  4. National Institutes of Health, Persistent sexual side effects of finasteride for male pattern hair loss,