Flibanserin (Addyi), a Viagra-like drug, has been approved by the Food and Drug Administration (FDA) for the treatment of female sexual interest/arousal disorder (FSIAD) in premenopausal women.

FSIAD is also known as hypoactive sexual desire disorder (HSDD).

Currently, Addyi is only available through certain prescribers and pharmacies. It’s prescribed by approved providers in agreement between the manufacturer and the FDA. A prescriber must be certified by the manufacturer to meet certain FDA requirements.

It’s taken once per day, at bedtime.

The FDA hasn’t approved Viagra (sildenafil) itself for women to use. However, it has been prescribed off-label for women with a low sex drive.

OFF-LABEL DRUG USE Off-label drug use means a drug that’s approved by the FDA for one purpose is used for a different purpose that hasn’t yet been approved. However, a doctor can still use the drug for that purpose. This is because the FDA regulates the testing and approval of drugs, but not how doctors use drugs to treat their patients. So, your doctor can prescribe a drug however they think is best for your care.

Evidence of its effectiveness is mixed at best. A review of trials of Viagra in women speculates that positive results are observed in regard to physical arousal. However, this isn’t the case for the more complex nature of FSIAD.

For example, the review detailed a study that gave Viagra to 202 postmenopausal women with primary FSIAD.

Researchers observed an increased amount of arousal sensations, vaginal lubrication, and orgasm in study participants. However, women with secondary FSIAD-associated disorders (such as multiple sclerosis (MS) and diabetes) reported no increase in desire or enjoyment.

A second study discussed in the review found that both premenopausal and postmenopausal women reported no significant positive responses when using Viagra.

There are several reasons that women would seek out a Viagra-like pill. As they approach middle age and beyond, it’s not uncommon for women to observe a decrease in their overall sex drive.

A decrease in sex drive can also originate from daily stressors, significant life events, or chronic conditions such as MS or diabetes.

However, some women observe a decrease or absence in sex drive due to FSIAD. According to one expert panel and review, FSIAD is estimated to affect about 10 percent of adult women.

It’s characterized by the following symptoms:

Flibanserin was originally developed as an antidepressant, but it was approved by the FDA for treatment of FSIAD in 2015.

Its mode of action as far as it relates to FSIAD isn’t well-understood. It’s known that taking flibanserin regularly raises levels of dopamine and norepinephrine in the body. At the same time, it lowers levels of serotonin.

Both dopamine and norepinephrine are important for sexual excitement. Dopamine has a role in boosting sexual desire. Norepinephrine has a role in promoting sexual arousal.

The FDA approval of flibanserin was based off the results of three phase III clinical trials. Each trial lasted 24 weeks and evaluated the efficacy of flibanserin compared to a placebo in premenopausal women.

The investigators and the FDA analyzed the results of the three trials. When adjusted for placebo response, about 10 percent of participants reported a “much improved” or “very much improved” status in trial weeks 8 to 24. This is a modest improvement when compared to Viagra.

A review published three years after Viagra’s FDA approval for treating erectile dysfunction (ED) summarizes the worldwide responses to treatment. In the United States, for example, 74 percent of participants responded positively. This is compared to a 19 percent positive response for those taking a placebo.

In postmenopausal women

Flibanserin isn’t FDA-approved for use in postmenopausal women. However, the efficacy of flibanserin in this population was assessed in a single trial.

The results were reported as similar to those reported in premenopausal women. This will need to be replicated in additional trials for it to be approved for postmenopausal women.

The most common side effects of flibanserin include:

FDA warnings: On liver disease, enzyme inhibitors, and alcohol

  • This drug has boxed warnings. These are the most serious warnings from the Food and Drug Administration (FDA). A boxed warning alerts doctors and patients about drug effects that may be dangerous.
  • Flibanserin (Addyi) can cause fainting or severe hypotension when taken by people with liver disease or alongside certain drugs, including alcohol.
  • You shouldn’t use Addyi if you take certain moderate or strong CYP3A4 inhibitors. This group of enzyme inhibitors includes select antibiotics, antifungals, and HIV medications, as well as other types of drugs. Grapefruit juice is also a moderate CYP3A4 inhibitor.
  • To prevent these side effects, you should also refrain from drinking alcohol for at least two hours before taking your nightly dose of Addyi. After you take your dose, you should refrain from drinking alcohol until the next morning. If you’ve consumed alcohol less than two hours before your anticipated bedtime, you should skip that night’s dose instead.

Flibanserin shouldn’t be used in people with liver problems.

Talk to your doctor about what medications and supplements you’re taking before beginning flibanserin. You also shouldn’t take flibanserin if you’re taking any of the following medications or supplements:

  • certain medications used to treat cardiovascular conditions, such as diltiazem (Cardizem CD) and verapamil (Verelan)
  • certain antibiotics, such as ciprofloxacin (Cipro) and erythromycin (Ery-Tab)
  • medications to treat fungal infections, such as fluconazole (Diflucan) and itraconazole (Sporanox)
  • HIV medications, such as ritonavir (Norvir) and indinavir (Crixivan)
  • nefazodone, an antidepressant
  • supplements such as St. John’s wort

Many of these drugs belong to a group of enzyme inhibitors known as CYP3A4 inhibitors.

Lastly, you shouldn’t drink grapefruit juice while taking flibanserin. It’s also a CYP3A4 inhibitor.

Addyi and alcohol

When Addyi was first FDA-approved, the FDA warned those using the drug to abstain from alcohol due to the risk of fainting and severe hypotension. However, the FDA updated its warning on alcohol in April 2019.

If you’re prescribed Addyi, you no longer have to avoid alcohol completely. However, after you take your nightly dose, you should refrain from drinking alcohol until the next morning.

You should also refrain from drinking alcohol for at least two hours before taking your nightly dose. If you’ve consumed alcohol less than two hours before your anticipated bedtime, you should skip that night’s dose of Addyi instead.

If you miss a dose of Addyi for any reason, don’t take a dose to make up for it the next morning. Wait until the next evening and resume your regular dosing schedule.

Flibanserin had a challenging path to FDA approval.

The FDA reviewed the drug three times before approving it. There were concerns about its efficacy when compared with negative side effects. These concerns were the main reasons why the FDA recommended against approval after the first two reviews.

There were also lingering questions regarding how female sexual dysfunction should be treated. Sex drive is quite complex. There’s both a physical and a psychological component.

Flibanserin and sildenafil work in different ways. Sildenafil, for example, doesn’t increase sexual arousal in men. On the other hand, flibanserin works to raise levels of dopamine and norepinephrine to promote desire and arousal.

Thus, one pill targets a physical aspect of sexual dysfunction. The other targets the feelings of arousal and desire, a more complicated issue.

Following a third review, the FDA approved the drug due to unmet medical needs. However, concerns still remained regarding side effects. A particular concern is severe hypotension observed when flibanserin is taken with alcohol.

There are many causes of low sex drive, ranging from everyday stressors to FSIAD.

Viagra has seen mixed results in women in general, and it hasn’t been found effective for women with FSIAD. Premenopausal women with FSIAD may see a modest improvement in desire and arousal after taking Addyi.

Talk to your doctor if you’re interested in taking Addyi. Also be sure to discuss your other medications or supplements with your doctor before using Addyi.