Addyi (Flibanserin) in Adults 65 and Older: What Geriatric Patients and Transitioning Adults Need to Know

What Is Flibanserin and Why Are Older Adults Asking About It?

Flibanserin works on the central nervous system rather than on peripheral vasculature. It acts as a serotonin 1A receptor agonist and serotonin 2A receptor antagonist, and it has dopamine D4 agonist activity. The net effect is a shift in the balance between inhibitory (serotonin) and excitatory (dopamine, norepinephrine) neurotransmission in regions that modulate sexual motivation. The FDA approved flibanserin in August 2015 under the brand name Addyi for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women.

The label explicitly names premenopausal women, but HSDD does not disappear at menopause. A 2019 analysis published in the Journal of Sexual Medicine found that HSDD prevalence in women aged 45 to 64 was approximately 8.9%, and rates in women 65 and older remain clinically significant in community samples. Women who were first prescribed Addyi in their late 40s or early 50s may now be in their late 60s or beyond, creating a real transition-of-care challenge. Their younger-adult prescribers may have retired or changed practice, their pharmacy networks may have shifted, and their physiology has changed in ways that affect how the drug behaves.

Why the Geriatric Population Was Underrepresented in Trials

The key trials that supported FDA approval, including the VIOLET, DAISY, and BEGONIA studies summarized in the FDA briefing document, enrolled predominantly premenopausal women with a mean age in the mid-30s to low-40s. The FDA's complete response review acknowledged the absence of adequate data in postmenopausal women and stated that efficacy and safety in that population have not been established.

That gap matters because aging changes nearly every pharmacokinetic parameter relevant to flibanserin: hepatic blood flow, plasma protein binding, body composition, and renal clearance all shift in ways that can raise drug exposure and extend the duration of adverse effects.

The Regulatory Picture for Off-Label Use in Older Adults

Prescribing flibanserin to a patient aged 65 or older is off-label. Off-label prescribing is legal and common, but it places a heavier documentation burden on the clinician. The prescriber must still complete REMS training, the dispensing pharmacy must be REMS-certified, and informed consent should explicitly address the fact that the drug has not been studied in this age group. The FDA's REMS document for Addyi outlines those requirements in full.

How Aging Alters Flibanserin Pharmacokinetics

Flibanserin is extensively metabolized by CYP3A4 with minor contribution from CYP2C19. It is highly protein-bound (98%) and has a half-life of approximately 11 hours under normal conditions. Each of those parameters shifts with age in predictable directions.

Hepatic Metabolism and Reduced First-Pass Effect

Hepatic blood flow declines roughly 40% between ages 25 and 75. A foundational review in Clinical Pharmacokinetics documented that age-related reductions in hepatic mass and perfusion reduce first-pass extraction for high-extraction drugs, raising peak plasma concentrations even when the dose is unchanged. Flibanserin has moderate-to-high hepatic extraction, so this effect is clinically meaningful. The FDA label already contraindicates flibanserin in patients with any degree of hepatic impairment. Many adults 65 and older have subclinical hepatic changes that do not meet a formal impairment diagnosis but still reduce metabolic capacity.

Plasma Protein Binding in Older Adults

Because flibanserin is 98% protein-bound, even small reductions in albumin concentration can meaningfully increase the free (active) fraction of the drug. Serum albumin declines with age, particularly in patients with chronic illness, poor nutritional status, or inflammation. A patient whose albumin drops from 4.2 g/dL to 3.4 g/dL may experience a clinically significant rise in free flibanserin without any change in dose.

CYP3A4 Interactions and Polypharmacy

Adults 65 and older take a median of five to six prescription medications. A study in the Journals of Gerontology found that 36% of older adults take at least one medication with a major drug-drug interaction potential. Flibanserin's CYP3A4 dependence makes it particularly vulnerable to this problem. Common geriatric medications that inhibit CYP3A4 include:

• Diltiazem and verapamil (cardiovascular)
• Fluconazole (antifungal)
• Clarithromycin (antibiotic)
• Several antiretroviral agents

The FDA label states that strong CYP3A4 inhibitors raise flibanserin area under the curve (AUC) by up to 7-fold, which is the basis for the contraindication. Moderate inhibitors require dose adjustments or avoidance. A full medication reconciliation is non-negotiable before prescribing or continuing flibanserin in any geriatric patient.

The Alcohol Interaction: Why It Is More Dangerous at 65

The black-box warning on flibanserin centers on the alcohol interaction. Even moderate alcohol consumption combined with flibanserin produces clinically significant hypotension and syncope. The FDA conducted a dedicated interaction study in which subjects who took flibanserin 100 mg with 0.4 to 0.8 g/kg alcohol had a substantially higher incidence of hypotension (symptomatic) and syncope compared with alcohol alone. Women appeared to be at greater risk than men in that study.

Why Older Adults Face Greater Consequences

Physiologic changes in adults 65 and older amplify the consequences of any hypotensive episode:

• Baroreceptor sensitivity declines, reducing the speed of compensatory heart-rate increase.
• Autonomic regulation of vascular tone is slower.
• Cerebral autoregulation is less efficient, so even brief blood-pressure drops can cause loss of consciousness.
• Osteoporosis means that a syncopal fall carries a much higher fracture risk.

The CDC reports that falls are the leading cause of injury death in adults 65 and older, with approximately 36,000 fall-related deaths recorded in 2020. A drug that raises syncope risk even modestly deserves special scrutiny in this group.

Practical Alcohol Counseling for Older Patients

Because alcohol consumption in older adults is often underreported, a structured screening tool such as the AUDIT-C is more useful than a single open-ended question. The USPSTF recommends screening for unhealthy alcohol use in adults 18 and older, including those in geriatric age ranges. If any regular alcohol use is identified, flibanserin is contraindicated regardless of how infrequent the drinking pattern appears to be.

Fall Risk and CNS Effects in Geriatric Patients

Sedation is among the most frequently reported adverse effects of flibanserin. In the key trials, somnolence occurred in approximately 11% of flibanserin-treated patients versus roughly 3% in the placebo group. The FDA's medical review also documented dizziness (11.4% vs. 2.9% placebo) and fatigue (9% vs. 5.5% placebo) as dose-dependent adverse effects.

Beers Criteria Considerations

The American Geriatrics Society Beers Criteria is the standard reference for medications that carry heightened risk in adults 65 and older. The 2023 update of the AGS Beers Criteria does not explicitly list flibanserin because the drug's labeled indication is premenopausal, but the criteria broadly flag CNS-active agents with sedative and hypotensive properties as potentially inappropriate in older adults. The Beers framework specifically cautions against drugs that increase fall and fracture risk, a category that flibanserin's adverse-effect profile would place it in on mechanistic grounds.

Timing of the Dose and Sleep Architecture

Flibanserin is dosed at bedtime precisely to reduce daytime somnolence. In younger adults, this largely mitigates the sedation problem. Older adults, however, have more fragmented sleep and are more likely to rise at night. A patient who takes flibanserin at 10 PM and wakes at 2 AM while significant drug concentrations remain may be at elevated fall risk during nighttime ambulation. Sleep architecture changes in aging are well-documented in a review in Nature and Science of Sleep, with older adults spending more time in lighter sleep stages and waking more frequently than younger cohorts.

Transition of Care: What Changes When a Patient Turns 65 or Changes Providers

"Transition of care" in this context describes two related scenarios: a patient who was on flibanserin before age 65 and is now in a geriatric or primary-care setting, and a patient who changes prescribers, insurance, or pharmacy while already on flibanserin. Both scenarios introduce real safety risks if REMS compliance lapses.

REMS Re-enrollment and Pharmacy Certification

The Addyi REMS requires that every prescribing clinician complete a training and enrollment process and that every dispensing pharmacy be certified. When a patient transitions from a gynecologist who is REMS-enrolled to an internist or geriatrician who is not, the prescription cannot legally be filled until the new prescriber completes enrollment. The FDA's REMS database confirms this requirement and provides the enrollment pathway.

In practice, this creates gaps. A patient who relocates to a new city, loses her OB-GYN, or transitions to a Medicare-focused primary care practice may find that her new prescriber is unfamiliar with REMS requirements for flibanserin. The prescriber either declines to enroll or unknowingly prescribes without enrollment, and the pharmacist at a non-certified pharmacy cannot dispense. The patient experiences an unplanned discontinuation, which, while not dangerous pharmacologically (there is no physical withdrawal syndrome documented for flibanserin), can be distressing.

Documenting the Transition

A proper transition-of-care note for a patient on flibanserin should include:

• Current dose and duration of use
• Documentation that the alcohol interaction has been counseled and that the patient abstains
• A current medication list screened for CYP3A4 inhibitors
• Liver function tests within the past 12 months
• An explicit discussion of the off-label status in patients 65 and older
• Confirmation that the receiving prescriber is REMS-enrolled or a plan to transfer to one who is

A 2022 JAMA Internal Medicine analysis of medication continuity during care transitions found that CNS-active medications were among those most frequently discontinued or dose-changed without documented clinical rationale during handoffs. Flibanserin, with its REMS overlay, may be even more vulnerable to unplanned discontinuation than typical CNS agents.

Insurance and Formulary Issues at 65

Medicare Part D does not cover flibanserin as of the 2025 formulary cycle. The drug's wholesale acquisition cost exceeds $800 per month for a 30-day supply at most retail pharmacies, placing it outside the budget of many patients on fixed incomes. When a patient turns 65 and transitions from employer-sponsored insurance to Medicare, she may lose coverage abruptly. Prescribers should address this financial transition proactively, ideally 3 to 6 months before the patient's 65th birthday.

Alternatives to Flibanserin for HSDD in Postmenopausal and Geriatric Women

Because flibanserin is not FDA-approved for postmenopausal women, several other evidence-based options deserve consideration.

Bremelanotide (Vyleesi)

Bremelanotide received FDA approval in 2019 for premenopausal HSDD. Like flibanserin, it is not approved for postmenopausal women. The key RECONNECT trials (N=1,247) demonstrated statistically significant improvements in desire and distress scores versus placebo. Adverse effects include nausea (40%), flushing, and transient blood-pressure elevation, which makes it potentially problematic in older adults with cardiovascular disease.

Systemic and Local Hormone Therapy

For postmenopausal women whose low desire is intertwined with genitourinary syndrome of menopause (GSM), estrogen therapy, either systemic or local vaginal, addresses contributing factors that flibanserin does not. The Menopause Society (formerly NAMS) 2022 position statement supports low-dose vaginal estrogen for GSM in postmenopausal women, including those with a history of breast cancer in selected cases.

Testosterone Off-Label

Off-label testosterone for postmenopausal HSDD has the broadest evidence base in this age group. A 2019 systematic review and meta-analysis in The Lancet Diabetes and Endocrinology (N=8,480 across 36 trials) found that testosterone therapy significantly improved sexual function scores versus placebo or comparator, with a standardized mean difference of 1.17 for satisfying sexual events. The authors concluded that testosterone is effective for postmenopausal HSDD, though no formulation is currently FDA-approved for this indication.

Psychotherapy and Sex Therapy

Pharmacologic treatment addresses one dimension of sexual desire. A Cochrane review of psychological interventions for sexual dysfunction in women found that cognitive behavioral therapy and mindfulness-based interventions produced significant improvements in desire and distress. Older adults who have experienced partner loss, body-image changes, or relationship transitions may find that non-pharmacologic approaches are as effective or more sustainable than medication alone.

Clinical Decision Checklist Before Continuing or Starting Flibanserin in a Patient 65 or Older

Prescribers considering flibanserin in a geriatric patient should work through each of the following before writing or renewing the prescription:

1. Confirm the diagnosis is acquired, generalized HSDD, not situational or relationship-based low desire.
2. Screen for alcohol use with AUDIT-C. Any positive screen is a contraindication.
3. Obtain a full medication list and check every agent against the CYP3A4 interaction table in the FDA label.
4. Review the most recent liver function panel. Any elevation in transaminases or evidence of hepatic disease is a contraindication.
5. Assess fall risk using the STEADI (Stopping Elderly Accidents, Deaths, and Injuries) algorithm. The CDC's STEADI toolkit provides validated screening tools for clinicians.
6. Confirm REMS enrollment for yourself and the dispensing pharmacy.
7. Document informed consent that includes the off-label nature of use in patients 65 and older.
8. Review the patient's insurance status to anticipate any coverage gap at age 65.
9. Schedule a follow-up visit at 4 weeks to assess for dizziness, somnolence, or blood-pressure changes.
10. Re-evaluate the benefit-risk balance at 8 weeks. If the patient has not experienced meaningful improvement in satisfying sexual events by 8 weeks on 100 mg nightly, discontinuation is appropriate per the FDA label guidance.

The AGS Beers Criteria methodology recommends that any CNS-active agent prescribed off-label to a geriatric patient be accompanied by a documented explicit benefit-risk discussion and a defined re-evaluation timeline. That standard applies directly here.

Monitoring Parameters After Starting Flibanserin in an Older Adult

Standard monitoring for younger adults on flibanserin focuses on symptom tracking and alcohol abstinence verification. For patients 65 and older, the monitoring protocol should be broader.

Blood Pressure and Orthostatic Measurements

Orthostatic blood pressure should be measured at baseline and at each follow-up for the first 3 months. A drop of 20 mmHg systolic or 10 mmHg diastolic on standing meets the clinical definition of orthostatic hypotension per American Heart Association criteria. Any patient meeting that threshold while on flibanserin warrants immediate reassessment of the benefit-risk balance.

Cognitive Assessments

CNS sedation from flibanserin may be subtle in older adults, presenting as mild cognitive slowing rather than obvious drowsiness. A brief baseline cognitive screen (Mini-Cog or MoCA) at initiation and at 8 weeks gives an objective comparison point. A 2021 review in Age and Ageing confirmed that sedating medications are a modifiable risk factor for cognitive impairment and dementia progression in older adults, strengthening the case for objective monitoring.

Liver Function Re-testing

Given the hepatic contraindication, liver function tests should be repeated annually or sooner if the patient develops any symptom of hepatic dysfunction, starts a new hepatotoxic medication, or gains significant weight.