Addyi Geriatric (65+) Safety: What Older Women and Their Doctors Need to Know

What Is Flibanserin and Why Does Age Matter?

Flibanserin (brand name Addyi, Sprout Pharmaceuticals) is a non-hormonal, once-nightly oral tablet approved by the FDA in August 2015 for hypoactive sexual desire disorder (HSDD) in premenopausal women. It acts as a serotonin 1A receptor agonist and serotonin 2A receptor antagonist, with secondary dopamine D4 agonism, producing modest increases in satisfying sexual events (SSEs) versus placebo in phase 3 trials.

Age changes everything about how this drug behaves. Hepatic blood flow, renal glomerular filtration, and cytochrome P450 enzyme activity all decline with age, altering absorption, distribution, and elimination. A 65-year-old woman prescribed flibanserin may experience meaningfully higher peak plasma concentrations than a 35-year-old on the same 100 mg dose.

The Approved Indication Does Not Cover Postmenopausal or Geriatric Women

The FDA label specifies premenopausal women. Women aged 65 and older are almost universally postmenopausal, placing them outside the approved indication entirely. Any prescribing in this group is off-label, which shifts the burden of evidence onto the prescriber. The FDA Addyi prescribing information states: "Addyi is not indicated for use in postmenopausal women or in men." [1]

What the Phase 3 Trial Data Actually Showed

The BEGONIA trial (Journal of Sexual Medicine, 2014; N=949) tested flibanserin 100 mg nightly versus placebo over 24 weeks in premenopausal women. Flibanserin produced a mean increase of 0.5 to 1.0 additional SSEs per 28 days compared to placebo, a statistically significant but modest effect. [2] The mean participant age was approximately 36 years. Women aged 65 and older were not enrolled, so no efficacy or safety data in this demographic were generated by BEGONIA.

A pooled analysis of three phase 3 trials published in the Journal of Sexual Medicine confirmed similar modest SSE gains, with dizziness, somnolence, nausea, and fatigue as the most common adverse events, each occurring at rates two to three times higher than placebo. [3] All three trials excluded postmenopausal women.

FDA Black-Box Warning: Hypotension and Syncope

The FDA requires a Risk Evaluation and Mitigation Strategy (REMS) program for flibanserin because of a black-box warning for severe hypotension and syncope. [1] This risk is not theoretical. A pharmacokinetic interaction study showed that co-administration with alcohol produced mean maximum decreases in systolic blood pressure of 36 mmHg and diastolic blood pressure of 21 mmHg, with one subject reaching a systolic nadir of 70 mmHg. [4]

Why This Warning Hits Harder at Age 65 and Beyond

Blood pressure regulation becomes less reliable with age. Baroreceptor sensitivity decreases, and the autonomic nervous system's ability to compensate for positional changes diminishes. The prevalence of orthostatic hypotension in community-dwelling adults over 65 is approximately 20%, rising to over 30% in adults over 75, according to data reviewed by the American Heart Association. [5]

A woman already experiencing orthostatic hypotension who takes flibanserin at bedtime and rises to use the bathroom at night faces a compounded risk. CNS depression from flibanserin, baseline orthostatic instability, and a dark environment combine to make a fall highly probable in susceptible individuals.

Alcohol: An Absolute Contraindication That Becomes More Dangerous With Age

The REMS program prohibits alcohol consumption while taking flibanserin. Ethanol metabolism slows with age as alcohol dehydrogenase activity declines and body water composition decreases, producing higher blood alcohol concentrations per unit consumed in older women. [6] The combination of even a single standard drink with flibanserin poses greater hypotensive risk in a 68-year-old than in a 32-year-old on an equivalent dose. Prescribers should document a thorough alcohol use history before initiating therapy in any patient, and particularly in women over 65.

Drug-Drug Interactions in the Geriatric Polypharmacy Context

CYP3A4 Inhibitors Are Contraindicated

Flibanserin is primarily metabolized by CYP3A4, with minor contributions from CYP2C19. [1] Concomitant use of moderate or strong CYP3A4 inhibitors is contraindicated because it raises flibanserin plasma concentrations dramatically. Fluconazole, a moderate CYP3A4 inhibitor, increased flibanserin AUC by 7-fold in a drug-interaction study. [1] Diltiazem, a moderate inhibitor commonly used in older adults for rate control or hypertension, increased flibanserin AUC approximately 2-fold in the same dataset. [1]

Women aged 65 and older are far more likely to be taking these agents. A 2019 analysis in JAMA Internal Medicine found that 42% of adults over 65 take five or more prescription medications, and the prevalence of polypharmacy rises steeply with age. [7] Common geriatric medications that are moderate or strong CYP3A4 inhibitors include:

• Azole antifungals (fluconazole, itraconazole)
• Macrolide antibiotics (clarithromycin, erythromycin)
• Calcium channel blockers (diltiazem, verapamil)
• Certain HIV antiretrovirals
• Grapefruit juice in quantities common in older adults' diets

CYP2C19 Poor Metabolizers

Approximately 2 to 5% of the general population are CYP2C19 poor metabolizers, and certain ethnic groups have higher prevalence rates. [8] Several medications common in older adults, including omeprazole and fluoxetine, inhibit CYP2C19 and may raise flibanserin exposure above expected levels. The FDA label advises caution when CYP2C19 inhibitors are co-administered. [1]

CNS Depressants: Additive Risk

Flibanserin itself causes CNS depression. Benzodiazepines, Z-drugs (zolpidem, eszopiclone), opioids, first-generation antihistamines, and skeletal muscle relaxants each add to this burden. The 2023 American Geriatrics Society Beers Criteria explicitly recommends avoiding most CNS-active medications in older adults due to their association with cognitive impairment, sedation, and falls. [9] A clinician adding flibanserin to a regimen that already includes zolpidem and lorazepam creates three converging pathways to a fall.

Renal Function Decline and Pharmacokinetics in Older Women

How Aging Kidneys Change Drug Exposure

Renal function declines at a mean rate of approximately 0.75 to 1.0 mL/min/1.73 m² per year after age 40. [10] By age 70, a woman with no overt renal disease may have a GFR of 50 to 60 mL/min/1.73 m², placing her in the CKD stage G3a category without any clinical symptoms. This reduced clearance affects not only renally eliminated drugs but also drugs whose metabolites are renally excreted, potentially prolonging pharmacodynamic effects.

Flibanserin itself is primarily hepatically metabolized, with approximately 33% of metabolites excreted in urine. [1] The FDA label notes that flibanserin has not been studied in patients with renal impairment. [1] That data gap is relevant: if metabolite accumulation prolongs CNS effects in a patient with reduced GFR of 45 mL/min/1.73 m², no clinical trial has quantified that risk.

Hepatic Impairment: A Hard Contraindication

Flibanserin is contraindicated in patients with any degree of hepatic impairment. [1] Liver function may decline with age, and older women are more likely to have fatty liver disease, hepatic fibrosis from alcohol use, or drug-induced hepatotoxicity from other medications. Baseline liver function testing is warranted before prescribing in any older adult being considered for off-label use.

Falls and Fracture Risk: The Geriatric Safety Priority

Falls are the leading cause of injury-related death in adults aged 65 and older. The Centers for Disease Control and Prevention reports that approximately 36 million falls occur among older adults in the United States each year, resulting in over 32,000 deaths annually. [11] Hip fractures carry a one-year mortality rate of 20 to 30% in adults over 75. [12]

Any medication that causes hypotension, dizziness, or somnolence adds to falls risk in this population. Flibanserin does all three. In the phase 3 program, dizziness occurred in 11.4% of flibanserin-treated patients versus 2.2% of placebo patients, and somnolence occurred in 11.2% versus 3.2%. [3] Those rates were measured in women with a mean age of about 36. The absolute risk in a 70-year-old with reduced drug clearance, baseline orthostatic hypotension, and co-prescribed sleep aids is unknown but almost certainly higher.

The HealthRX clinical team uses the following decision framework when evaluating any off-label flibanserin request from a patient aged 65 or older:

1. Confirm postmenopausal status. If confirmed, the drug is off-label. Document that explicitly in the chart.
2. Screen the medication list. Any moderate or strong CYP3A4 inhibitor is a contraindication. Any CNS depressant is a compounding risk factor requiring individualized discussion.
3. Assess fall risk. Use the CDC STEADI algorithm or equivalent. A high STEADI score is a strong argument against prescribing.
4. Evaluate alcohol use. Use AUDIT-C. A score of 3 or higher in an older woman warrants extra caution or a decision not to prescribe.
5. Check liver function. Any hepatic impairment is an absolute contraindication.
6. Estimate GFR. A GFR <45 mL/min/1.73 m² warrants additional caution given absent renal-impairment data.
7. Document the benefit-risk conversation. Include the fact that no RCT data exist for this age group and that the drug is not FDA-indicated for postmenopausal women.
8. Set a 6-week reassessment. No improvement in SSEs at 6 weeks is a signal to discontinue.

The 2023 Beers Criteria and Broader Geriatric Prescribing Context

The American Geriatrics Society publishes the Beers Criteria as a guide to potentially inappropriate medication use in older adults. The 2023 update reinforces caution around CNS-active agents, drugs that increase orthostatic hypotension risk, and medications with narrow therapeutic indices in the context of age-related pharmacokinetic changes. [9] Flibanserin is not individually listed, but it meets multiple criteria that the document flags: CNS depression, hypotension risk, CYP3A4-mediated interaction burden, and absence of geriatric trial data.

The Endocrine Society's clinical practice guideline on female sexual dysfunction notes that HSDD treatment should begin with psychosocial interventions and that pharmacological options carry individual risk profiles requiring careful patient selection. [13] That guidance predates widespread geriatric flibanserin use but the principle applies directly.

Evaluating Benefit Against Risk in This Population

What "Modest Benefit" Means at the Population Level

The BEGONIA trial's primary endpoint, mean change in SSEs per 28 days, showed flibanserin producing approximately 0.5 to 1.0 additional SSEs per month over placebo in the study population. [2] That number represents a population mean. Some women reported meaningful benefit; others reported none. The number needed to treat (NNT) across the phase 3 program was calculated at approximately 10 to 14 for one additional SSE per month. [3]

For a 35-year-old premenopausal woman with no comorbidities and no interacting medications, an NNT of 10 to 14 may be an acceptable trade-off. For a 70-year-old on diltiazem, zolpidem, and omeprazole, the same NNT sits alongside drug interactions that raise exposure unpredictably, a falls risk that could be life-altering, and an off-label status that the FDA explicitly intended.

When to Discuss Alternatives

Non-pharmacological approaches to low sexual desire in older women include:

• Cognitive behavioral therapy (CBT) specifically targeting sexual function, which has evidence from randomized trials in postmenopausal women. [14]
• Mindfulness-based sex therapy, studied in peri- and postmenopausal women with HSDD. [15]
• Relationship counseling where partner dynamics contribute to reduced desire.
• Addressing genitourinary syndrome of menopause (GSM) with topical estrogen or ospemifene, since dyspareunia can suppress desire independently.

If local vaginal dryness, atrophy, or dyspareunia is the primary driver, treating GSM first with FDA-approved vaginal estrogen therapy may resolve the desire complaint without introducing a CNS-active drug. [16]

Deprescribing Flibanserin: When and How

Deprescribing is a structured, intentional reduction or cessation of a medication when the risks outweigh the benefits for that individual patient. For flibanserin in any patient, the FDA label itself states that discontinuation is appropriate if no improvement is seen in SSEs after 8 weeks of use at 100 mg nightly. [1]

For older adults, the reassessment window should be shorter. The HealthRX team recommends a 6-week review given the higher risk profile. If the patient reports no meaningful improvement in desire or SSEs, discontinue and document. If she reports benefit but has experienced dizziness, near-syncope, or a fall, the benefit-risk calculation has almost certainly shifted toward discontinuation.

Flibanserin has no described withdrawal syndrome, so abrupt discontinuation is appropriate and does not require tapering. [1]

Regulatory Status and REMS Program Requirements

The FDA approved flibanserin under a REMS program that requires prescribers to be certified. [1] The REMS requirements include:

• Counseling patients to avoid alcohol entirely during treatment.
• Counseling patients to avoid initiating flibanserin if they are taking moderate or strong CYP3A4 inhibitors or if they plan to start such a drug within 2 days.
• Educating patients about hypotension and syncope symptoms and what to do if they occur.

These requirements apply regardless of patient age. For an older adult, the prescriber should also document that the patient is outside the approved indication, that the off-label use has been explained, and that alternative treatments were discussed. That documentation protects both patient and provider.

The FDA MedWatch program allows clinicians and patients to report adverse events, including falls and syncope associated with flibanserin, at https://www.fda.gov/safety/medwatch. [17] Reporting geriatric adverse events contributes to the post-marketing safety signal for a drug that has essentially no pre-market geriatric data.

Monitoring Recommendations for Older Patients Who Proceed

For the rare clinical scenario where a prescriber and a geriatric patient reach a shared decision to trial flibanserin off-label, the following monitoring schedule is appropriate:

• Baseline: Complete medication reconciliation, liver function tests, CMP with GFR estimation, AUDIT-C alcohol screen, CDC STEADI fall risk assessment, and blood pressure measurement lying and standing.
• Week 2 follow-up: Phone or telehealth check-in for dizziness, orthostatic symptoms, somnolence, and any near-fall or fall events.
• Week 6 in-person or video visit: Reassess SSEs using a validated patient-reported outcome measure (e.g., FSEP-R or FSDS-R), repeat orthostatic blood pressure, review any new medications added since baseline.
• Week 8 decision point: Per FDA label guidance, discontinue if no meaningful SSE improvement is documented. [1]
• Every 6 months if continuing: Repeat full baseline workup including LFTs and GFR.

Orthostatic blood pressure measurement at every visit is low-cost and directly relevant to the primary safety concern. A drop of 20 mmHg systolic or 10 mmHg diastolic upon standing meets the clinical definition of orthostatic hypotension and should prompt immediate reassessment of whether flibanserin should continue. [5]