Fosamax Legal and Patent Challenges

FDA Approval and Early Regulatory Milestones

The FDA approved alendronate sodium 10 mg daily tablets on September 29, 1995, under NDA 20-560, making it the first oral bisphosphonate cleared for treatment of postmenopausal osteoporosis in the United States. Merck had filed the application based on key trials showing statistically significant gains in lumbar-spine and hip bone mineral density (BMD) compared with placebo.

Within three years, the Fracture Intervention Trial (FIT) provided the fracture-reduction data that cemented alendronate's clinical position. The vertebral-fracture arm (N=2,027) demonstrated a 47% relative risk reduction in new vertebral fractures at 36 months among women with existing vertebral deformity [1]. FIT also showed a 51% reduction in hip fractures in the same population. Those numbers drove rapid adoption: by 2000, Fosamax held the majority of the U.S. osteoporosis prescription market.

The FDA broadened the approved indications several times. A 5 mg daily dose for osteoporosis prevention arrived in 1997. Approval for treatment of osteoporosis in men followed in 2000, and treatment of glucocorticoid-induced osteoporosis was added the same year. The weekly 70 mg tablet, approved in 2000 under NDA 21-575, became the dominant formulation because it improved adherence without sacrificing efficacy [2]. Each label expansion grew the prescribing population and, with it, Merck's commercial exposure to post-market safety signals.

Patent Strategy and Generic Entry

Merck's original composition-of-matter patent for alendronate sodium (U.S. Patent No. 4,621,077) was filed in 1986 and expired in 2008. A method-of-use patent covering once-weekly dosing (U.S. Patent No. 5,994,329) extended protection for the 70 mg tablet. Merck pursued additional patents on combination formulations, including alendronate plus cholecalciferol (Fosamax Plus D), which received FDA approval in 2005.

Generic manufacturers began filing Abbreviated New Drug Applications (ANDAs) with Paragraph IV certifications years before the 2008 expiry. Barr Pharmaceuticals (later acquired by Teva) was among the first filers. Merck litigated aggressively to defend the weekly-dosing patent, but settlements and the natural expiration timeline allowed generic alendronate sodium 70 mg tablets to reach U.S. pharmacies in February 2008.

The revenue impact was steep. Fosamax had generated roughly $3.2 billion in global sales in 2005. By 2009, generic erosion had reduced Merck's branded Fosamax revenue to under $500 million. The speed of the generic switch reflected both payer pressure and the bioequivalence simplicity of an oral solid-dosage bisphosphonate. Teva, Mylan, Sun Pharma, Apotex, and several other firms entered the market within the first year.

Merck attempted to slow substitution with the Fosamax Plus D combination tablet, arguing added vitamin D₃ (2,800 IU or 5,600 IU) provided a clinically distinct product. Generic alendronate-cholecalciferol combinations eventually reached the market as well, though Merck retained some brand loyalty among physicians who preferred the co-formulation. The overall patent arc of Fosamax is a textbook case study in branded-to-generic transition for a blockbuster specialty drug.

Osteonecrosis of the Jaw: The First Major Safety Signal

In 2003, oral surgeons began reporting cases of exposed, necrotic jawbone in patients receiving intravenous bisphosphonates for cancer-related skeletal events. Reports soon extended to oral bisphosphonates, including alendronate, taken for osteoporosis. The condition, termed bisphosphonate-related osteonecrosis of the jaw (BRONJ), posed a regulatory and legal challenge because the mechanism was poorly understood and the incidence was difficult to quantify.

The FDA responded in 2005 by requiring Merck to add jawbone osteonecrosis to the Fosamax label under Adverse Reactions. A 2007 position paper from the American Association of Oral and Maxillofacial Surgeons estimated the incidence of BRONJ with oral bisphosphonates at between 0.7 and 1 per 100,000 person-years of exposure [3]. That low incidence made individual causation difficult to establish in court, but hundreds of lawsuits were filed alleging that Merck had known about the risk before the label change and failed to warn.

A 2014 task force report from the American Association of Oral and Maxillofacial Surgeons updated the terminology to medication-related osteonecrosis of the jaw (MRONJ) to reflect that denosumab and antiangiogenic agents also carried the risk [4]. The broadened definition shifted the regulatory and scientific focus away from bisphosphonates alone. Most BRONJ/MRONJ personal-injury claims against Merck settled or were dismissed, but the signal had lasting consequences: dental screening before bisphosphonate initiation became standard clinical practice, and the label revision triggered by the litigation remains on every generic alendronate product insert today.

Atypical Femoral Fractures and the Multidistrict Litigation

A second, more commercially damaging safety signal emerged in the late 2000s. Case series from Singapore, New York, and Sweden described unusual subtrochanteric and diaphyseal femoral fractures occurring in patients on long-term bisphosphonate therapy. These atypical femoral fractures (AFFs) were characterized by a transverse fracture line, minimal trauma, cortical thickening, and prodromal thigh pain.

The 2010 task force report from the American Society for Bone and Mineral Research (ASBMR) formally defined the AFF case definition and noted a strong association with bisphosphonate duration exceeding 3 to 5 years [5]. The FDA issued a safety communication in October 2010 and required label changes for all bisphosphonates, including a new Warnings and Precautions section describing the risk.

Thousands of patients who had sustained subtrochanteric fractures while taking Fosamax filed lawsuits. The Judicial Panel on Multidistrict Litigation consolidated these claims into MDL No. 2243, assigned to Judge John F. Keenan in the Southern District of New York. By 2014, more than 4,000 cases were pending.

The bellwether trial strategy produced mixed results. In the first bellwether, Bernadette Glynn's case ended in a mistrial in 2013. A second bellwether brought by Plaintiff Lois Flemming resulted in a jury verdict for Merck in 2014. A third trial (Plaintiff: Shirley Boles) also went to Merck. The defense theme was consistent: Merck argued that the Fosamax label adequately warned of fracture risks and that the FDA had reviewed the AFF data and not required a contraindication.

Plaintiffs countered that Merck had data suggesting AFF risk as early as 2001 from the FIT Long-Term Extension (FLEX) study and internal pharmacovigilance databases, and that a stronger warning would have led prescribers to limit treatment duration. The litigation ultimately shaped how long-term bisphosphonate therapy is prescribed. Drug holidays after 3 to 5 years of oral bisphosphonate therapy, now recommended by the American Association of Clinical Endocrinology (AACE) [6], emerged partly from the clinical scrutiny catalyzed by the AFF lawsuits.

Merck v. Albrecht: The Supreme Court and Federal Preemption

The most consequential legal outcome from the Fosamax litigation was not a jury verdict but a procedural ruling. In Merck Sharp & Dohme Corp. v. Albrecht (No. 17-290), the Supreme Court addressed whether Merck could invoke federal preemption to block state failure-to-warn claims. The preemption defense rested on the argument that FDA regulations prevented Merck from unilaterally strengthening the Fosamax label, making it impossible to comply with both federal and state law.

The background: in 2008 and 2009, Merck had submitted a Changes Being Effected (CBE-0) supplement proposing to add AFF-related language to the Warnings section of the Fosamax label. The FDA rejected the proposed labeling change in 2009, stating that a causal link between bisphosphonates and stress fractures was not established at that time [7]. Merck argued that this rejection proved the FDA would have blocked any stronger warning, and that state-law claims demanding such a warning were therefore preempted.

On May 20, 2019, the Supreme Court ruled 6-3 that preemption is a question of law for judges, not juries. The Court remanded the case, instructing the Third Circuit to evaluate, using the "clear evidence" standard from Wyeth v. Levine, whether the FDA would have rejected the specific labeling change that plaintiffs alleged should have been made [8]. The ruling did not end the litigation outright, but it gave Merck a procedural framework for arguing preemption on a case-by-case basis. Lower courts have since applied Albrecht in bisphosphonate and non-bisphosphonate failure-to-warn cases.

The case is studied in pharmaceutical regulatory law because it sits at the intersection of the FDA's CBE supplement process, branded-drug manufacturer duties, and the limits of Hatch-Waxman-era tort liability. For prescribers, the practical implication is blunt: the label that exists at any given moment may not reflect the full risk profile of the drug, and litigation often drives label changes years before the FDA mandates them.

Label Evolution: A Timeline of Safety Updates

The Fosamax prescribing information has been revised more than a dozen times since 1995. Key label milestones include:

1996-1999: Upper GI adverse reactions (esophagitis, esophageal ulcers, esophageal erosions) added to Warnings. Dosing instructions updated to require upright posture for at least 30 minutes after administration and intake with a full glass of plain water.

2003-2005: Musculoskeletal pain (severe, incapacitating) added to Post-Marketing Experience. Osteonecrosis of the jaw added to Adverse Reactions.

2008: Merck submits CBE-0 supplement proposing femoral shaft fracture warning; FDA rejects the proposed language.

2010: FDA mandates bisphosphonate-class label revision adding atypical subtrochanteric and diaphyseal femoral fractures to Warnings and Precautions. Merck updates the Fosamax label accordingly.

2011: Esophageal cancer reports added to Adverse Reactions following FDA review of post-marketing data and epidemiologic studies [9]. The label notes that a causal relationship has not been established.

2012-present: Hypocalcemia warnings strengthened. Renal impairment guidance updated to recommend against use in patients with creatinine clearance <35 mL/min.

Each label change carried downstream effects for generic alendronate products. Under FDA regulations, ANDA holders must update their labeling to match the reference listed drug (RLD) label. Generic manufacturers therefore inherited every safety warning added to Fosamax without having the ability to independently modify their labels through the CBE supplement pathway. This asymmetry is central to the ongoing legal debate about generic-drug preemption under PLIVA v. Mensing (2011) and Mutual Pharmaceutical v. Bartlett (2013).

Post-Market Surveillance and FDA Sentinel

The FDA has used Fosamax/alendronate as a case study for its Sentinel System, the active post-market surveillance program that mines electronic health data from over 100 million patients. A Sentinel-based analysis published in 2020 evaluated the association between oral bisphosphonate use and atypical femoral fractures using claims data from multiple health plans [10]. The study confirmed a duration-dependent increase in AFF risk, with the highest rates in patients using bisphosphonates for more than 5 years.

This type of real-world evidence generation represents the modern regulatory complement to randomized controlled trials. For alendronate, the Sentinel data reinforced what the clinical literature and the litigation had already suggested: bisphosphonate therapy has a therapeutic window, and risk-benefit assessment must account for cumulative exposure.

The FDA's 2022 Drug Safety Communication on bisphosphonates reiterated that the benefits of fracture reduction outweigh the risks of AFF and ONJ for most patients with osteoporosis, particularly in the first 3 to 5 years of therapy [7]. The agency did not impose new restrictions but encouraged shared decision-making about treatment duration.

Implications for Current Prescribing

The legal and regulatory history of alendronate has directly shaped three clinical practices that physicians follow today.

First, bisphosphonate drug holidays are now standard. The AACE/ACE 2020 clinical practice guidelines recommend reassessing fracture risk after 5 years of oral bisphosphonate therapy (or 3 years of intravenous zoledronic acid) and considering a temporary discontinuation in patients who are no longer at high fracture risk [6]. The AFF litigation accelerated adoption of this practice by years.

Second, dental evaluation before initiating bisphosphonate therapy is routine. The American Dental Association and the ASBMR both recommend completing invasive dental procedures before starting an oral bisphosphonate, and the ONJ risk disclosure is a standard part of informed consent.

Third, the generic alendronate preemption question remains unresolved. Patients injured by generic drugs face a narrower path to litigation than those injured by brand-name products. The PLIVA v. Mensing decision effectively immunized generic manufacturers from state failure-to-warn claims, creating a system where the most commonly prescribed form of the drug carries the fewest legal accountability mechanisms.

Alendronate remains on the WHO Model List of Essential Medicines and is a first-line agent for osteoporosis in every major guideline [11]. Its regulatory file, now spanning three decades, contains more post-approval safety supplements, litigation records, and label revisions than almost any other osteoporosis therapy. Clinicians prescribing alendronate in 2026 should verify that patients understand the current label warnings, particularly regarding treatment duration, jaw health, and the prodromal thigh pain that may signal an atypical fracture.