Fosamax vs Evenity (Romosozumab): Cost and Access Head-to-Head

What Are These Two Drugs and How Do They Work?

Alendronate and romosozumab attack bone loss through fundamentally different mechanisms. Alendronate suppresses osteoclasts, the cells that break bone down. Romosozumab inhibits sclerostin, a protein that normally puts a brake on bone formation, so it simultaneously increases bone building and decreases bone resorption. That dual action is why romosozumab can produce faster, larger gains in bone-mineral density (BMD) in a short window.

Alendronate: The Established Standard

Alendronate belongs to the bisphosphonate class and has been the dominant oral osteoporosis therapy since its FDA approval in 1995. Typical dosing is either 70 mg once weekly or 10 mg daily by mouth. It must be taken on an empty stomach with 8 oz of plain water, and the patient must remain upright for at least 30 minutes afterward to reduce esophageal irritation.

The drug incorporates into bone matrix and can remain active for years after discontinuation, which is why clinicians sometimes recommend a "drug holiday" after 3 to 5 years of therapy to weigh ongoing benefit against the rare risk of atypical femoral fracture. The FDA prescribing information for alendronate notes this risk and recommends periodic reassessment.

Romosozumab: The Bone-Building Agent

Romosozumab (brand name Evenity) is a humanized monoclonal antibody given as two 105 mg subcutaneous injections on the same day, once monthly, for exactly 12 months. After 12 doses the treatment course is complete. Patients are then typically transitioned to an antiresorptive agent such as alendronate or denosumab to preserve the BMD gains.

The FDA approval letter for romosozumab (March 2019) includes a Black Box Warning for increased risk of myocardial infarction (MI), stroke, and cardiovascular death. Romosozumab is contraindicated in patients who have had an MI or stroke within the preceding 12 months.

Fracture-Reduction Evidence: FIT vs ARCH

Both drugs have large randomized controlled trial data, but the trials differ in design, comparator, and the population studied. Comparing their efficacy numbers requires understanding those differences.

The FIT Trial (Alendronate vs Placebo)

The Fracture Intervention Trial (FIT), published in JAMA in 1998, enrolled 2,027 women with low femoral-neck BMD and randomized them to alendronate or placebo for 3 years. FIT demonstrated a 47% relative risk reduction in vertebral fractures with alendronate compared to placebo (relative risk 0.53, 95% CI 0.41 to 0.68). Hip fracture risk fell by 51% in the subgroup with pre-existing vertebral fractures.

The ARCH Trial (Romosozumab vs Alendronate)

The ARCH trial, published in the New England Journal of Medicine in 2017, enrolled 4,093 postmenopausal women with osteoporosis and at least one prior vertebral fracture. Participants received either romosozumab 210 mg monthly or alendronate 70 mg weekly for 12 months, followed by open-label alendronate in both groups. At 24 months, romosozumab-to-alendronate produced 48% fewer new vertebral fractures than alendronate-to-alendronate (relative risk 0.52, 95% CI 0.40 to 0.66, P<0.001). Clinical fracture risk was 20% lower and hip fracture risk was 38% lower in the romosozumab-first group.

The ARCH trial also reported more cardiovascular events in the romosozumab arm: 2.5% vs 1.9% with alendronate. That difference is the basis for the Black Box Warning.

What the Numbers Actually Mean

FIT and ARCH cannot be directly compared head-to-head because FIT used placebo as the comparator. ARCH, however, did use alendronate as an active comparator, making it the closest thing to a direct comparison available. The 48% additional vertebral fracture reduction in ARCH was measured on top of active alendronate therapy, which means romosozumab provides a measurable fracture-reduction advantage over alendronate in high-risk patients. The question for any given patient is whether that advantage justifies the cost, the injection burden, and the cardiovascular risk.

Cost Comparison: Alendronate vs Romosozumab

Cost is probably the single biggest practical difference between these two drugs.

Alendronate Pricing

Generic alendronate has been available in the United States since 2008. A 4-week supply of alendronate 70 mg (four tablets) costs approximately $10, $30 at most major retail pharmacies using a GoodRx or similar discount card. Even without insurance or discount programs, the out-of-pocket cost rarely exceeds $80 per month for the brand. Over a standard 3-year course, total drug cost for alendronate is roughly $360, $1,080 at generic prices.

The FDA's drug database lists over 20 approved generic alendronate products, which drives the commodity-level pricing.

Romosozumab Pricing

Romosozumab carries a list price of approximately $21,000, $23,000 per year, or about $1,750, $1,920 per monthly dose. With pharmacy and infusion fees, the actual cost per treatment course of 12 months can reach $25,000, $28,000 without insurance. The manufacturer, Amgen, offers a co-pay assistance program for commercially insured patients that can reduce out-of-pocket costs to as low as $5 per month, but that program excludes Medicare and Medicaid beneficiaries.

For Medicare Part D patients, romosozumab falls into a specialty tier. Under the Medicare Inflation Reduction Act's new $2,000 out-of-pocket cap (effective 2025), the annual patient exposure is capped, but the drug remains a high-cost specialty item that triggers utilization management.

Cost per Fracture Prevented

A 2019 cost-effectiveness analysis published in the Journal of Bone and Mineral Research modeled romosozumab followed by alendronate versus alendronate alone in a cohort of postmenopausal women aged 75 with a recent fracture. Romosozumab was cost-effective (incremental cost-effectiveness ratio below $100,000 per quality-adjusted life year) only in the highest-risk subgroup, specifically women aged 70 or older with a recent major fracture and T-score <-2.5. In lower-risk populations, alendronate was the cost-effective choice at any willingness-to-pay threshold modeled.

Insurance Access and Prior Authorization

Getting romosozumab approved through insurance is a multi-step process that alendronate simply does not require.

Alendronate Access

Alendronate is available at any retail pharmacy, requires no prior authorization under virtually any commercial or government insurance plan, and can be prescribed by any licensed prescriber. It is on the formulary preferred tier of every major Part D plan reviewed by CMS for 2024. Patients can also purchase it out-of-pocket at generic prices without involving insurance at all.

Romosozumab: Step Therapy Requirements

Nearly all major commercial payers and Part D plans require prior authorization (PA) for romosozumab. The typical PA criteria include:

• Diagnosis of postmenopausal osteoporosis with a T-score <-2.5 OR a fragility fracture
• Documentation of at least 12 months of bisphosphonate therapy (step therapy) OR documented intolerance or contraindication to bisphosphonates
• Cardiovascular risk screening (no MI or stroke in the prior 12 months)
• Prescribing by or in consultation with an endocrinologist, rheumatologist, or metabolic bone specialist at some plans

The step therapy requirement is not universal. The Endocrine Society's 2020 clinical practice guideline on osteoporosis states: "For patients at very high risk of fracture, we suggest anabolic therapy rather than oral bisphosphonates as initial treatment." That language gives clinicians the clinical justification needed to argue for PA approval without a bisphosphonate trial in truly high-risk cases, but insurance appeals still take time and administrative effort.

Specialty Pharmacy Dispensing

Romosozumab must be dispensed through a specialty pharmacy and is typically administered by a healthcare provider, adding scheduling and logistical barriers that do not exist for an oral generic tablet.

How to Choose: A Risk-Stratified Decision Framework

The right drug depends on fracture risk, cardiovascular history, patient preference, and payer access. The following framework aligns with the 2020 Endocrine Society guideline and the ARCH trial population characteristics.

Start With Alendronate If:

• FRAX 10-year major osteoporotic fracture risk is below 20%
• No recent major fragility fracture (within 24 months)
• T-score is between -2.5 and -3.0 without prior vertebral fracture
• Patient has a history of MI, stroke, or significant cardiovascular disease in the past 12 months
• Cost or access is a barrier and no manufacturer assistance is available
• Patient can tolerate oral dosing and upright positioning post-dose

Alendronate's 47-year safety record, generic availability, and oral route make it the right starting point for the majority of patients with postmenopausal osteoporosis.

Consider Romosozumab If:

• T-score is <-3.0 with at least one prior vertebral fracture
• Patient has experienced two or more fragility fractures despite oral bisphosphonate therapy
• FRAX 10-year hip fracture risk exceeds 4.5% (the threshold used in ARCH eligibility)
• Patient is intolerant of oral bisphosphonates (esophageal disease, inability to remain upright)
• Cardiovascular risk is low and no MI or stroke in the preceding 12 months
• Rapid BMD gain is needed (e.g., patient requires long-term glucocorticoid therapy)

The ARCH trial population had a mean T-score of -2.96 at the femoral neck and a high prevalence of prior vertebral fracture, giving a benchmark for the patient type where romosozumab showed its clearest advantage over alendronate.

Sequential Therapy Matters

Romosozumab's gains are not durable without follow-on antiresorptive therapy. In ARCH, the benefit of romosozumab was maintained because both arms transitioned to alendronate. Stopping all therapy after 12 months of romosozumab leads to rapid BMD loss. Patients and prescribers need a documented transition plan before starting romosozumab.

Safety Profiles: Key Differences

Alendronate Safety Concerns

Alendronate's most common adverse effects are upper gastrointestinal (GI): esophageal irritation, reflux, and dysphagia affect roughly 10 to 15% of users. Rare but serious risks include osteonecrosis of the jaw (ONJ) and atypical femoral fracture (AFF). A meta-analysis in the Annals of Internal Medicine found AFF incidence of approximately 3.2 to 50 cases per 100,000 person-years depending on duration of use, rising significantly after 5 or more years of continuous therapy.

Romosozumab Safety Concerns

Romosozumab carries the Black Box cardiovascular warning described above. In ARCH, the rate of serious cardiac adverse events was 2.5% in the romosozumab group vs 1.9% in the alendronate group over the first 12 months. Injection-site reactions occurred in about 5% of patients. ONJ and AFF have been reported in post-marketing data but appear less frequent than with long-term bisphosphonate use.

The FDA drug label for romosozumab states: "Romosozumab-aqqg is associated with an increased risk of MI, stroke, and cardiovascular death. Romosozumab-aqqg should not be initiated in patients who have had an MI or stroke within the preceding year."

Administration and Patient Burden

| Feature | Alendronate | Romosozumab | |---|---|---| | Route | Oral tablet | Subcutaneous injection (2 per visit) | | Frequency | Once weekly (or daily) | Once monthly | | Duration | 3 to 5 years typical | Exactly 12 months | | Administration site | Home | Clinic or specialty provider | | Morning fasting required | Yes (30 to 60 min) | No | | Upright posture post-dose | 30 min required | Not required | | Prescription type | Standard (any prescriber) | Often specialist-initiated | | Monitoring required | Renal function, calcium | Cardiovascular screen, calcium/vitamin D |

Patients who travel frequently, have swallowing difficulties, or cannot maintain the post-dose positioning requirements may actually find monthly injections easier to manage despite the clinic visit. Conversely, patients with needle phobia, transportation barriers, or poor venous access typically prefer the oral route.

The Role of Calcium and Vitamin D

Neither drug works optimally without adequate calcium and vitamin D. The National Institutes of Health Office of Dietary Supplements recommends 1,200 mg of calcium daily (from diet plus supplements) for women over 50 and 1,000 IU, 2,000 IU of vitamin D3 daily for patients on osteoporosis therapy. Hypocalcemia is a documented risk with romosozumab, and the manufacturer requires that calcium and vitamin D adequacy be confirmed before the first dose.

Switching Between Alendronate and Romosozumab

Switching from alendronate to romosozumab is clinically supported. The ARCH trial itself enrolled patients who had previously received bisphosphonates, and romosozumab still produced significant fracture reduction in that subgroup. The practical barrier is insurance step therapy documentation, not biology.

Switching from romosozumab back to alendronate is the expected clinical pathway after the 12-month treatment course. Data from ARCH confirm that transitioning to alendronate post-romosozumab preserves and modestly extends BMD gains compared to stopping all therapy.

A Cochrane systematic review of sequential osteoporosis therapy found that anabolic-first followed by antiresorptive therapy produced greater BMD gains at 24 months than antiresorptive-first strategies, which supports using romosozumab as an initial choice in very high-risk patients who can access it, then transitioning to alendronate.

Access Pathways and Practical Tips

For patients who need romosozumab but face insurance barriers, these specific steps improve approval rates:

1. Document fracture history with imaging reports and DXA scan results showing T-score <-2.5 or lower.
2. Provide a letter of medical necessity citing the ARCH trial and the Endocrine Society 2020 guideline language recommending anabolic-first therapy for very high-risk patients.
3. Record any bisphosphonate intolerance with a symptom diary or office visit note describing GI adverse effects.
4. Request cardiovascular clearance from cardiology if there is any ambiguity in the patient's cardiac history, as this documentation also helps the PA process.
5. Contact Amgen's Evenity patient support program (1-844-EVENITY) directly; the manufacturer's reimbursement specialists often know payer-specific PA pathways better than the prescribing office staff.

For alendronate, the primary access barrier is adherence, not cost or authorization. Roughly 50% of patients discontinue bisphosphonate therapy within 12 months of starting, according to a retrospective cohort analysis published in Osteoporosis International. Weekly dosing improves adherence over daily dosing, and automated refill programs at the pharmacy reduce the primary failure point.

Summary Data Table

| Attribute | Alendronate (Fosamax) | Romosozumab (Evenity) | |---|---|---| | Mechanism | Osteoclast inhibition | Sclerostin inhibition (dual: build + suppress) | | FDA approval | 1995 | March 2019 | | Key trial | FIT (N=2,027, JAMA 1998) | ARCH (N=4,093, NEJM 2017) | | Vertebral fracture RR reduction | 47% vs placebo | 48% vs alendronate at 24 months | | Monthly cost (no insurance) | $10, $30 (generic) | ~$2,100, $2,300 | | PA required | No | Yes (nearly all plans) | | Step therapy hurdle | None | Bisphosphonate trial usually required | | Black Box Warning | None | Cardiovascular (MI, stroke) | | Typical treatment duration | 3 to 5 years | 12 months (then transition) | | Generic available | Yes (since 2008) | No |