Bisphosphonate Holiday Protocols: When to Stop, How Long to Pause, and What to Do Next

What Is a Bisphosphonate Holiday and Why Does It Exist?

A bisphosphonate holiday is a deliberate, time-limited pause in bisphosphonate therapy taken after an adequate initial treatment course. Because bisphosphonates bind tightly to hydroxyapatite and suppress osteoclast activity for months to years after the last dose, bone mineral density (BMD) often remains stable during a well-planned pause. The holiday concept addresses two rare but serious complications that accumulate with prolonged exposure: atypical femoral fractures (AFF) and osteonecrosis of the jaw (ONJ).

The American Society for Bone and Mineral Research (ASBMR) Task Force 2014 report estimated the AFF incidence at roughly 3.2 to 50 cases per 100,000 person-years with short-term use, rising to as high as 113 per 100,000 person-years after more than 8 years of treatment [1]. That absolute risk remains small, but because AFF causes complete femoral shaft fracture with minimal trauma and can be bilateral, clinicians weigh it seriously against continued suppression of osteoclast activity. ONJ risk, while more commonly associated with high-dose intravenous bisphosphonates used in oncology, also accumulates over time in the osteoporosis setting [2].

The holiday does not mean stopping calcium, vitamin D, or lifestyle measures. Those continue throughout the pause without interruption.

Who Qualifies for a Bisphosphonate Holiday?

Not every patient is a candidate. Patient selection determines whether a holiday is safe or a setup for a fracture.

The American Association of Clinical Endocrinology (AACE) 2020 clinical practice guidelines state: "For patients at moderate risk for fracture (T-score between -2.0 and -2.5, no prior major osteoporotic fracture, and low FRAX score), a drug holiday after 3 to 5 years of oral bisphosphonate therapy or 3 years of intravenous zoledronic acid is reasonable" [3]. Patients at high or very high fracture risk, defined as T-score <-2.5, prior hip or vertebral fracture, or 10-year FRAX major osteoporotic fracture probability above 20%, should generally not take a holiday or should be transitioned to an alternative agent rather than simply stopping.

Practical selection criteria include the following:

Candidates for a holiday:

• T-score at hip or spine better than -2.5 after the initial course
• No hip or vertebral fracture during initial therapy
• 10-year FRAX hip fracture probability <3% at reassessment
• Stable BMD on serial DXA (less than 5% loss per year over the last two scans)

Patients who should continue or switch agents:

• Prior hip or vertebral fracture
• T-score <-2.5 at any major site despite treatment
• High glucocorticoid use (prednisone 7.5 mg/day or more for 3 or more months)
• Confirmed radiographic AFF prodromal changes (cortical thickening, beaking, or stress reaction on femur X-ray)

Evidence Base: What the Long-Term Trials Show

The FLEX Trial (Alendronate)

The FLEX trial is the cornerstone study for oral bisphosphonate holiday decisions. In FLEX, 1,099 postmenopausal women who had completed 5 years of alendronate were randomized to continue alendronate for 5 more years or switch to placebo. After 5 additional years, the placebo group showed modest BMD decline (about 3% at the total hip) but no statistically significant increase in nonvertebral fracture risk compared to the continuation group [4]. However, in the prespecified subgroup analysis, women with femoral neck T-score <-2.5 at the end of the initial 5-year course had significantly more clinical vertebral fractures during the holiday (P<0.05) [4]. This subgroup finding drives current guidance that higher-risk patients should not pause.

The HORIZON-PFT Extension (Zoledronic Acid)

In the HORIZON-Key Fracture Trial extension, 1,233 women who had completed 3 annual infusions of zoledronic acid 5 mg were randomized to 3 more infusions or placebo for 3 more years. Morphometric vertebral fracture risk was significantly lower in the 6-year group than the 3-year group (relative risk reduction 52%), but hip fracture rates did not differ significantly [5]. The investigators concluded that patients at higher fracture risk benefit from continuing to 6 years, while lower-risk patients can stop after 3 infusions. Bone turnover markers remained suppressed for 12 to 24 months after the last zoledronic acid infusion, providing a built-in pharmacokinetic buffer during the early holiday period.

Risedronate Duration Data

Risedronate dissociates from bone faster than alendronate, which means BMD may decline more quickly after stopping. A post-hoc analysis of the VERT trials found that fracture protection waned within 1 year of discontinuation in some higher-risk patients [6]. Clinicians often allow a 2-year holiday for risedronate compared to 3 to 5 years for alendronate, and monitoring frequency should be increased to annual DXA rather than every 2 years.

Holiday Duration and Monitoring Schedule

The duration of a bisphosphonate holiday is not one-size-fits-all. The table below summarizes recommended maximum pause durations by agent and risk tier based on AACE 2020 and ASBMR 2022 position statements.

| Agent | Initial Course | Holiday Duration (Low Risk) | Holiday Duration (Moderate Risk) | |---|---|---|---| | Alendronate 70 mg/week | 5 years | 3 to 5 years | 2 to 3 years | | Risedronate 35 mg/week | 3 to 5 years | 1 to 2 years | 1 year | | Ibandronate 150 mg/month | 3 to 5 years | 1 to 2 years | Not routinely recommended | | Zoledronic acid 5 mg/year | 3 infusions | 3 years | 1 to 2 years |

Monitoring during the holiday:

1. DXA at baseline (holiday entry), then every 2 years (annual for risedronate)
2. Fasting urine N-telopeptide (NTX) or serum CTX at 12 to 18 months. A rise above the premenopausal reference range suggests rapid bone loss and should prompt reassessment
3. FRAX recalculation at each DXA visit using current T-score and updated clinical risk factors
4. Lateral spine X-ray or VFA (vertebral fracture assessment) if height loss exceeds 2 cm or new back pain develops

Restart therapy without waiting for the next scheduled visit if the patient sustains any fragility fracture during the holiday.

Denosumab Is Not a Bisphosphonate: Holiday Rules Do Not Apply

Denosumab (Prolia), dosed at 60 mg subcutaneously every 6 months, works through a fundamentally different mechanism. It is a fully human monoclonal antibody that inhibits RANKL. Unlike bisphosphonates, denosumab does not incorporate into bone mineral matrix, so its anti-resorptive effect disappears within 6 to 9 months of the last injection [7].

Stopping denosumab without a transition plan carries a real risk of rebound hypercalcemia and multiple vertebral fractures. The European Calcified Tissue Society (ECTS) issued a position statement in 2017 noting that post-denosumab vertebral fracture clusters involved a median of 3 vertebrae per patient and often occurred within 8 to 16 months of the last injection [8]. The ASBMR Task Force wrote: "Patients should be counseled that discontinuing denosumab without subsequent antiresorptive therapy may result in rapid bone loss and increased vertebral fracture risk" [7].

Standard denosumab transition protocol:

• Complete the planned denosumab course (typically 5 to 10 years)
• Administer one infusion of zoledronic acid 5 mg approximately 6 months after the last denosumab injection
• Check bone turnover markers (CTX) at 9 to 12 months post-zoledronate; if CTX is still elevated, consider a second infusion
• Some clinicians prefer 2 to 3 years of oral alendronate if IV access is limited or the patient prefers oral dosing, though evidence for this approach is less strong than for zoledronic acid

The denosumab q6-month schedule must therefore be maintained without gaps unless a bridging agent is immediately available. Missing a dose by more than 4 to 6 weeks should prompt urgent consultation to arrange bridging therapy.

Vitamin D Repletion During a Bisphosphonate Holiday

Vitamin D status is non-negotiable during both active bisphosphonate therapy and any holiday period. Bisphosphonates have essentially no anti-fracture efficacy in the setting of severe vitamin D deficiency, because secondary hyperparathyroidism drives osteoclast activity independently of the drug's mechanism [9].

The Endocrine Society's clinical practice guideline recommends maintaining serum 25-hydroxyvitamin D (25(OH)D) at 40 to 60 ng/mL in patients treated for osteoporosis, with a minimum floor of 30 ng/mL [10]. Most adults require 1,500 to 2 to 000 IU of vitamin D3 daily to sustain that target, though obese individuals (BMI above 30), patients with malabsorption syndromes, and those on enzyme-inducing anticonvulsants may need 6,000 to 10 to 000 IU daily to achieve the same serum level [10].

Repletion dosing for deficient patients (25(OH)D <20 ng/mL):

• High-dose loading: 50 to 000 IU ergocalciferol (D2) or cholecalciferol (D3) once weekly for 8 to 12 weeks, followed by re-testing
• Maintenance after repletion: 2 to 000 IU cholecalciferol daily, adjusted by repeat serum level at 3 months
• Patients with fat malabsorption (celiac, Crohn's, bariatric surgery): consider 50 to 000 IU two to three times weekly as ongoing maintenance, with quarterly monitoring

Concurrent calcium intake targets 1 to 200 mg per day total from all sources in women over 50 and men over 70 [3]. Supplemental calcium should make up the difference if dietary intake is estimated at less than 800 mg per day. Calcium carbonate requires gastric acid for optimal absorption and should be taken with food; calcium citrate is absorbed independently of meal timing and is preferred in patients on proton pump inhibitors [3].

Vitamin K2 (menaquinone-7, MK-7) is sometimes discussed alongside vitamin D for its putative role in directing calcium toward bone matrix via carboxylation of osteocalcin and matrix Gla protein. A 2019 3-year randomized controlled trial (N=244) in postmenopausal women found that 180 mcg/day of MK-7 reduced femoral neck bone loss compared to placebo (P<0.05), though the absolute effect on BMD was modest and fracture outcomes were not measured [11]. Current AACE guidelines do not list MK-7 as a recommended adjunct, but its safety profile at nutritional doses is well established. Clinicians may discuss it with patients interested in additional dietary adjuncts.

Managing the Return to Therapy After a Holiday

Deciding when and how to restart bisphosphonates requires the same clinical framework used for initial prescribing. The triggers for restart are:

1. T-score decline to <-2.5 on holiday DXA
2. Incident fragility fracture at any site
3. FRAX major osteoporotic fracture probability rising above 20% (or hip above 3%) due to new risk factors (new glucocorticoid use, weight loss exceeding 10%, new vertebral fracture on VFA)
4. CTX or NTX rising above the premenopausal range at the 12 to 18-month marker check

When restarting, clinicians may continue the same bisphosphonate or switch agents based on updated fracture risk. Patients who experienced an incident hip or vertebral fracture during the holiday meet AACE criteria for "very high" fracture risk and should be considered for anabolic agents (teriparatide, abaloparatide, or romosozumab) rather than returning to bisphosphonate therapy alone [3].

The FREEDOM Extension trial demonstrated that up to 10 years of denosumab therapy was associated with continuous BMD gains without a plateau, which has led some guidelines to extend denosumab treatment beyond the 5-year mark in high-risk patients rather than stopping and bridging [12]. This contrasts with bisphosphonate holidays and reinforces why the two drug classes require entirely separate decision frameworks.

Special Populations and Edge Cases

Glucocorticoid-induced osteoporosis (GIOP): Patients on chronic systemic glucocorticoids lose bone rapidly through RANKL upregulation and osteoblast suppression. The American College of Rheumatology (ACR) 2022 GIOP guideline recommends continuing bisphosphonates for the duration of glucocorticoid therapy at medium or high risk, with no defined holiday period while the steroid continues [13]. A holiday becomes feasible only after tapering to the lowest effective glucocorticoid dose.

Premenopausal women: Bisphosphonate holidays in premenopausal women are rarely relevant outside glucocorticoid-induced osteoporosis or secondary causes. The long skeletal half-life of alendronate raises theoretical concerns about fetal skeletal development, so all premenopausal women on bisphosphonates who are considering pregnancy should discuss timing with their physician. Current evidence is insufficient to define a safe washout interval, but animal data suggest fetal skeletal accumulation of bisphosphonate is possible [14].

Men with osteoporosis: Alendronate and zoledronic acid are FDA-approved for men with osteoporosis. Holiday protocols in men follow the same framework as postmenopausal women because the pharmacokinetics do not differ by sex. Testosterone deficiency should be corrected before or concurrent with bisphosphonate initiation, as hypogonadism independently drives bone loss.

Atypical femoral fracture survivors: Any patient who has sustained an AFF should stop bisphosphonate therapy immediately and not restart the same drug class. Teriparatide 20 mcg daily subcutaneously for 24 months is the preferred next-line agent in this setting, as it actively stimulates osteoblast-mediated cortical repair [15].

Communicating the Holiday to Patients

Patient understanding of the holiday concept determines adherence. Several patients interpret "stop the medication" as meaning that treatment has worked completely and no further monitoring is needed. A clear verbal and written explanation should cover three points: first, the pause is planned and time-limited, not permanent discontinuation; second, calcium, vitamin D, and lifestyle measures continue without any pause; and third, a DXA scan is scheduled before the holiday ends, not just at the start.

A 2021 survey published in Osteoporosis International found that 43% of patients who stopped bisphosphonates had done so without physician guidance, and among those, follow-up DXA adherence was below 20% [16]. Structured holiday counseling at the time of the stop decision, with a calendar reminder system for the end-of-holiday DXA, improved return-to-monitoring rates by approximately 30% in the same analysis.

Practical Prescribing Checklist Before Starting a Holiday

Before finalizing a holiday plan, the prescribing clinician should confirm each of the following:

• Baseline DXA completed within the prior 12 months with T-score documented at total hip, femoral neck, and lumbar spine
• FRAX score recalculated using current BMD values
• Bone turnover markers (CTX or NTX) measured fasting, to serve as a reference for mid-holiday comparison
• Vitamin D level checked; deficiency corrected before the holiday begins
• Lateral spine imaging reviewed for prevalent vertebral fractures not captured by DXA alone
• Medication reconciliation: proton pump inhibitors, loop diuretics, aromatase inhibitors, and glucocorticoids all independently affect bone loss rate and may raise the required monitoring frequency
• Patient counseled verbally and in writing; next DXA date entered in the chart as a hard order, not a recommendation

In patients with a femoral neck T-score below -2.0 but above -2.5, the ASBMR recommends considering continued therapy with IV zoledronic acid every 18 to 24 months rather than a full holiday, effectively halving the annual dose burden while maintaining measurable fracture protection [1].