What is the best course of action for an elderly patient on Eliquis (apixaban) and Fosamax (alendronate) with a normal vitamin B12 level?

Vitamin B12 Level of 195 pg/mL in Elderly Patient on Eliquis and Fosamax

This B12 level of 195 pg/mL is borderline-low and warrants treatment, particularly given the patient's elderly status and medication regimen that may affect B12 absorption.

Assessment of Current B12 Status

Your patient's B12 level of 195 pg/mL falls in the indeterminate range (180-350 pg/mL), where functional deficiency may exist despite not being overtly low 1. Elderly patients are at particularly high risk, with metabolic B12 deficiency present in 18.1% of patients over 80 years, and up to 50% of individuals with "normal" serum B12 may have functional deficiency when measured by methylmalonic acid (MMA) 2, 3.

Key Medication Considerations

• Fosamax (alendronate) and other bisphosphonates can contribute to gastrointestinal issues that may impair B12 absorption, though this is not a direct mechanism 1
• Proton pump inhibitors or H2 blockers (if the patient is taking these alongside Fosamax) impair B12 absorption when used >12 months 4
• Elderly patients have a 20% prevalence of atrophic gastritis causing food-bound B12 malabsorption 5, 6

Recommended Diagnostic Approach

Measure methylmalonic acid (MMA) to confirm functional B12 deficiency, as this is the most sensitive marker and will detect the additional 5-10% of patients with true deficiency despite borderline serum levels 1, 2.

• MMA >271 nmol/L confirms functional B12 deficiency with 98.4% sensitivity 1, 2
• Alternatively, measure homocysteine (target <10 μmol/L), though this is less specific than MMA 1, 2
• Check complete blood count for macrocytosis or megaloblastic anemia, though these may be absent in one-third of cases 2, 7

Clinical Symptom Assessment

Evaluate specifically for 2, 4:

• Neurological symptoms: paresthesias, numbness, gait disturbances, cognitive difficulties, memory problems
• Hematologic findings: fatigue, weakness, glossitis
• Visual problems: blurred vision or optic nerve dysfunction

Treatment Recommendations

If MMA is Elevated (>271 nmol/L) or Patient is Symptomatic

Initiate oral vitamin B12 supplementation at 1000-2000 mcg daily, which is as effective as intramuscular administration for most patients, including those with malabsorption 2, 4, 6.

• For patients with neurological symptoms: Consider intramuscular hydroxocobalamin 1000 mcg on alternate days until symptoms improve, then transition to maintenance 1, 8, 7
• For asymptomatic patients with confirmed deficiency: Oral B12 1000-2000 mcg daily for 3 months, then reassess 5, 4

Maintenance Therapy

After initial treatment 1, 8:

• Oral maintenance: 250-500 mcg daily for dietary insufficiency
• For malabsorption: Continue 1000 mcg daily orally OR hydroxocobalamin 1000 mcg IM every 2-3 months
• Given the patient's age and potential atrophic gastritis, lifelong supplementation will likely be required 5, 6

Special Considerations for Anticoagulation

Eliquis (apixaban) does not contraindicate intramuscular B12 injections if needed, but requires precautions 9:

• Use smaller gauge needles (25-27G) for IM injection 1
• Apply prolonged pressure (5-10 minutes) at injection site 1
• Monitor injection sites for hematoma formation 1
• Oral high-dose B12 is preferred in anticoagulated patients to avoid injection-related bleeding risk 4, 6

Monitoring Schedule

• Recheck B12 and MMA at 3 months after initiating supplementation 1, 8
• Recheck again at 6 and 12 months in the first year 1
• Transition to annual monitoring once levels stabilize 1, 8
• Monitor complete blood count to assess resolution of any hematologic abnormalities 1

Critical Pitfalls to Avoid

• Never administer folic acid before ensuring adequate B12 treatment, as folic acid can mask B12 deficiency anemia while allowing irreversible neurological damage to progress 1, 8, 3
• Do not rely solely on serum B12 to rule out deficiency in elderly patients, as metabolic deficiency is common despite "normal" levels 2, 3
• Do not discontinue supplementation even if levels normalize, as elderly patients with malabsorption require lifelong therapy 1, 5
• Metformin use >4 months warrants B12 monitoring - verify if patient is diabetic and on metformin, as this is a common cause of deficiency 10, 4