IHP 310 Module 2 Cardiovascular and Hematopoietic Case Study example

Two Problems, Two Prescriptions: A Case Study of Amlodipine Edema and Metformin-Associated Vitamin B12 Deficiency in a 67-Year-Old Man

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Southern New Hampshire University

IHP 310: Pathophysiology and Pharmacology Concepts

Module Two Case Study

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[Date]

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Two Problems, Two Prescriptions: A Case Study of Amlodipine Edema and Metformin-Associated Vitamin B12 Deficiency in a 67-Year-Old Man

The Patient Record

Mr. Kowalski is a composite 67-year-old retired bus mechanic with type 2 diabetes diagnosed nine years ago and hypertension diagnosed six years ago. He has taken metformin, 1,000 mg in the morning and evening, for eight years, and his amlodipine dose was doubled to 10 mg a year ago because his pressure stayed above goal. At a routine visit he reports that his ankles swell by evening, that he is tired climbing stairs and that his feet have felt numb and tingly for several months. His blood pressure is 132/78 mmHg, his hemoglobin A1c is 7.1 percent, and his hemoglobin is 11.2 g/dL and his red cells are enlarged, with an MCV of 106 fL, a picture of macrocytic anemia. His vitamin B12 level is low at 168 pg/mL. His kidney function is normal.

The Cardiovascular Problem: Hypertension and Ankle Edema

Hypertension reflects increased resistance in the small arteries, often with stiffening of larger arteries over time. Sustained high pressure damages blood vessels and increases the risk of stroke, heart attack, heart failure and kidney disease. Guidelines recommend treating adults with diabetes and hypertension to a target below 130/80 mmHg, using first-line classes that include calcium channel blockers, thiazide diuretics, and angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (Whelton et al., 2018).

Amlodipine is a dihydropyridine calcium channel blocker. It blocks calcium entry into vascular smooth muscle, relaxing the arteries and lowering resistance. It dilates the arterioles that feed capillaries more than the veins that drain them, so pressure within leg capillaries rises and fluid moves into the tissues. The ankle swelling began after his dose was doubled, a timing that points to the drug rather than to heart or kidney failure, especially with normal kidney function. Because the edema is caused by capillary pressure rather than fluid overload, diuretics work poorly for it.

The Hematopoietic Problem: Vitamin B12 Deficiency

Vitamin B12 is needed for DNA synthesis in rapidly dividing cells, including red blood cell precursors in the bone marrow, and for maintaining the myelin that insulates nerves. When B12 is lacking, precursors cannot divide normally and grow into large, fragile red cells, producing macrocytic anemia, which explains his fatigue and MCV of 106. The same deficiency can damage peripheral nerves, causing numbness and tingling in the feet.

Years of metformin therapy tend to lower B12 levels, most likely because the drug reduces absorption of the vitamin in the terminal ileum. In a large secondary analysis of a diabetes prevention trial, each year of metformin use was associated with a 13 percent increase in the odds of B12 deficiency (Aroda et al., 2016). Diabetes guidelines therefore recommend periodic measurement of B12 in people taking metformin, particularly those with anemia or neuropathy (American Diabetes Association [ADA], 2024). Mr. Kowalski's numb feet could easily have been attributed to diabetic neuropathy, but his A1c is near target and the anemia with large cells points to B12 deficiency as at least a contributing cause.

Medication Review

The table below reviews each medication.

Table 1

Medication Review for Mr. Kowalski

Recommendations

Three changes follow from the analysis. First, reduce amlodipine to 5 mg and add an angiotensin receptor blocker or ACE inhibitor. This combination targets two mechanisms of blood pressure, and blocking angiotensin dilates veins as well as arteries, which reduces the capillary pressure that causes calcium channel blocker edema. Kidney function and potassium should be checked after starting. Second, continue metformin, which is controlling his diabetes, and start vitamin B12 replacement, with a repeat B12 level and blood count in about three months to confirm the anemia is improving. Third, examine his feet and reassess the numbness after B12 is replaced; if symptoms persist, diabetic neuropathy is also likely and needs its own plan.

Choosing the B12 Replacement

Vitamin B12 can be replaced by injection or by mouth. Injections bypass the gut and were long the standard, particularly for pernicious anemia, in which the stomach no longer produces the intrinsic factor needed for normal absorption. In deficiency linked to metformin, absorption is reduced rather than absent, and high oral doses can be absorbed by passive diffusion, so daily oral tablets are a reasonable, inexpensive option that avoids clinic visits. The choice should consider how severe the deficiency is, whether nerve symptoms are present, and how reliably the patient takes daily medicines. Because Mr. Kowalski has both anemia and nerve symptoms, a clinician might begin with injections to restore stores quickly and then switch to oral maintenance. Either way, the chart should record the plan to recheck blood counts and B12, since response confirms the diagnosis.

What the Chart Teaches a Health System

Both problems in this chart were predictable effects of long-term medications, and both were found at a routine visit rather than by a monitoring system. A practice can prevent similar cases by adding an electronic health record reminder for B12 testing in patients on metformin for several years and by flagging patients on high-dose amlodipine for review at each visit. These are low-cost changes that turn a clinician's memory into a reliable process, which is the kind of improvement a health care manager can lead.

Conclusion

Mr. Kowalski's swollen ankles and anemia both trace to drugs he needs. Amlodipine lowers his blood pressure by relaxing arteries but, at a higher dose, raises capillary pressure and causes edema. Metformin controls his glucose but, over eight years, has likely depleted his vitamin B12, producing macrocytic anemia and possibly nerve symptoms. Adjusting the antihypertensive regimen and replacing B12, while keeping metformin, addresses both problems.

References

American Diabetes Association. (2024). 9. Pharmacologic approaches to glycemic treatment: Standards of care in diabetes-2024. Diabetes Care, 47(Suppl. 1), S158-S178. https://doi.org/10.2337/dc24-S009

Aroda, V. R., Edelstein, S. L., Goldberg, R. B., Knowler, W. C., Marcovina, S. M., Orchard, T. J., Bray, G. A., Schade, D. S., Temprosa, M. G., White, N. H., Crandall, J. P., & Diabetes Prevention Program Research Group. (2016). Long-term metformin use and vitamin B12 deficiency in the Diabetes Prevention Program Outcomes Study. Journal of Clinical Endocrinology & Metabolism, 101(4), 1754-1761. https://doi.org/10.1210/jc.2015-3754

Whelton, P. K., Carey, R. M., Aronow, W. S., Casey, D. E., Jr., Collins, K. J., Dennison Himmelfarb, C., DePalma, S. M., Gidding, S., Jamerson, K. A., Jones, D. W., MacLaughlin, E. J., Muntner, P., Ovbiagele, B., Smith, S. C., Jr., Spencer, C. C., Stafford, R. S., Taler, S. J., Thomas, R. J., Williams, K. A., Sr., . . . Wright, J. T., Jr. (2018). 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA guideline for the prevention, detection, evaluation, and management of high blood pressure in adults. Hypertension, 71(6), e13-e115. https://doi.org/10.1161/HYP.0000000000000065