NUR 602 Module 6 Case Analysis Example

Two Drugs Pulling Against Each Other: A Case Analysis of Donepezil, Oxybutynin and Urgency in an 81-Year-Old Woman

[Student Name]

Southern New Hampshire University

NUR 602: Advanced Pharmacology Across the Life Span

Module Six Case Analysis

[Instructor Name]

[Date]

The organization, setting and figures below are a composite written as a model document. No real employer, client, colleague or patient is described.

Two Drugs Pulling Against Each Other: A Case Analysis of Donepezil, Oxybutynin and Urgency in an 81-Year-Old Woman

Older adults are the group most likely to experience a prescribing cascade, in which the side effect of one medicine is read as a fresh illness and answered with a second medicine. When the two drugs act on the same receptor in opposite directions, the cascade can cancel the benefit of the first drug and add harm from the second. This case analysis examines an 81-year-old woman on donepezil and oxybutynin. It argues that her urgency is most likely a cholinergic effect of donepezil, that oxybutynin is working against her memory treatment and that behavioral therapy with a non-anticholinergic drug if needed is the safer path.

Case Summary

Evelyn is 81; she lives on her own, and her son stops by each afternoon. Eight months ago she was diagnosed with mild cognitive impairment likely due to Alzheimer disease, with a Montreal Cognitive Assessment score of 24. Donepezil 5 mg nightly was started three months ago. About six weeks later she developed urinary urgency with leaking two or three times a day, and she began limiting fluids. At an urgent care visit a month ago, a urinalysis was negative and she was prescribed oxybutynin immediate release 5 mg twice daily. Her son reports that she now seems more forgetful, has a dry mouth and that her bowels now move only about twice a week. Her repeat assessment score today is 21. Her other medicines are lisinopril 10 mg and a daily calcium and vitamin D tablet. Her blood pressure is 132/78, and her kidney function is modestly reduced, with an eGFR of 58. A bladder scan after voiding shows 40 mL.

Identifying the Cascade

The timeline points to donepezil. Cholinesterase inhibitors raise acetylcholine at muscarinic receptors throughout the body, including the detrusor muscle, and new or worse urinary incontinence is a recognized effect. In a population cohort of older adults with dementia, those dispensed a cholinesterase inhibitor were more likely to be prescribed an anticholinergic drug afterward than those who were not, with an adjusted hazard ratio of 1.55, which the authors described as a prescribing cascade (Gill et al., 2005). Evelyn's urgency began within weeks of starting donepezil, and her urinalysis and bladder scan found no other cause. Other explanations deserve a brief check before the cascade is accepted. She takes no diuretic, her fasting glucose last month was 94 mg/dL, she has no new neurological signs and the low residual volume argues against retention with overflow. Her fluid restriction may even have concentrated her urine and made urgency worse. None of these alternatives fits the timing as well as the drug does.

Oxybutynin then blocks the same muscarinic receptors that donepezil is trying to stimulate. Immediate-release oxybutynin crosses the blood-brain barrier readily, and her dry mouth and constipation show that it is having systemic effects. The fall in her cognitive score is not proof of drug harm, but the timing is consistent with it. Oxybutynin is listed in the 2023 Beers Criteria as a strongly anticholinergic drug to avoid in older adults, particularly with cognitive impairment (American Geriatrics Society Beers Criteria Update Expert Panel, 2023).

The Longer-Term Concern

Beyond short-term confusion, cumulative anticholinergic exposure has been linked to dementia. In a prospective cohort of 3,434 adults aged 65 and older, the highest level of cumulative strong anticholinergic use over ten years was associated with a hazard ratio of 1.54 for dementia compared with no use, with a dose-response pattern; bladder antimuscarinics were among the most commonly used classes (Gray et al., 2015). The study is observational and cannot prove causation, but for a woman already being treated for cognitive decline, it is a strong reason not to add years of anticholinergic exposure.

Options for Her Bladder

Behavioral therapy is the first-line treatment for overactive bladder, according to the AUA and SUFU guideline, and it may be combined with drugs from the start (Cameron et al., 2024). Its effect is not small. In a randomized trial of older women with urge incontinence, behavioral treatment reduced incontinence episodes by a mean of 80.7%, compared with 68.5% for oxybutynin and 39.4% for placebo, and patients were more satisfied with it (Burgio et al., 1998). For Evelyn, timed voiding every two to three hours, urge suppression and steady fluid intake spread through the day are practical, and her son can help set reminders.

If drug therapy is still needed, a beta-3 agonist avoids muscarinic blockade altogether. In a 12-week trial in community-dwelling adults aged 65 and older, mirabegron reduced incontinence episodes and urinary frequency more than placebo and was well tolerated (Wagg et al., 2020). Mirabegron can raise blood pressure slightly and inhibits the enzyme CYP2D6, so it needs a pressure check and a review of interacting drugs. Vibegron 75 mg daily has no known effect on CYP2D6 and no dose adjustment for her kidney function, which makes it a simpler choice if her insurance covers it.

Plan

Stop oxybutynin now; the immediate-release form does not require a taper. Continue donepezil, because it is her only treatment for cognitive decline, but discuss with her and her son whether its benefit is worth the bladder effect if urgency persists. Begin timed voiding and bladder training with written instructions and a three-day bladder diary. Treat constipation with fluids, fiber and polyethylene glycol, because a full rectum worsens urgency. If leaking still limits her life after four weeks, start vibegron 75 mg daily. Review in two weeks by phone and in eight weeks in person, repeating the cognitive assessment and the bladder diary so that change in both can be measured.

Conclusion

Evelyn's second prescription answered a side effect of her first and then worked against it. Recognizing the cascade, removing the anticholinergic, relying on behavioral therapy and choosing a beta-3 agonist if a drug is needed protects both her bladder and her memory. The larger lesson for primary care is to ask whether any new symptom in an older adult began after a recent drug change, and to ask it before writing the next prescription rather than after.

References

American Geriatrics Society Beers Criteria Update Expert Panel. (2023). American Geriatrics Society 2023 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. Journal of the American Geriatrics Society, 71(7), 2052-2081. https://doi.org/10.1111/jgs.18372

Burgio, K. L., Locher, J. L., Goode, P. S., Hardin, J. M., McDowell, B. J., Dombrowski, M., & Candib, D. (1998). Behavioral vs drug treatment for urge urinary incontinence in older women: A randomized controlled trial. JAMA, 280(23), 1995-2000. https://doi.org/10.1001/jama.280.23.1995

Cameron, A. P., Chung, D. E., Dielubanza, E. J., Enemchukwu, E., Ginsberg, D. A., Helfand, B. T., Linder, B. J., Reynolds, W. S., Rovner, E. S., Souter, L., Suskind, A. M., Takacs, E., Welk, B., & Smith, A. L. (2024). The AUA/SUFU guideline on the diagnosis and treatment of idiopathic overactive bladder. Journal of Urology, 212(1), 11-20. https://doi.org/10.1097/JU.0000000000003985

Gill, S. S., Mamdani, M., Naglie, G., Streiner, D. L., Bronskill, S. E., Kopp, A., Shulman, K. I., Lee, P. E., & Rochon, P. A. (2005). A prescribing cascade involving cholinesterase inhibitors and anticholinergic drugs. Archives of Internal Medicine, 165(7), 808-813. https://doi.org/10.1001/archinte.165.7.808

Gray, S. L., Anderson, M. L., Dublin, S., Hanlon, J. T., Hubbard, R., Walker, R., Yu, O., Crane, P. K., & Larson, E. B. (2015). Cumulative use of strong anticholinergics and incident dementia: A prospective cohort study. JAMA Internal Medicine, 175(3), 401-407. https://doi.org/10.1001/jamainternmed.2014.7663

Wagg, A., Staskin, D., Engel, E., Herschorn, S., Kristy, R. M., & Schermer, C. R. (2020). Efficacy, safety, and tolerability of mirabegron in patients aged 65 yr or older with overactive bladder wet: A phase IV, double-blind, randomised, placebo-controlled study (PILLAR). European Urology, 77(2), 211-220. https://doi.org/10.1016/j.eururo.2019.10.002