Medication Issues

The value of the equation is usually reduced to 85% in women. While many electronic medical record systems report Cr Cl via the Cockcroft–Gault equation, the clinician must remember that the equation become less reliable in situations of low flow and low muscle mass which are commonly seen in older frail patients. Whenever possible, measurement of blood levels of drugs (aminoglycosides, anticonvulsants) in older patients is the best guide to dosing levels.

Pharmacodynamics, the time course and intensity of effect can vary widely and unpredictably in older patients. Morphine can produce slightly longer pain relief in some older patients, for example. Adjustments in initial dose and dosing intervals may be required for many medications.

When initiating a new medication in an older patient, the adage “start low, go slow” remains useful: start with small initial doses, with longer dose intervals; increase dose or alter intervals as symptoms require. Table 4.1 summaries these principles.

Table 4.1

Summary of pharmacokinetic changes with aging

	Age-associated change	Medication examples
Absorption	Increased possibility of drug–drug interactions in GI tract (polypharmacy)	Proton pump inhibitors and antibiotics, calcium salts and synthroid
Distribution	Increased body fat stores	Anesthetic agents-warfarin, phenytoin
Distribution	Decreased albumin concentration and drug binding	Anesthetic agents-warfarin, phenytoin
Metabolism	Decreased liver metabolism	Benzodiazepines
Elimination	Decreased renal clearance	Aminoglycosides, anticonvulsants

The “Correct” Patient

Choosing the best medication at the right dose and dosing interval for your individual patient is the foundation of prescribing for patients of any age. In selecting a medication for an older patient, certain factors may influence the choice of an initial medication:

Effectiveness—New drugs are rarely tested in older patients due to age-based elimination from initial drug study panels. While the FDA is encouraging more inclusive criteria in patient selection for initial testing, issues of coexisting disease will likely continue to limit the inclusion of representative older patients in studies. Prescribing a newly licensed drug to older patients requires the ability of the patient and physician to identify and monitor both effectiveness and side effects in this population. Often, the choice of an established medication is safer for an older patient.

Harms:

Adverse effects of newly licensed medications are unpredictable in older patients
Certain classes of medications are more likely to cause an adverse effect in an older patient
- Anticholinergic drugs may precipitate acute glaucoma, bladder outlet obstruction, bradycardias, and syncope. Donepezil prescribed for memory loss is increasingly reported as linked to bradyarrhythmias and syncope
- Opiods will increase constipation, and may cause confusion
- Antibiotic use may result in bacterial overgrowth colitis

A commonly used source of medications to be potentially avoided in older adults is the “Beers list” [3, 4]. A sample of drugs appearing on the list with rationale appears in Table 4.2. If an individual patient has a strong preference for a medication on the Beer’s list, chart documentation of the rational should be provided.

Table 4.2

A sample of potentially inappropriate drugs for the elderly from the Beer’s list

Medication class	Example	Rationale
Nonsteroidal anti-inflammatory agents	Naproxen	Renal failure, GI bleeding
Barbiturates	Phenobarbital	Confusion
Benzodiazepines	Chlordiazepoxide, diazepam	Prolonged sedation
Hypnotics	Diphenhydramine, flurazepam	Confusion, prolonged sedation
Muscle relaxants	Cyclobenzaprine, methocarbamol	Anticholinergic effects
Pain relievers	Meperidine, propoxyphene	Confusion, minimal benefit
Antihypertensives	Clonidine	Bradycardia, orthostatic hypotension

Drug–drug interactions are more likely due to the increased average number of medications taken by older patients.

Cost—Many older patients are on limited income, and take multiple medications. Most seniors are now using insurance plans with established formularies to help pay for medications; either Medicare “Part D” plans or state Medicaid formularies. Established medications are more likely to be included in these formularies and require less staff time with preauthorization for use.

Adherence: “Affordable Cost” and Other Factors

Older patients may experience special barriers to filling prescriptions and continuing medications as prescribed. Studies have shown that approximately 50% of older patients have adherence issues with at least one medication. Complicating things further, patients may be non-adherent with one medication and adherent with others [5]!

Cost—Pharmacy data suggests that as many as 40% of prescriptions are never “picked-up” by patients. Cost is a major factor in this initial loss of adherence, as well as with ongoing care. As mentioned above, older patients are on a fixed income, and use insurance-based formularies for medications payment. Many of these insurance plans require co-payments for medications. With increasing numbers of prescribed medications, the co-payment amounts may become limiting. Prescribing generic forms of medications whenever possible will aid in this aspect of care.

Literacy—Standard prescription labels are too small for many older patients to read, and use medical words which are poorly understood. Some of the larger chain store pharmacies have instituted larger print, more legible labeling practices. Physician offices can assist by providing large print medication lists with instructions for patients at the time of visits.

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