Drug Interactions in Older Adults: Mechanisms and Risk Factors for Consultant Pharmacists

At the conclusion of this course, participants will be able to:

1. Identify the relationship between medication count and drug interaction risk in older adults.

2. Differentiate the cytochrome P450 enzymes and drug transporters that most commonly mediate pharmacokinetic drug interactions.

3. Describe the pharmacodynamic mechanisms that produce additive drug interaction toxicity.

4. Evaluate how patient-specific modifiers alter an individual patient's drug interaction risk.

5. Select the most appropriate recommendation in response to a clinically significant drug interaction alert.

Drug interactions in older adults arise through identifiable mechanisms, including inhibition or induction of cytochrome P450 enzymes, interference with drug transporters, and additive pharmacodynamic effects on cardiac conduction, serotonergic tone, and central nervous system depression. Patient-specific factors, including pharmacogenomic phenotype, sex, age-related physiologic change, and organ function, determine how much of that theoretical risk reaches an individual patient. This course examines those mechanisms and modifiers, and the process of converting an automated interaction alert into an individualized, documented recommendation in consultant pharmacist practice. Instruction is anchored in the therapeutic classes in which these interactions carry the greatest consequence for older adults, including HMG-CoA reductase inhibitors (statins), opioid analgesics, benzodiazepines and other sedative-hypnotics, serotonergic antidepressants, QTc-prolonging agents, and prodrugs such as codeine that depend on CYP2D6 for activation.

After completing the activity, consultant pharmacists should be better prepared to distinguish interaction mechanisms, assess how patient characteristics change risk, evaluate clinically significant alerts, and document recommendations that support safer medication use. The course addresses the gap between receiving an automated interaction alert and making an individualized, evidence-supported recommendation.

Instruction is delivered as written lessons with embedded video segments drawn from a recorded AchieveCE webinar and six short supplemental segments Dr. Garofoli recorded for this course. Each written lesson stands alone. The video segments illustrate and extend the written instruction rather than replacing it. Where the recording predates current guidance, a labeled Notes section identifies the corrected statement, and the corrected statement is the basis for assessment.

This activity addresses Fla. Admin. Code R. 64B16-26.302(1)(a), Drug, Disease State Information, with emphasis on drug interaction pharmacology. Content is drawn from national guidance and applies to consultant pharmacists practicing in any U.S. state.