Understanding and preventing drug interactions in elderly patients

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Abstract

The elderly consume a disproportionate amount of prescription and nonprescription medications. Alterations in physiology, polypharmacy, multiple prescribers, and other factors place the elderly population at risk of developing clinically significant drug–drug interactions. The incidence of potential drug–drug interactions increases with increased drug use and are responsible for numerous emergency room and physician visits. Drug interactions have been shown to cause a decline in functional abilities in older people. Drugs can interact to alter the absorption, distribution, metabolism, or excretion of a drug or interact in a synergistic or antagonist fashion altering their pharmacodynamics. Drug interactions are often clinically unrecognized and responsible for increased morbidity in elderly patients. Prudent use of medications and vigilant drug monitoring are essential to avoid drug–drug interactions.

Introduction

Drugs, foods, and nutritional supplements can alter the pharmacological actions of a medication. These alterations may cause a drug’s action to be diminished or enhanced. Drug interactions that decrease the effectiveness of a drug are often overlooked and explained as worsening disease or poor medication adherence [1]. In a nursing home setting, 70% of the potential drug interactions involved some loss of action of one or more drugs [2]. Drugs may also interact with diseases, potentially worsening disease symptoms. This review focuses on drug–drug interactions, where one drug has the potential to interfere with the pharmacological actions of another drug. Common mechanisms of drug–drug interactions are discussed and strategies for prevention are listed. In particular, the focus is on the aging population, as they use a disproportionate amount of medications and have the highest risks for severe adverse outcomes from their drug therapy [3], [4], [5]. Chronic disease, physiologic changes associated with aging, and altered pharmacokinetic and pharmacodynamic consequences of aging place elderly patients at high risk for adverse events from drug–drug interactions. Examples of common drug interactions in elderly patients that have potential clinical significance are discussed.

Section snippets

Aging physiology

Due to disease and aging physiology, renal elimination and liver metabolism of drugs may be impaired in many elderly patients. These alterations in pharmacokinetics in the elderly may contribute to an exaggeration in the consequences from drug–drug interactions. For example, in a middle-aged individual, a small inhibition in drug metabolism caused by a drug interaction might have no clinical consequence. However, in a very elderly person who may have reduced drug metabolism from a normal aging

Emergency department visits

Recent data on the incidence of potential drug–drug interactions in community-dwelling elderly is difficult to find. Data are available from several studies conducted in emergency departments. Goldberg et al. [16] retrospectively reviewed medical records of patients seen in two emergency departments. During the data collection period, all patients using three or more medications and all patients over 50 years using at least two medications were included in the study. Drug regimens were reviewed

Altered absorption

Drug interactions can occur where one drug changes the absorption characteristics of another drug. The binding of one drug to another, changes in gastric pH, and changes in gastrointestinal motility can cause these drug interactions. The classic example of a drug binding another drug is that of tetracycline and calcium and magnesium containing antacids. The cations of the antacid bind the antibiotic molecule to prevent its absorption potentially causing a treatment failure. Absorption of many

Most frequently prescribed drugs in the elderly and their interactions

Table 2 lists the 10 most frequently prescribed drugs to elderly patients in the US and selected drug interactions that can occur with these drugs. This is a partial list of drug interactions that can occur with other commonly prescribed drugs. All of these interactions have the potential to be clinically significant and cause untoward events, particularly when their occurrence is not monitored.

Top 10 drug interactions in long-term care facilities

The American Society of Consultant Pharmacists and the American Medical Directors Association conducted a survey among their members to identify the top 10 most dangerous drug interactions they see in their long-term care facility practices. The list shown in Table 3 was finalized based on the frequency of drug use in the long-term care setting, and on the potential for adverse consequences of the drug interaction [64].

Selected drug interactions involving chemotherapeutic agents

Table 4 lists drug–drug interactions involving chemotherapeutic drugs. This partial list of interactions contains only those interactions that may potentially harm patients and where some data exist describing the possible negative clinical consequences.

Preventing drug–drug interactions

The number of drugs used to treat elderly patients must be minimized to reduce the incidence of adverse reactions, potential drug–drug interactions, and adherence difficulties while at the same time minimizing costs associated to with pharmacotherapy. Use of hand-held personal digital assistants (PDAs) and other computer applications can be helpful to screen for potential drug–drug interactions. It is easy to overlook a potential drug interaction, particularly those that negate a therapeutic

Jeffrey C. Delafuente graduated from the University of Florida College of Pharmacy with a B.S. in pharmacy in 1973 and a M.S. in clinical pharmacy in 1976. After completing a 2-year fellowship in clinical immunology at the University of Florida College of Medicine, he joined the faculties at St. Louis University School of Medicine and the St. Louis College of Pharmacy. In 1984, he joined the faculties of the University of Florida Colleges of Pharmacy and Medicine where he was professor and

References (68)

  • W.A Armstrong et al.

    Analysis of drug–drug interactions in a geriatric population

    Am. J. Hosp. Pharm.

    (1980)
  • J.T Hanlon et al.

    Adverse drug events in high risk older outpatients

    J. Am. Geriatr. Soc.

    (1997)
  • L.A Bero et al.

    Characterization of geriatric drug-related hospital readmissions

    Med. Care

    (1991)
  • R.B Stewart et al.

    Polypharmacy in the aged. Practical solutions

    Drugs Aging

    (1994)
  • M.E Corcoran

    Polypharmacy in the older patient with cancer

    Cancer Control

    (1997)
  • C.W Burt

    National trends in use of medications in office-based practice

    Health Affairs

    (1985–1999)
  • R.A Bell et al.

    Direct-to-consumer prescription drug advertising and the public

    J. Gen. Intern. Med.

    (1999)
  • Bedell SE, Jaabbour S, Goldberg R, et al. Discrepancies in the use of medications. Their extent and predictors in an...
  • J Feely et al.

    Altered pharmacodynamics in the elderly

    Clin. Pharmacol.

    (1990)
  • F Pucino et al.

    Pharmacogeriatrics

    Pharmacotherapy

    (1985)
  • Hanlon JT, Gray SL, Schmader KE. Adverse drug reactions. In: Delafuente JC, Stewart RB, editors. Therapeutics in the...
  • J Doucet et al.

    Drug–drug interactions related to hospital admissions in older adults: a prospective study of 1000 patients

    J. Am. Geriatr. Soc.

    (1996)
  • J.T Hanlon et al.

    Impact of inappropriate drug use on mortality and functional status in representative community dwelling elders

    Med. Care

    (2002)
  • Hansten PD. Appendix II: important drug interactions. In: Katzung BG, editor. Basic and clinical pharmacology. 6th ed....
  • Benet LZ, Mitchell JR, Sheiner LB. Pharmacokinetics: the dynamics of drug absorption, distribution, and elimination....
  • N.K Wadhwa et al.

    The effect of oral metoclopramide on the absorption of cyclosporine

    Transplant Proc.

    (1987)
  • B.F Johnson et al.

    Effect of metoclopramide on digoxin absorption from tablets and capsules

    Clin. Pharmacol. Ther.

    (1984)
  • R.L O’Connor-Semmes et al.

    Effect of ranitidine on the pharmacokinetics of triazolam and a-hydroxytriazolam in both young (19–60 years) and older (61–78 years) people

    Clin. Pharmacol. Ther.

    (2001)
  • A.R Moore et al.

    Drug-induced cognitive impairment in the elderly

    Drugs Aging

    (1999)
  • W.A Ray et al.

    Psychotropic drug use and the risk of hip fracture

    N. Engl. J. Med.

    (1987)
  • M.E Tinetti et al.

    Risk factors for falls among elderly persons living in the community

    N. Engl. J. Med.

    (1988)
  • D.A Flockhart et al.

    Implications of cytochrome P450 interactions when prescribing medication for hypertension

    Arch. Intern. Med.

    (2002)
  • E.L Michalets

    Update: clinically significant cytochrome P-450 drug interactions

    Pharmacotherapy

    (1998)
  • Chapron DJ. Drug disposition and response. In: Delafuente JC, Stewart RB, editors. Therapeutics in the elderly. 3rd ed....

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    Jeffrey C. Delafuente graduated from the University of Florida College of Pharmacy with a B.S. in pharmacy in 1973 and a M.S. in clinical pharmacy in 1976. After completing a 2-year fellowship in clinical immunology at the University of Florida College of Medicine, he joined the faculties at St. Louis University School of Medicine and the St. Louis College of Pharmacy. In 1984, he joined the faculties of the University of Florida Colleges of Pharmacy and Medicine where he was professor and associate chairman of pharmacy practice, and in 1998 he became professor and director of geriatric programs at the Virginia Commonwealth University School of Pharmacy in Richmond Virginia.

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