Complications of Adverse Drug Reactions may include hospitalization, increased hospital stays and health care expenditures, morbidity, and death. The incidence of Adverse Drug Reactions varies by type of health care setting (e.g., ambulatory clinic, hospital, nursing home). In a cohort of older Medicare enrollees, the rate of Adverse Drug Reactions was 50.1 per 1,000 person years. In long-term care facilities, the rates of Adverse Drug Reactions were reported as 1.9 to 9.8 per 100 resident-months. Adverse Drug Reactions are a common cause of hospital admission of older adults and were responsible for 6% to 24% of all hospital admissions. Of all Adverse Drug Reactions, 23% to 28% were categorized as serious.
Approximately one quarter to one half of Adverse Drug Reactions are considered to be preventable. Errors are most likely to occur at the time of prescribing a medication or during monitoring of therapy. Prescribing errors include choosing an inappropriate medication, prescribing a medication that interacts with another medication in the individual’s regimen, and prescribing a drug in the face of an established drug allergy. Errors in monitoring of therapy may include failing to obtain necessary laboratory values to monitor drug therapy and not responding promptly to signs, symptoms, or laboratory evidence of drug toxicity.
Many researchers have attempted to identify risk factors for Adverse Drug Reactions, an endeavor that has been disappointing. The most persistent risk factor for Adverse Drug Reactions is use of multiple medications; thus, it is important that patients be maintained on the fewest number of medications needed to manage their health conditions. Researchers have not found Adverse Drug Reactions to vary substantially according to age or sex. Several factors are important to keep in consideration to minimize Adverse Drug Reactions, even though they have not been identified as independent risk factors. Prescribers should keep in mind the age related changes in kidney and liver function that may cause the body to be less efficient in eliminating medications and should adjust medication doses appropriately in older adults. Although specific medication types have not consistently been identified as independent risk factors for Adverse Drug Reactions, certain medications may be more likely to cause Adverse Drug Reactions if they have a narrow therapeutic window; for example, a blood level that causes the desired pharmacological effect may be similar to the blood level that causes Adverse Drug Reactions.
Identifying Adverse Drug Reactions in older adults may be challenging, especially in frail older adults. In some cases, Averse Drug Reaction symptoms may present nonspecifically or be attributed to other causes. For example, a drug may be overlooked as the cause of cognitive impairment or of an increase in falls. Older individuals often have multiple chronic health conditions and take several medications, making it difficult to determine whether a new symptom is related to a new health condition, is related to an existing health condition, or is an Averse Drug Reaction. Thus, medication use should be routinely considered as a possible explanation for any new symptom that occurs in older adults.
