2 Adverse Drug Reactions and Drug–Drug Interactions
Associated with Antimicrobial Agents
2.1 Adverse Drug Reactions
ADRs are defined as injuries occurring as a result of
medication use [24]. Aging is associated with an increased
frequency of chronic disease and declining functional status.
Additionally, the occurrence of multiple chronic conditions
in older patients leads to polypharmacy [25–28].
ADRs are very common in elderly persons, and polypharmacy
increases the risk of ADRs [29]. Long-term use
of antimicrobial regimens is a common practice in elderlycare
settings, and it is estimated that between four and
seven antibiotic prescriptions are written per 1,000 resident
days in long-term care facilities [30]. Half of all hospitalized
patients are treated with antibiotics [31], and ADRs
have been reported to occur in 10–20 % of these patients
[32]. Furthermore, nephrotoxicity is the most frequent
severe ADR in patients using antibiotics [33].
2.2 Drug–Drug Interactions
Combinations of medications can lead to altered pharmacokinetics
and greater risk of toxicity [34]. Although the