Adverse Reactions Adverse drug reactions are frequently classified by mechanism as either dose-related ("toxic") or unpredictable. Unpredictable reactions are either idiosyncratic or allergic. Dose-related reactions include aminoglycoside-induced nephrotoxicity, linezolid-induced thrombocytopenia, penicillin-induced seizures, and vancomycin-induced anaphylactoid reactions. Many of these reactions can be avoided by reducing dosage in patients with impaired renal function, limiting the duration of therapy, or reducing the rate of administration. Adverse reactions to antibacterial agents are a common cause of morbidity, requiring alteration in therapy and additional expense, and they occasionally result in death. The elderly, often those with the more severe infections, may be especially prone.
