Antibiotics at the extremes of age: choices and constraints.

Infection is a frequent cause of morbidity and mortality at the extremes of life. Its treatment is complicated by a lack of specificity in the clinical findings and wider range of pathogens than in other patients. For these reasons empirical therapy must cover a wide range of pathogens and yet, because the clinical findings may not even be due to infection, it should be as non-toxic as possible. It is also essential to investigate intensely before therapy so as to stand the best chance of making an aetiological diagnosis and possibly allowing a change to more directed therapy. Neonates in particular, but also the elderly, are susceptible to age-associated antibiotic toxicities, such as those from tetracyclines and chloramphenicol. Polypharmacy in the elderly renders them particularly liable to drug interactions. Both age groups have altered pharmacokinetics of antibiotics, including differences in absorption, distribution and elimination compared with healthy adults, and therapeutic drug monitoring may be needed more frequently as a result.