Why antibiotic dosing should be tailored to patients’ physical characteristics

Originally published in Insidermedicine

The dosing of antimicrobial agents should be tailored to patients’ physical characteristics in order to achieve maximal effectiveness and safety, according to a Viewpoint argument made in the The Lancet.

Here are some guidelines for the use of antibiotics in adults from the Singapore Ministry of Health:

• Antibiotics should be used only for treatment of patients with confirmed or suspected bacterial infections.

• Antibiotics may be used for prophylaxis where consequences of infection would be severe.

• Clearly instruct patients or their caregivers on the dose and the necessity of finishing a course of treatment.

Researchers out of the Alfa Institute of Biomedical Sciences in Athens provided many compelling reasons why antimicrobial agents should be dosed based on patients’ individual physical characteristics. Physicians treat adults whose body weight and composition vary dramatically from one another, and there is good evidence that the metabolism and clearance of some antimicrobial drugs can be substantially affected by these factors. At the same time, the growing threat of drug-resistant pathogens calls for a need to maximize the effectiveness of currently available antimicrobial agents.

Antimicrobials most in need of individualized dosing include those with a narrow therapeutic window, such as aminoglycosides, daptomycin, colistin, and amphotericin B, as well as those that are given at high doses for specific indications, including co-trimoxazole, metronidazole, and acyclovir. An unresolved issue for the proper dosing of most antimicrobial agents, however, is which body size descriptor to use in order to determine dose. Possibilities include total, adjusted, ideal or lean bodyweight, body surface area, and body mass index.

Today’s research indicates that a move toward individualizing the dosing of antimicrobial agents is warranted.