For a PK/PD antibiotic where efficacy correlates with AUC/MIC, if the current dosing yields suboptimal AUC/MIC, which strategy would likely improve efficacy?

• A. Increase dose.
• B. Shorten the dosing interval only.
• C. Increase dose, decrease interval, or increase dosing frequency.
• D. Switch to a different antibiotic without adjusting dosing.

Answer: (C)

The key idea is that your antibiotic’s efficacy here is driven by exposure relative to the MIC, quantified as the AUC/MIC. To boost cure chances, you need to increase the drug exposure over a 24-hour period. The total daily exposure (AUC over 24 hours) grows when you raise the daily dose, because AUC is proportional to the amount of drug reaching the body each day.

If you increase the per-dose amount, you raise the daily exposure directly. If you shorten the dosing interval, you’re delivering more drug per day (assuming you compensate so the total daily dose goes up or remains sufficiently high), which also raises the 24-hour AUC and thus AUC/MIC. Increasing how often you administer the drug can have the same effect, again by increasing the total daily exposure, while keeping safety in mind.

Swapping to a different antibiotic would not optimize the current agent’s AUC/MIC target, unless you also adjust dosing to match its PK/PD properties.

So, increasing dose, shortening interval, or increasing dosing frequency all aim to raise 24-hour exposure relative to MIC, which is why that approach would likely improve efficacy.