Final answer:
The most important instruction is to complete the full 10-day course of amoxicillin to prevent antibiotic resistance and ensure the infection is fully eradicated.
Step-by-step explanation:
The instruction most important for the nurse to review with the parents of a 1-year-old diagnosed with acute otitis media (AOM) and prescribed a 10-day course of amoxicillin is to ensure the full course of antibiotics is completed. This is crucial because not completing the full course can result in antibiotic resistance and can fail to fully eradicate the infection. Parents should also be informed of potential side effects and what to do in case the child does not show improvement. Educating parents about the importance of the entire treatment regimen will help prevent the spread of drug-resistant bacteria and ensure the best chance for a full recovery.