What is the most appropriate action for a patient with moderate persistent asthma who has a personal best peak flow of 600 L/min but has dropped to 540 L/min?

For a patient with moderate persistent asthma experiencing a decrease in peak flow from 600 L/min to 540 L/min, maintaining the current drug therapy as the most appropriate action is justified. A drop in peak flow can indicate a worsening condition; however, the patient's current peak flow rate remains within 80% of their personal best, which is typically an indicator of effective asthma control.

In this situation, a careful assessment of the patient's symptoms, triggering factors, or adherence to the current medication regimen is warranted before making changes to the treatment plan. Adjustments to medication are generally considered when the peak flow drops below 80% of the personal best, which would indicate the need for an intervention rather than maintaining the current strategy.

Changes like increasing the dosage of inhaled corticosteroids, adding a long-acting beta-agonist, or switching medications may be unnecessary at this moment, especially without further evidence of more significant airflow obstruction or symptomatic exacerbation, as these would be more appropriate for situations where the patient's peak flow indicates a more critical concern for control of the asthma. In this case, monitoring the patient's condition and encouraging them to avoid triggers would be more suitable before contemplating any changes to their medication regimen.