Final answer:
The appropriate initial pharmacologic intervention for an 18-year-old patient with maxillary facial pain and yellow nasal discharge is the use of antibiotics, specifically amoxicillin or amoxicillin-clavulanate.
Step-by-step explanation:
The appropriate initial pharmacologic intervention for an 18-year-old patient presenting with maxillary facial pain and yellow nasal discharge for 14 days would be the use of antibiotics. These symptoms are suggestive of a sinus infection. Since the presentation is not severe and the patient is otherwise healthy, a typical first-line antibiotic for sinus infections, such as amoxicillin or amoxicillin-clavulanate, would be an appropriate choice.
It's important to note that the prescription of antibiotics should be done by a qualified healthcare professional after a proper evaluation of the patient.