You are seeing 22-month-old Luca, who is brought into the office with two concerns.

His mother says he has been scratching a small spot on his left arm for about 3-4 weeks. She thinks it is getting a little larger. He has not had any exposure to new food, medications, lotions, or soaps. He has no known allergies to food or medications.

The mother says she had the appointment scheduled about a week ago, and for the last four days, he has been complaining of "ear hurt" and pulling at his right ear. She is thankful she already had the appointment for the "spot," as it looks like he has two problems.

Luca attends "Mum’s Day Out" at the church 2-3 times a week from 10 a.m. to 3 p.m. and enjoys it. His mother does not think any other child at the daycare has been ill with a febrile illness or any skin rashes.

Luca has had all recommended immunizations. The mother has treated the spot on his arm only with Neosporin, which did not help, and has not used anything else on it in the last 72 hours.

Regarding the ear pain, his mother says he has not been eating well for the last day or so and vomited once last night. She has not checked his temperature at home.

Luca lives at home with his parents, a 10-year-old sister, and a 4-year-old Maine Coon cat. His mother does not work outside the home; his father owns a technology company. No one at home is ill or has any skin problems.

On exam today, you see a well-nourished Caucasian male.

Vital signs:
- Temperature: 39°C
- Pulse: 105
- Respirations: 26
- Blood Pressure: 90/50
- Height: 34 inches
- Weight: 27 pounds

Luca’s skin is warm and dry; the only lesion is on his left forearm, the size of a quarter. It has a red, raised border with active scaling at the borders and central clearing.

Luca is active in the exam room but begins to cry as you start to check his ears. On exam, the left ear is normal, but the right ear shows slight injection in the external canal, and the tympanic membrane is slightly dull but otherwise unremarkable. The nares are slightly red and swollen with no exudate. He really begins to cry when you look at his throat—both tonsils are swollen, and there are white patches on the back of the throat. There are palpable submental and anterior cervical lymph nodes. The lungs are clear with no increased work of breathing. No other abnormalities are noted on Luca’s exam.

1. What drug and drug class would be the best choice in this scenario? State the name of the drug and its mechanism of action. If there is information from the patient’s history or exam that was important in choosing the agent (patient-specific factors), cite those.

For Luca's skin lesion, an antifungal medication such as terbinafine is suitable, and for his ear and throat symptoms, an antibiotic like amoxicillin may be necessary to treat the suspected bacterial infection.

Antifungal medication is the best choice in this scenario for treating the skin lesion. The description of the lesion as a red, raised border with active scale and central clearing is characteristic of a fungal infection, commonly known as ringworm. An appropriate choice of medication could be terbinafine, which belongs to the allylamine class of antifungal drugs. Terbinafine works by inhibiting the enzyme squalene epoxidase, which is part of the ergosterol synthesis pathway in fungi. This disruption in the pathway results in a deficiency of ergosterol, which is a vital component of fungal cell membranes, leading to cell death.

For Luca's ear pain and possible throat infection, his symptoms of fever, vomiting, and swelling and redness in the throat, including white patches, suggest a bacterial infection. Therefore, antibiotics may be warranted for Luca's condition. Given the symptoms and physical examination findings, an antibiotic like amoxicillin, which is a penicillin antibiotic, might be indicated. It functions by inhibiting the synthesis of bacterial cell walls, leading to bacterial cell death. Luca's lack of known drug allergies and his clinical presentation make amoxicillin a reasonable first choice, typically prescribed for conditions such as otitis media and streptococcal pharyngitis.