A 47-year-old office worker presents with sharp, pleuritic central chest pain that improves when he sits forward. He had a viral upper respiratory illness 1 week ago. Examination shows a low-grade fever and a pericardial friction rub. ECG demonstrates widespread concave ST elevation with PR depression. Troponin is normal and echocardiography shows a small pericardial effusion without tamponade. What is the most appropriate initial outpatient pharmacological management?