A 41-year-old male presents with fever for 2 weeks and right upper quadrant and right flank pain for 1 week. Physical exam: bulging right upper quadrant, liver 3 cm below the costal margin with tenderness on percussion and palpation. Ultrasound shows a 5 cm × 4 cm fluid level in the lower part of the right lobe of the liver. History of chronic diarrhea 1 month ago. Diagnosis: amoebic liver abscess. Which of the following treatments is incorrect?