mrcem2-1725

A 32-year-old patient with a known history of asthma presents with a worsening of his asthma symptoms. He typically uses a salbutamol inhaler, beclomethasone inhaler, and theophylline. However, his theophylline levels are currently below the therapeutic range. It seems that a newly prescribed medication may be causing a decrease in his theophylline levels.
Which of the following drugs is most likely causing this interaction?