Which effect is associated with theophylline?

• A. CNS stimulation
• B. Tachycardia
• C. Dilation of pulmonary blood vessels
• D. Sedation

Answer: (A)

Theophylline is a methylxanthine, and its most characteristic effect among these options is stimulation of the central nervous system. This occurs because it blocks adenosine receptors in the brain, removing adenosine’s calming, sleep-promoting influence and leading to increased alertness, tremor, and, at higher levels, seizures. The drug also inhibits phosphodiesterase, raising cAMP in bronchial smooth muscle to promote bronchodilation, which is why it helps with asthma or COPD. Tachycardia can occur as a systemic stimulant effect, but CNS stimulation is the defining association. Sedation is not typical, and dilation of pulmonary blood vessels is not the primary effect of theophylline.