A common adverse effect of methylxanthines at therapeutic levels is?

A common adverse effect of methylxanthines at therapeutic levels is?

• A. Hypotension
• B. Tachycardia
• C. Hypoglycemia
• D. Tremor

Answer: (B)

Methylxanthines, like theophylline, have stimulant effects on the heart. They inhibit phosphodiesterase and block adenosine receptors, which raises intracellular cAMP and enhances sympathetic activity. This combination tends to speed up the heart and can cause tachycardia even at therapeutic doses. While tremor and other CNS stimulation can occur, the heart-rate increase is a common and characteristic adverse effect at usual dosing. Hypotension and hypoglycemia aren’t typical effects of therapeutic methylxanthine use.

Methylxanthines, like theophylline, have stimulant effects on the heart. They inhibit phosphodiesterase and block adenosine receptors, which raises intracellular cAMP and enhances sympathetic activity. This combination tends to speed up the heart and can cause tachycardia even at therapeutic doses. While tremor and other CNS stimulation can occur, the heart-rate increase is a common and characteristic adverse effect at usual dosing. Hypotension and hypoglycemia aren’t typical effects of therapeutic methylxanthine use.