1. Any of a class of alkaloid compounds derived from xanthine and containing a methyl group, including caffeine, theobromine, and theophylline, commonly found in plants and used as stimulants or in medicine.
Usage: technical; chemistry/pharmacology

Examples

• Caffeine is the most well-known methylxanthine found in coffee and tea.
• Methylxanthines are used in some asthma medications to help open airways.
• Theobromine, a methylxanthine in chocolate, has mild stimulant effects.
• The pharmacist explained that methylxanthines work by blocking adenosine receptors in the brain.
• Theophylline, another methylxanthine, was historically used to treat respiratory conditions.