Methylxanthines

Methylxanthines are purine derivatives that are produced biosynthetically by enzymatic methylation of free xanthine at N-1,N-3 and/or N-7. Naturally occurring methylxanthines are caffeine, theobromine and theophylline. They are used as medicines in various areas.

Methylxanthines have, among other things, central stimulating effects; they have a dilating effect on skin and blood vessels. They also have a bronchodilatory and diuretic effect. They exert their effect by inhibiting adenosine receptors (ATP receptors). In higher doses, methylxanthines act as non-selective phosphodiesterase inhibitors.

The following substances belong to the methylxanthines (see structural formulas):

• theophylline
• theobromine
• caffeine

Another methylxanthine used therapeutically is aminophylline, a complex of theophylline and ethylenediamine.