xantic bases
Derivatives of xanthine, known collectively as xanthines, are a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma.
In contrast to other, more potent stimulants, they only inhibit the actions of sleepiness-inducing adenosine, making them somewhat less effective as stimulants than sympathomimetic amines.
Due to widespread effects, the therapeutic range of xanthines is narrow, making them merely a second-line asthma treatment. The therapeutic level is 10-20 micrograms/mL blood; signs of toxicity include tremor, nausea, nervousness, and tachycardia/arrhythmia.
Methylated xanthine derivatives include caffeine, paraxanthine, theophylline, and theobromine. These drugs inhibit phosphodiesterase and antagonise adenosine.
Xanthines are also found very rarely as constituents of nucleic acids.