xanthine

• Xanthine

  A purine base found in most human body tissues and fluids and in other organisms
• Xanthine

  • A number of mild stimulants are derived from it, including caffeine and theobromine
  • It is a product on the pathway of purine degradation
• Xanthine formation

  1. Created from guanine by guanine deaminase

  2. Created from hypoxanthine by xanthine oxidoreductase

  3. Converted to uric acid by xanthine oxidase enzyme
• People with the rare genetic disorder xanthinuria lack sufficient xanthine oxidase and cannot convert xanthine to uric acid
• Xanthines

  Derivatives of xanthine, a group of alkaloids commonly used for their effects as mild stimulants and as bronchodilators, notably in treating the symptoms of asthma
• Xanthines

  • Only inhibit the actions of sleepiness-inducing adenosine, making them somewhat less effective as stimulants than sympathomimetic amines
  • Therapeutic range is narrow, making them merely a second-line asthma treatment
  • Therapeutic level is 10-20 micrograms/mL blood; signs of toxicity include tremor, nausea, nervousness, and tachycardia/arrhythmia
• Herbs containing methylxanthines

  • Theophylline
  • Caffeine
  • Theobromine
• Methylxanthines

  • Have several pharmacological actions including CNS stimulation, relaxation of smooth muscle (especially bronchial muscle), myocardial stimulation, peripheral vasoconstriction and diuresis
  • Infrequently used by herbalists as mild stimulants; widespread consumption of tea and coffee beverages is the most common mode of consumption
  • Frequently added to "natural" energy-boosting products, occasionally with misleading labels such as "caffeine free"
• Mechanism of action of xanthines

  Not fully understood but thought to involve several factors including adenosine receptor antagonism, modulation of intracellular calcium, phosphodiesterase inhibition, with central, vagal vasomotor and respiratory center actions
• Xanthine toxicity

  • Low, side effects include insomnia, anxiety, restlessness, tachycardia and extrasystoles and tachypnea