theophylline molecule 3d, molecular structure, ball and stick model, structural chemical formula 1,3-dimethylxanthine

theophylline 13dimethylxanthine inhibits phosphodiesterase adenosine receptors chronic obstructive pulmonary disease copd asthma molecule molecular structure chemical formula 3d model c7h8n4o2 atom chemistry science laboratory medicine drug biology medication research atomic drawing skeletal substance element organic education oxygen scientific composition structural compound hydrogen technology alkaloid purine bond futuristic medical pharmaceutical hormone stimulant