Theophylline-d₆is intended for use as an internal standard for the quantification of theophylline by GC- or LC-MS. Theophylline is an inhibitor of phosphodiesterase (PDE; K_i= 100 µM).¹It is also an adenosine A₁and A₂receptor antagonist (K_i= 14 µM for both).²Theophylline induces relaxation of isolated cat bronchial smooth muscle segments precontracted with acetylcholine (EC₄₀= 117 µM).³It inhibits ovalbumin-induced increases in bronchoalveolar lavage fluid (BALF) eosinophil infiltration in an ovalbumin-sensitized mouse model of allergic asthma. Formulations containing theophylline have been used in the treatment of asthma and chronic obstructive pulmonary disease (COPD).

1.Butcher, R.W., and Sutherland, E.W.Adenosine 3',5'-phosphate in biological materials. I. Purification and properties of cyclic 3',5'-nucleotide phosphodiesterase and use of this enzyme to characterize adenosine 3',5'-phosphate in human urineJ. Biol. Chem.237(4)1244-1250(1962) 2.Daly, J.W., Padgett, W., Shamim, M.T., et al.1,3-Dialkyl-8-(p-sulfophenyl)xanthines: Potent water-soluble antagonists for A1- and A2-adenosine receptorsJ. Med. Chem.28(4)487-492(1985) 3.Leemans, J., Kirschvink, N., and Gustin, P.A comparison of in vitro relaxant responses to ipratropium bromide, β-adrenoceptor agonists and theophylline in feline bronchial smooth muscleVet. J.193(1)228-233(2012)