Theophylline is metabolized mainly by Cyp1A2, and also by Cyp2E1 and Cyp 3A4. Extensive drug interaction studies have not given evidence of significant capacity for Cyp-induction or irreversible Cyp-inhibition. There are probably no significant porphyrogenic physiological effects or side effects.

Theophylline is a dimethyl purine (dimethylxanthine).

Theophylline is used in the treatment of bronchial asthma and emphysema with bronchial obstruction. It can be administered orally or intravenously. The main effect of theophylline is to relax airway smooth muscle, but there are also anti-inflammatory effects active via at least two different mechanisms. Like other xanthines, theophylline acts as a coronary vasodilator, diuretic, cardiac stimulant, cerebral stimulant and skeletal muscle stimulant. Physiological effects and side effects of possible relevance to acute porphyria: The anti-inflammatory effects theophylline is probably mediated via inhibition of the nuclear translocation of NF-kB, thus reducing the expression of inflammatory genes. Theophylline also activates histone deacetylases that reverse intrinsic acetyltransferase activity, which otherwise increase Nf-kb activation. As an effect, the extent of NF-kB inhibition of PXR in inflammation may be reduced. Common adverse reactions of theophylline that can be confused with an acute porphyric attack are nausea, vomiting, irritability, nervousness and insomnia.

Theophylline is metabolized to1,3-dimethyluric acid , 1-methyluric acid and 3-methylxanthine . Demethylation to 3-methylxanthine is catalyzed by the cytochrome P450 isoenzyme CYP1A2; hydroxylation to 1, 3-dimethyluric acid is catalyzed by CYP2E1 and CYP3A3. Listed as a weak inhibitor of CYP 1A2. Several drugs are observed to accelerate or retard the elimination of theophylline. In contrast there are no observations of theophylline affecting the Cyp-metabolism of other drugs in clinical use. Nor are there any reports or references to in vitro capacity of theophylline for significant Cyp inhibition or induction, with the possible exception of Cyp1A2 inhibition.

Kaupppinen 1992: Reported to be tolerated (n=2).

Uneventful use reported in 1 patient with acute porphyria.