Theophylline Unit Conversion

Theophylline (1,3‑dimethylxanthine), a bronchodilator, is widely used to treat patients with asthma, apnea (temporary asphyxia), and other obstructive lung diseases. Monitoring of theophylline concentrations in serum is essential, since individuals can vary in their rates of theophylline clearance, and severe toxicity has been observed without prior occurrence of minor side effects. Moreover, several factors can alter theophylline elimination. Theophylline elimination is slowed in obese patients, patients with hepatic disease, and in those on a high carbohydrate, low protein diet. Premature infants have very low rates of theophylline elimination. Conversely, theophylline elimination is more rapid among cigarette smokers. In combination with other clinical data, monitoring serum theophylline levels may provide the physician with useful information to aid in adjusting patient dosage to achieve optimal therapeutic effect while avoiding drug toxicity.

Various methodologies have been used to evaluate theophylline preparations and routes of administration, to study pharmacokinetics of the drug, and to define the relationship between serum concentration and the drug’s therapeutic and toxic effects. For most patients, the range of 10 to 20 μg/mL (55.5 to 111 μmol/L) suppresses chronic asthmatic symptoms. Wide discrepancies between drug dosage and serum concentrations were observed among patients receiving identical doses. A major factor accounting for the variability is individual variation in the rate of theophylline metabolism and elimination.