Impact of therapeutic drug monitoring of intravenous theophylline regimens on serum theophylline concentrations in the medical intensive care unit

OBJECTIVE: The primary objective of this study was to determine if a clinical pharmacist ensuring appropriate use and performing careful pharmacokinetic analysis of serum theophylline concentrations (STCs) can result in optimal theophylline regimens for patients in a medical intensive care unit (ICU). DESIGN: In phase 1 of the study, housestaff physicians determined the theophylline dosing regimen. A clinical pharmacist prospectively followed these initial patients, but did not intervene. Patients in phase 2 received intravenous theophylline, with all dosing regimens being based on prospective therapeutic drug monitoring (TDM) by a clinical pharmacist. PARTICIPANTS: The first phase enrolled 11 consecutive patients admitted into the medical ICU and requiring intravenous theophylline. This was followed by a second phase of 14 medical ICU patients whose intravenous theophylline regimen was determined by a clinical pharmacist performing pharmacokinetic analysis. MAIN OUTCOME MEASURES: Questions were organized into the following sections: (1) number of STC blood samples drawn, (2) number of emergency STCs performed, (3) number of concentrations per infusion-rate changes, (4) number of STC results in the pharmacist-generated regimens that were within the physicians' predetermined acceptable range. RESULTS: In phase 1, 27 theophylline rate changes occurred, with a mean +/- SD of 1.01 +/- 0.3 STCs per day. In phase 2, 44 theophylline infusion rates were changed, with a mean +/- SD of 0.62 +/- 0.3 STCs per day. The TDM group had a significant reduction (p less than 0.001) in inappropriate concentrations (15 vs. 40 percent) as set by predetermined criteria, and fewer emergency theophylline concentration requests (2 vs. 14). Serum theophylline concentrations ordered by the physician were achieved in 85 percent of the pharmacist-generated regimens. CONCLUSIONS: Pharmacokinetic analysis when performing TDM in the determination of intravenous theophylline regimens can result in optimal therapy for patients, while significantly reducing the number of STCs required.