Serum/saliva correlations for theophylline in asthmatics

Area of Science:

• Pharmacology and Therapeutics
• Clinical Chemistry
• Respiratory Medicine

Background:

• Theophylline is a bronchodilator commonly prescribed for asthma management.
• Therapeutic drug monitoring of theophylline is crucial due to its narrow therapeutic index.
• Traditional monitoring involves serum level measurements, which are invasive.

Purpose of the Study:

• To compare theophylline levels in mixed saliva (stimulated and unstimulated) with serum levels.
• To evaluate the accuracy of saliva theophylline levels in predicting total and free (unbound) serum concentrations.
• To establish the reliability of saliva as a non-invasive monitoring tool for theophylline.

Main Methods:

• Collected stimulated and unstimulated mixed saliva samples from 28 asthmatic outpatients on regular theophylline therapy.
• Measured theophylline concentrations in saliva and compared them with simultaneously measured total and free serum theophylline levels.
• Assessed the predictive accuracy of saliva theophylline levels for serum concentrations.

Main Results:

• Stimulated saliva accurately predicted unbound serum theophylline concentrations in 92.9% of samples within +/- 1 microgram/mL.
• Total serum theophylline levels reliably predicted unbound serum concentrations in 100% of cases within +/- 1 mg/L.
• Saliva theophylline levels demonstrated higher accuracy and precision in predicting unbound serum levels compared to total serum levels.

Conclusions:

• Mixed stimulated saliva is a reliable, non-invasive method for monitoring unbound serum theophylline levels in asthmatic patients.
• The established therapeutic range for saliva theophylline is approximately 5.6-11.3 mg/L, corresponding to serum levels of 10-20 mg/L.
• This approach offers a practical alternative to serum monitoring, potentially improving patient compliance and convenience.