A prospective trial using salivary‐theophylline levels to guide asthma therapy

In three prospectively designed studies, first saliva (SA) samples were collected simultaneously with serum (SE) from 86 children who received slow‐release theophylline (Th) bid. for treatment of bronchial asthma. SA was collected with a standardized sampling procedure. Regression analysis revealed a close correlation between SE and SA–Th levels (r=0.959; SE=1.87 × SA + 0.05) and yielded a “therapeutic SA–Th range” of 5.8 to 10.7 mg/L. In 16 children the diurnal variation was then assessed by measuring 6 SA–Th levels within 24 hr, using the same sampling method. At 0, 9, and 24 hr SE–Th levels were also measured. The levels of SE–Th and SA–Th were again closely correlated (0.914 ≤ r ≤ 0.949) and both remained constant over the 24‐hr period. In the third prospective trial only SA levels were used to monitor Th therapy in 50 asthmatic children. Seven days after starting therapy SA‐Th levels were measured and then the Th dose was increased weekly until SA‐Th levels above 5.8 mg/L were reached. The following day SE and SA samples were collected simultaneously and their Th levels compared. In 36 of the 47 children who completed the study therapeutic SE‐Th levels (≥10 and ≤20 mg/L) were measured; in one patient it was 320 mg/L, in 6 it was between 8.0 and 10 mg/L, and only 4 had SE levels <8.0 mg/L. There were no potentially toxic SE‐Th levels that were not reflected by increased SA levels. From these prospective studies we conclude that SA‐Th levels can be used to guide Th therapy in children with asthma. © 1992 Wiley‐Liss, Inc.