Clinical audit of theophylline use in general practice.

The use of therapeutic drug monitoring for theophylline therapy was evaluated in two urban general practices. Of 55 patients studied, 44 (80%) had a sub-therapeutic serum theophylline concentration, 11 (20%) had a therapeutic concentration (10-20 micrograms/ml), and none had an above therapeutic concentration. Patients were reviewed at weekly intervals and had their theophylline dosages adjusted according to serum levels. A therapeutic concentration was achieved in 37 patients (67%). This task proved to be 'laborious but not difficult'. Side-effects were less common than previous reports suggest. The general practice workload involved in adjusting theophylline dosage was approximately four consultations, one dose change and two serum assays per 'average' patient.