The pharmacokinetics of uniphyllin in nocturnal asthma

Controlled-release theophylline in the treatment of nocturnal asthma

A total of 104 asthmatic patients with symptoms of asthma and/or a 'morning dip' in the peak expiratory flow rate (PEFR) who were receiving multiple therapies, including inhaled or oral steroids, were treated in addition once nightly with controlled-release theophylline in an 8-week double-blind, placebo-controlled cross-over study. Theophylline produced an improvement in symptoms of cough, wheeze, sleep disturbance and PEFR in the 73 completing patients compared to run-in and placebo treatment. Theophylline also produced an improvement in the forced expiratory volume in 1 s and forced vital capacity relative to baseline, and in the difference between actual and predicted PEFR values. Nausea was the most frequent side-effect but both patients' and investigator's global impressions of the effect of study medication were in favour of theophylline.

Validation of morning dip of peak expiratory flow as an indicator of the severity of nocturnal asthma

Overnight falls in peak expiratory flow (PEF) (with the morning dip of the index) may be considered the hallmark of nocturnal asthma. To validate the morning dip a quantitative marker of the degree of nocturnal bronchoconstriction, the dip was measured in 11 subjects (six with a history consistent with nocturnal asthma) undergoing all-night monitoring of lower respiratory resistance by a double-catheter method. In six subjects, marked and recurrent increases in resistance were recorded, along with morning dips higher than 20 percent; however, on the following morning, only two of them reported having suffered significant breathlessness and wheeze. Peak and average values for resistance, as well as the duration for which resistance was increased, were closely correlated with the magnitude of morning dips. Therefore, unlike the subjective report, PEF may be considered a reliable quantitative indicator of nocturnal bronchoconstriction.

The accuracy of a pharmacokinetic theophylline predictor using once daily dosing

1. The accuracy of a computer based pharmacokinetic prediction method based on Bayesian analysis has been evaluated for an oral show release form of theophylline. 2. In 83 patients from seven centres 24 h serum theophylline concentration-time profiles were measured under a variety of circumstances. 3. Revised predictions of 24 h serum theophylline concentration profiles were generated by Bayesian analysis using single serum drug concentrations taken before, during and after the study days in different subgroups of those patients. Comparing the predicted and measured profiles the mean prediction error (bias) was 0.05 mg l-1 for peak concentrations and 0.04 mg l-1 for trough concentrations during once daily dosing. The corresponding root mean squared prediction errors (precision) were 2.59 and 1.17 mg l-1, respectively. 4. This accuracy is considered more than adequate for clinical purposes. 5. The technique can be used with a variety of other drugs and can form a valuable part of a routine therapeutic drug monitoring service.