Bioequivalence of sustained release theophylline formulations
The bioequivalence of sustained release theophylline formulations, marketed in the United Kingdom, has been investigated in relation to the co-administration of food in both single dose and steady state volunteer studies. The effect of food on pharmacokinetic parameters and their clinical relevance was researched. Experimentation using drug induced modification of gastric motility to ascertain the component influences of the rate of gastric emptying on the absorption of theophylline from sustained release formulations was conducted. Prolongation of time to maximum plasma theophylline concentration by food reported in the literature and its clinical importance was investigated in once daily compared with twice daily administration of sustained release theophylline formulations and smoking habit. The correlation between saliva and plasma theophylline concentrations as a means of developing a non-invasive sampling techniques was examined. Data obtained from in vitro dissolution studies was compared with in vivo results. This thesis has shown no significant differences occurred in the pharmacokinetic parameters measured between sustained release formulations available in the United Kingdom. The investigations into the influence of food on prolongation of time to maximum plasma theophylline concentration and other measured pharmacokinetic parameters demonstrated no important pharmacokinetic or clinical effects. Smoking adults taking sustained release theophylline formulations had similar drug clearances to those reported in the literature for smokers taking plain uncoated theophylline formulations.