Diet-induced changes in trough theophylline concentrations in an elderly asthmatic patient

A 66-year old obese man with asthma was given a hypocaloric (1100 Kcal) and low protein (35 g) diet for nine days. While receiving theophylline (Theodur), 200 mg bid, his morning trough theophylline concentrations rose from 3.40 micrograms/ml to 12.7 micrograms/ml by day 9 of this diet. Following discontinuation, his theophylline concentration fell to 5.95 micrograms/ml by day 6 on home diet. The patient lost 3.67 kg during the nine-day study. Thus, a brief exposure to a hypocaloric, low protein diet in this elderly patient with asthma caused a dramatic rise in trough theophylline concentrations.