Study on the effect of food on the absorption of theophylline.
BACKGROUND
The pharmacokinetics of theophylline under fasting and normal meal have been widely studied, but that of Euphyllin Retard in Chinese subjects has not been reported. Since various food-induced absorption changes occur with sustained-release theophylline, it is of interest to study the food effect (especially Chinese food) on this drug product.


METHODS
A total of 10 non-smoking healthy male volunteers were involved in the study with a 2-period crossover comparison. They were randomly divided into 2 groups. In the first phase study, group A took a single dose of 350 mg Euphyllin Retard (theophylline-ethylenediamine formulation, containing 255 anhydrous theophylline) under fasting condition. Group B took the same dose with breakfast. Blood samples were collected before and during the 36 hours following administration of the drug. For the second-phase study after 2 weeks, the group A acted as fasting group and group B as non-fasting group. The difference in the absorption of theophylline with fasting versus non-fasting administration was assessed using pharmacokinetic parameters derived from a serum theophylline concentration (STC) vs time curve.


RESULTS
The means of maximum drug concentration (Cmax), unextrapolated area under the concentration vs time curve (AUC) from time 0 to 24 hours (AUCun), extrapolated AUC from time 0 to infinity (AUCex), and terminal elimination rate constant (Kel) were higher in the non-fasting group. The fasting group showed a more delayed time to maximum concentration (Tmax). The mean of half-life (T50%) was slightly higher in fasting group. In comparing each of the variables, no statistically significant differences were demonstrated between the 2 modes of administration except Cmax.


CONCLUSIONS
Food increases the rate but not the extent of the absorption of Euphyllin Retard, and one should be aware of the possibility of unwanted side effects caused by high peak concentration. There were wide variations in serum drug levels among individuals, so serum theophylline level monitoring is necessary for an optimal effect. This study was performed in a limited number of normal healthy subjects and the same result is yet to be in asthmatic patients and a larger population of normal subjects.
Su
Yih-Ming
YM
Division of Chest Medicine, Department of Internal Medicine, Far-Eastern Memorial Hospital, Panchiao, Taipei, Taiwan, ROC. yihming@ms18.hinet.net
Cheng
Tien-Pao
TP
Wen
Cheng-Yu
CY
D000328:Adult; D000628:Aminophylline / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations; D004435:Eating; D005502:Food; D006207:Half-Life; D006801:Humans; D008297:Male; D013806:Theophylline / Q000097:blood
D003692:Delayed-Action Preparations; D000628:Aminophylline; D013806:Theophylline