[Comparative study of sustained-release in theophylline (Slobid, Theolong, Theodur) by pharmacokinetics]

We made a comparative study of three kinds of sustained-release of theophylline compounds by means of analysis of plasma concentrations. The drugs were Slobid (SB) (Up-john) 11 patients (10 men, 1 women), Theolong (TL) (Eisai) 22 (10 men, 12 women), Theodur (TD) (Nikken chemicals) 34 (18 men, 16 women), who were hospitalized from January 1989 to November 1994. Theses patients were given oral theophylline, bid at 9:00 and 21:00, plasma concentration of theophylline was determined at 9:00, 12:00, 15:00, 18:00 and 21:00, after plasma concentration reached a plateau. There were no significant differences as to the zero absorption rate, clearance, the moment absorption rate, but there were significant differences to Cmax-Cmin of SB (3.34 micrograms) < TL (4.22) < TD (5.22) (P = 0.0150), the zero half life time (T1/2) of SB (18.9 hr) > TL (13.5) > TD (10.1) (P = 0.0061), the apparent distribution volume (V) of SB (0.811/ kg) > TL (0.78) > TD (0.55) (P = 0.0309), mean residence time (MRT) of SB (21.3 hr) > TL (16.7) > TD (15.2) (P = 0.0034), the moment half life time (Tm1/2) of SB (13.7 hr) > TL (10.6) > TD (9.55) (P = 0.009), by measurements analysis of variance. These results suggest that these sustained-release drugs have different pharmacokinetics judging from the important indices including Cmax-Cmin, T1/2, V, MRT and Tm1/2, and that the best one is the SB, the second is the TL, and the third is the TD for RTC therapy.