The disposition of theophylline in camels after intravenous administration

The pharmacokinetics of theophylline were determined after an intravenous (i.v.) dose of 2.36 mg/kg in six camels and 4.72 mg/kg body weight in three camels. The data obtained (median and range) for the Low and high dose. respectively, were as follows: the distribution half-lives (t(1/2α)) were 1.37 (0.64-3.25) and 2.66 (0.83-3.5) h, the elimination half-lives (t(1/2β)) were 11.8 (8.25-14.9) and 10.4 (10.0-13.5) h, the steady state volumes of distribution (V(ss)) were 0.88 (0.62-1.54) and 0-76 (0.63-0.76) L/kg, volumes of the central compartment (V(c)) were 0.41 (0.35-0.63) and 0.51 (0.36-0.52) L/kg, total body clearances (Cl(t)) were 62.3 (39.4-97.0) and 50.2 (47.7-67.4) mL/h.kg body weight and renal clearance (V(r)) for the low dose was 0.6 (0.42-0.96) mL/h.kg body weight. There was no significant difference in the pharmacokinetic parameters between the two doses. Theophylline protein binding at a concentration of 5 μg/mL was 32.2 ± 3.3%. Caffeine was identified as a theophylline metabolite but its concentration in serum and urine was small. Based on the pharmacokinetic values obtained in this study, a dosage of 7.5 mg/ kg body weight administered by i.v. injection at 12 h intervals can be recommended. This dosing regimen should achieve an average steady state serum concentration of 10 μg/mL with peak serum concentration not exceeding 15 μg/mL.