Study Objective. To evaluate the disposition of pentoxifylline and its metabolite, lisofylline, in New Zealand rabbits after two alternative routes of administration, intranasal and intratracheal. Design. Pharmacokinetics study in an animal model. Setting. University-affiliated animal care facility. Subjects. Twenty New Zealand white rabbits divided into four groups of five rabbits each: group 1 did not receive study drug (control group), and groups 2, 3, and 4 evaluated intravenous, intranasal, and intratracheal routes of administration, respectively. Intervention. Each rabbit in groups 2-4 received pentoxifylline as a single 20-mg/kg dose by their respective route of administration. Measurements and Main Results. Blood samples were collected over a 24-hour period and were analyzed by using high-performance liquid chromatography-tandem mass spectrometry. The pharmacokinetic parameters evaluated were area under the concentration-time curve from time zero extrapolated to infinity (AUC 0-∞), maximum concentration (Cmax), time to maximum concentration (Tmax), elimination rate constant (kel), and half-life (t1/2). Median pentoxifylline pharmacokinetic parameters after intravenous administration were AUC0-∞ 5420 ng⊙hr/ml, Cmax 16,727 ng/ml, Tmax 5 minutes, k el 0.036 minute-1, and t1/2 19 minutes. Median pharmacokinetic parameters after intranasal and intratracheal administration, respectively, were AUC0-∞ 4224 and 6824 ng⊙hr/ml, C max 11,181 and 16,758 ng/ml, Tmax 5 and 5 minutes, k el 0.028 and 0.032 minute-1, and t1/2 25 and 22 minutes. The metabolite, lisofylline, displayed a similar disposition after the three different routes of administration. Conclusion. The pharmacokinetic profiles after intranasal and intratracheal administration of pentoxifylline appear similar to those after intravenous administration. These data provide support for development of pentoxifylline intranasal and intratracheal dosage formulations that would be suitable for use in premature neonates.