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Antimicrobial Agents and Chemotherapy, December 2002, p. 3776-3781, Vol. 46, No. 12
0066-4804/02/$04.00+0     DOI: 10.1128/AAC.46.12.3776-3781.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Pharmacokinetics and Efficacies of Liposomal and Conventional Formulations of Tobramycin after Intratracheal Administration in Rats with Pulmonary Burkholderia cepacia Infection

Jean-Francois Marier,1,2 Jean Lavigne,2 and Murray P. Ducharme1,2*

Faculté de Pharmacie, University of Montreal, Montreal,1 MDS Pharma Services, St-Laurent (Montreal), Quebec, Canada2

Received 28 December 2001/ Returned for modification 19 June 2002/ Accepted 16 August 2002

The objective of the present study was to determine the pharmacokinetics and efficacies of liposomal and conventional formulations of tobramycin against Burkholderia cepacia in a model of chronic lung infection. Male Sprague-Dawley rats were inoculated intratracheally with 106 CFU of a very resistant strain of B. cepacia (strain BC 1368; MIC, 128 µg/ml) to establish lung infection. A 1,200-µg dose of tobramycin was administered intratracheally as a liposomal formulation and as a conventional formulation. Rats were anesthetized and exsanguinated by cardiac puncture at different times over 24 h to assess pulmonary tobramycin concentrations and the number of residual CFU. Pharmacokinetic parameters were calculated by using a two-compartment model with NONMEM. The mean half-life at the ß phase (t1/2ß) and the pulmonary exposure (the area under the concentration-time curve [AUC]) of liposomal tobramycin were 19.7 h (coefficient of variation [CV], 24.2%) and 6,811 µg · h/lungs (CV, 19.7%), respectively. The pharmacokinetics of conventional tobramycin were statistically different, with a t1/2ß and AUC of 12.9 h (CV, 31.4%) and 821 µg · h/lungs (CV, 15.0%), respectively. Pearson chi-square analyses were performed on residual CFU data distributed in the following categories: <103, 103 to 105, and >105. Differences in CFU data between formulations showed a statistical trend (P < 0.10) when data from all time points were used, and statistically significant differences were found after 12 h (P < 0.05), with greater eradication achieved with the liposomal formulation. In conclusion, intratracheal administration of tobramycin in liposomes was associated with marked changes in the pharmacokinetics of the drug in the lung and an apparent trend for a prolonged efficacy against B. cepacia. These results support the hypothesis that inhalation of liposomal tobramycin may improve the management of chronic pulmonary infections caused by resistant bacteria in patients with cystic fibrosis.

* Corresponding author. Mailing address: Pharmacokinetics and Pharmacodynamics, MDS Pharma Services, 2350 Cohen St., St-Laurent (Montreal), Quebec H4R 2N6, Canada. Phone: (514) 333-0042, ext. 4520. Fax: (514) 333-7666. E-mail: Murray.Ducharme{at}mdsps.com.

Antimicrobial Agents and Chemotherapy, December 2002, p. 3776-3781, Vol. 46, No. 12
0066-4804/02/$04.00+0     DOI: 10.1128/AAC.46.12.3776-3781.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.





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