Abstract
In Japan, tobramycin, one of the aminoglycoside antibiotics, is permitted to be administered only by intramuscular injection when it is used parenterally. But for pediatric patients, intravenous administration of antibiotics, if possible, is more acceptable than intramuscular use
In this study, we compared the efficacy of intravenously and intramuscularly administered tobramycin by the experimental system using diffusion chambers. A 1.2×104 cfu/chamber of Pseudomonas aeruginosa and a 5×105/chamber of rabbit's peritoneal polymorphonuclear leukocytes or only pseudomonas were infused in diffusion chambers with 0.22μm pore sized micropore filters. Then the bacteria and leukocytes were incubated in live peritoneal cavity of the rabbit's and a 2.5 mg/kg of tobramycin was administered by both routes. Intravenous injection was done in 45 minutes using a constant fuel injector. Minimum inhibitory concentration of tobramycin for the test organism was 0.78μg/ml.
Viable bacterial number in the leukocytes containing chambers similarly decreased to 5×102 cfu/chamber by 3 hours after intramuscular and intravenous administration, and slowly increased to reach 1×104cfu/chamber by 12 hours. When leukocytes were not contained in the chambers, viable bacterial numbers decreased to 2×103 cfu/chamber by 3 hours, but increased rapidly to reach more than 3×105 cfu/chamber by 12 hours after both intramuscular and intravenous injections.
The peak concentration in the serum after intramuscular injection was 6.4μug/ml at 15 minutes, and 7.3μg/ml at 45 minutes after intravenous administration. Almost same concentration-time curves of tobramycin in peritoneal fluid were revealed after intramuscular and intravenous administrations.
As a result, tobramycin can be used intravenously as effectively as intramuscular use. Considering the changes of viable bacterial numbers in no-leukocytes containing chambers, short interval between the peak concentrations in the serum might be needed for leukopenic patients. For this purpose, intravenous administration is more suitable than intramuscular injection, which might be acompanied with sever pain, subcutaneous bleeding and contracture of injected muscle.
