Concentrations of tobramycin in human plasma and aqueous humor after intra venous or subconjunctival administration
Sinues, B.; Martinez, P.; Barrera, V.; Palomar, A.
Therapie (London/Paris) 38(4): 345-353
Tobramycin and gentamicin are aminoglucoside antibiotics with similar pharmacological properties. Gentamicin is commonly used in prevention of ocular infections. Tobramycin is less toxic, well accepted and has a larger antibacterial spectrum than gentamicin. Considering the differences between the minimal inhibitory concentrations [MIC] towards ocular infections of the 2 antibiotics, investigations for antiinfection prophylaxis in crystalline cataract extraction were conducted. The concentrations of tobramycin and getamicin in plasma and aqueous humor after i.v. sub-conjunctival administration were studied. Patients (61) were studied immediately before the intervention; plasma and aqueous humor were analyzed by a homogenous enzymoimmunologic method. After sub-conjunctival administration of a dose 4 times lower than an i.v. dose (20 mg instead of 80 mg), efficient concentrations were reached against Pseudomonas aeruginosa and Proteus (MIC: 0.8 mg/ml) in the blood and the eye with a longer duration in vitreous humor. Protection against Serratia (MIC: 6.4 .mu.g/ml) was only obtained in the aqueous humor after sub-conjunctival injection from 30 min until 10 h. I.v. administration does not allow sufficient concentrations to be reached for the inhibition of Serratia growth, while growth of Pseudomonas and Proteus are prevented in both biological fluids.