Tobramycin elimination

Multiple-dose activated charcoal does not increase the elimination of tobramycin and is therefore not recommended for treatment of poisoning (SEDA24.26.74) (51). 

Presentation 1 Conclusion Both vancomycin and tobramycin are adnriinistered with dosing intervals that are longer than the drugs T54. Under these conditions there is little accumulation, and loading doses are not usually administered. Both vancomycin and tobramycin are eliminated from the body primarily by the renal route. BK is a 72-year-old man with a serum Cr level of 2.4 mgAjL As a first estimate, his renal function would appear to be approximately half of the normal value. Using the equation that accounts for age, body size, sex, and serum Cr, his estimated CrCI rate is expected to be approximately 25 ml/min. 

After deposition, antimicrobial therapies are cleared from the lung by various mechanisms, including mucociliary clearance, coughing, and absorption into the systemic circulation. The dmg is then metabolized or eliminated, depending on its properties. The systemic concentrations are severalfold less that what would be achieved with parenteral therapy and would not be expected to cause toxicity. However, more research is warranted to evaluate the impact of patient characteristics on systemic exposure to inhaled antimicrobial therapies. In the clinical trials of the commercially available inhaled tobramycin preparation, the mean concentration achieved one hour after inhalation was approximately 1 p,g/mL. 

Studies in infants have shown that tobramycin clearance during the first postnatal week may increase with an increase in gestational age. In infants up to 1 month after birth, postnatal age also was correlated directly with aminoglycoside clearance. Thus premature infants require a lower daily dose of drugs eliminated by the kidney during the first week of fife the dosage requirement then increases with age. 

The first step is to estimate this patient s pharmacokinetic parameters of tobramycin on the basis of published population data. The volume of distribution in this patient is 23.1 L (0.33 L/kg x 70 kg), and his residual total body clearance (CLres) estimated from the relationship between CL and creatinine clearance [CLres = CLcr X 0.98] is 3 mL/min or 0.176 L/h. The elimination rate constant can be approximated as ... 

There is also evidence from a study in children to show that previous treatment with cisplatin is a risk factor for the delayed elimination of aminoglycosides (gentamicin, amikacin, tobramycin). ... 

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