Commonly used drugs in transplant patients:
Antibiotics
Aminoglycosides have outstanding bactericidal acitivity against aerobic gram negative bacilli, Pseudomonas species and mycobacterium species. The clearance of an aminoglycoside is linearly related to the clearance of creatinine since aminoglycosides are nearly entirely eliminated renally and their elimination rate is highly dependent on glomerular filtration rate.
Dosage
The loading doses and maintenance doses for both gentamicin and tobramycin in patients with normal renal function are 2 mg/kg and 1.5 mg/kg every 8 hours, respectively. In patients with renal dysfunction, the interval of subsequent doses to the loading dose may be changed by the equation " creatinine in mg/dl x 8 = dosing interval in hours for an 1 mg/kg of maintenance dose". As in vancomycin, check peak and trough levels at the third dose and maintain peak and trough levels at 4-10 m g/ml and 1-2 m g/ml, respectively. Hemodialysis is known to remove about 50% of the preceding dose in 6 hours. In patients with complete renal failure, a dosage of 1.5-2 mg/kg may be given after each dialysis. Concurrent use of cisplatin, amphotericin-B and cyclosporin may increase the toxic potential of aminoglycosides.
For adults with normal renal function, the dosage of amikacin is 15 mg/kg divided every 8 or 12 hours. In renal dysfunction, after an initial loading dose of 7.5 mg/kg, subsequent doses of 7.5 mg/kg can be given at an interval of " creatinine in mg/dl x 9 = dosing interval in hours ". Maintain serum peak concentrations between 15 and 30 m g/ml, and trough serum concentrations should not exceed 5-10 m g/ml.
The most common toxicity includes reversible renal toxicity, and frequently irreversible and cumulative ototoxicity. Auditory toxicity associated with aminoglycosides is seen clinically as bilateral hearing loss. Transient aminoglycoside levels above the usual limits of 10 m g/ml for gentamicin and tobramycin or 40 m g/ml for amikacin are unlikely to be ototoxic. Risk factors for the development of ototoxicity include the duration of aminoglycoside use, the presence of bacteremia, fever, the concurrent use of large doses of lasix, and the use of vancomycin and cisplatin.
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