Amikacin

Mechanism of Action Amikacin, an aminoglycoside, binds to the prokaryotic ribosome, inhibiting protein synthesis in susceptible bacteria. It is bactericidal in vitro against Gram-positive and Gram-negative bacteria.

INDICATIONS AND USAGE Amikacin Sulfate Injection is indicated in the short-term treatment of serious infections due to susceptible strains of Gram-negative bacteria, including Pseudomonas species, Escherichia coli , species of indole-positive and indole-negative Proteus , Providencia species, Klebsiella-Enterobacter-Serratia species, and Acinetobacter ( Mima-Herellea ) species. Clinical studies have shown Amikacin Sulfate Injection to be effective in bacterial septicemia (including neonatal sepsis); in serious infections of the respiratory tract, bones and joints, central nervous system (including meningitis) and skin and soft tissue; intra-abdominal infections (including peritonitis); and in burns and post-operative infections (including post-vascular surgery). Clinical studies have shown amikacin also to be effective in serious complicated and recurrent urinary tract infections due to these organisms. Aminoglycosides, including Amikacin Sulfate Injection are not indicated in uncomplicated initial episodes of urinary tract infections unless the causative organisms are not susceptible to antibiotics having less potential toxicity. Bacteriologic studies should be performed to identify causative organisms and their susceptibilities to amikacin. Amikacin may be considered as initial therapy in suspected Gram-negative infections and therapy may be instituted before obtaining the results of susceptibility testing. Clinical trials demonstrated that amikacin was effective in infections caused by gentamicin- and/or tobramycin-resistant strains of Gram-negative organisms, particularly Proteus rettgeri , Providencia stuartii , Serratia marcescens , and Pseudomonas aeruginosa . The decision to continue therapy with the drug should be based on results of the susceptibility tests, the severity of the infection, the response of the patient and the important additional considerations contained in the WARNINGS box above. Amikacin has also been shown to be effective in staphylococca

DOSAGE AND ADMINISTRATION The patient’s pretreatment body weight should be obtained for calculation of correct dosage. Amikacin Sulfate Injection may be given intramuscularly or intravenously. The status of renal function should be estimated by measurement of the serum creatinine concentration or calculation of the endogenous creatinine clearance rate. The blood urea nitrogen (BUN) is much less reliable for this purpose. Reassessment of renal function should be made periodically during therapy. Whenever possible, amikacin concentrations in serum should be measured to assure adequate but not excessive levels. It is desirable to measure both peak and trough serum concentrations intermittently during therapy. Peak concentrations (30 to 90 minutes after injection) above 35 micrograms per mL and trough concentrations (just prior to the next dose) above 10 micrograms per mL should be avoided. Dosage should be adjusted as indicated. Intramuscular Administration for Patients with Normal Renal Function The recommended dosage for adults, children and older infants (see WARNINGS box) with normal renal function is 15 mg/kg/day divided into 2 or 3 equal doses administered at equally-divided intervals, i.e., 7.5 mg/kg q12h or 5 mg/kg q8h. Treatment of patients in the heavier weight classes should not exceed 1.5 gram/day. When amikacin is indicated in newborns (see WARNINGS box), it is recommended that a loading dose of 10 mg/kg be administered initially to be followed with 7.5 mg/kg every 12 hours. The usual duration of treatment is 7 to 10 days. It is desirable to limit the duration of treatment to short term whenever feasible. The total daily dose by all routes of administration should not exceed 15 mg/kg/day. In difficult and complicated infections where treatment beyond 10 days is considered, the use of amikacin should be reevaluated. If continued, amikacin serum levels, and renal, auditory, and vestibular functions should be monitored. At the recommended dosage level, uncomplicated infections due to amikacin-sensitive organisms should respond in 24 to 48 hours. If definite clinical response does not occur within 3 to 5 days, therapy should be stopped and the antibiotic susceptibility pattern of the invading organism should be rechecked. Failure of the infection to respond may be due to resistance of the organism or to the presence of septic foci requiring surgical drainage. When amikacin is indicated in uncomplicated urinary tract infections, a dose of 250 mg twice daily may be used. DOSAGE GUIDELINES ADULTS AND CHILDREN WITH NORMAL RENAL FUNCTION Patient Weight Dosage lbs kg 7.5 mg/kg q12h OR 5 mg/kg q8h 99 45 337.5 mg 225 mg 110 50 375 mg 250 mg 121 55 412.5 mg 275 mg 132 60 450 mg 300 mg 143 65 487.5 mg 325 mg 154 70 525 mg 350 mg 165 75 562.5 mg 375 mg 176 80 600 mg 400 mg 187 85 637.5 mg 425 mg 198 90 675 mg 450 mg 209 95 712.5 mg 475 mg 220 100 750 mg 500 mg Intramuscular Administration for Patients with Impaired Renal Function Whenever possible, serum amikacin concentrations should be monitored by appropriate assay procedures. Doses may be adjusted in patients with impaired renal function either by administering normal doses at prolonged intervals or by administering reduced doses at a fixed interval. Both methods are based on the patient’s creatinine clearance or serum creatinine values since these have been found to correlate with aminoglycoside half-lives in patients with diminished renal function. These dosage schedules must be used in conjunction with careful clinical and laboratory observations of the patient and should be modified as necessary. Neither method should be used when dialysis is being performed. Normal Dosage at Prolonged Intervals If the creatinine clearance rate is not available and the patient’s condition is stable, a dosage interval in hours for the normal dose can be calculated by multiplying the patient’s serum creatinine by 9, e.g., if the serum creatinine concentration is 2 mg/100 mL, the recommended single dose (7.5 mg/kg) should be administered every 18 hours. Reduced Dosage at Fixed Time Intervals When renal function is impaired and it is desirable to administer amikacin at a fixed time interval, dosage must be reduced. In these patients, serum amikacin concentrations should be measured to assure accurate administration of amikacin and to avoid concentrations above 35 mcg/mL. If serum assay determinations are not available and the patient’s condition is stable, serum creatinine and creatinine clearance values are the most readily available indicators of the degree of renal impairment to use as a guide for dosage. First, initiate therapy by administering a normal dose, 7.5 mg/kg, as a loading dose. This loading dose is the same as the normally recommended dose which would be calculated for a patient with a normal renal function as described above. To determine the size of maintenance doses administered every 12 hours, the loading dose should be reduced in proportion to the reducti

ADVERSE REACTIONS All aminoglycosides have the potential to induce auditory, vestibular, and renal toxicity and neuromuscular blockade (see WARNINGS box). They occur more frequently in patients with present or past history of renal impairment, of treatment with other ototoxic or nephrotoxic drugs, and in patients treated for longer periods and/or with higher doses than recommended. Neurotoxicity-Ototoxicity Toxic effects on the eighth cranial nerve can result in hearing loss, loss of balance, or both. Amikacin primarily affects auditory function. Cochlear damage includes high frequency deafness and usually occurs before clinical hearing loss can be detected. Neurotoxicity-Neuromuscular Blockade Acute muscular paralysis and apnea can occur following treatment with aminoglycoside drugs. Nephrotoxicity Elevation of serum creatinine, albuminuria, presence of red and white cells, casts, azotemia, and oliguria have been reported. Renal function changes are usually reversible when the drug is discontinued. As would be expected with any aminoglycoside, reports of toxic nephropathy and acute renal failure have been received during postmarketing surveillance. Other In addition to those described above, other adverse reactions which have been reported on rare occasions are skin rash, drug fever, headache, paresthesia, tremor, nausea and vomiting, eosinophilia, arthralgia, anemia, hypotension and hypomagnesemia. Macular infarction sometimes leading to permanent loss of vision has been reported following intravitreous administration (injection into the eye) of amikacin.