Amikacin Sulfate

AMIKACIN SULFATE- amikacin sulfate injection
West-Ward Pharmaceutical Corp.

Rx only

To reduce the development of drug-resistant bacteria and maintain the effectiveness of the amikacin and other antibacterial drugs, amikacin should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

WARNINGS

Patients treated with parenteral aminoglycosides should be under close clinical observation because of the potential ototoxicity and nephrotoxicity associated with their use. Safety for treatment periods which are longer than 14 days has not been established.

Neurotoxicity, manifested as vestibular and permanent bilateral auditory ototoxicity, can occur in patients with preexisting renal damage and in patients with normal renal function treated at higher doses and/or for periods longer than those recommended. The risk of aminoglycoside-induced ototoxicity is greater in patients with renal damage. High frequency deafness usually occurs first and can be detected only by audiometric testing. Vertigo may occur and may be evidence of vestibular injury. Other manifestations of neurotoxicity may include numbness, skin tingling, muscle twitching and convulsions. The risk of hearing loss due to aminoglycosides increases with the degree of exposure to either high peak or high trough serum concentrations. Patients developing cochlear damage may not have symptoms during therapy to warn them of developing eighth-nerve toxicity, and total or partial irreversible bilateral deafness may occur after the drug has been discontinued. Aminoglycoside-induced ototoxicity is usually irreversible.

Aminoglycosides are potentially nephrotoxic. The risk of nephrotoxicity is greater in patients with impaired renal function and in those who receive high doses or prolonged therapy.

Neuromuscular blockade and respiratory paralysis have been reported following parenteral injection, topical instillation (as in orthopedic and abdominal irrigation or in local treatment of empyema), and following oral use of aminoglycosides. The possibility of these phenomena should be considered if aminoglycosides are administered by any route, especially in patients receiving anesthetics, neuromuscular blocking agents such as tubocurarine, succinylcholine, decamethonium, or in patients receiving massive transfusions of citrate-anticoagulated blood. If blockage occurs, calcium salts may reverse these phenomena, but mechanical respiratory assistance may be necessary.

Renal and eighth-nerve function should be closely monitored especially in patients with known or suspected renal impairment at the onset of therapy and also in those whose renal function is initially normal but who develop signs of renal dysfunction during therapy. Serum concentrations of amikacin should be monitored when feasible to assure adequate levels and to avoid potentially toxic levels and prolonged peak concentrations above 35 micrograms per mL. Urine should be examined for decreased specific gravity, increased excretion of proteins, and the presence of cells or casts. Blood urea nitrogen, serum creatinine, or creatinine clearance should be measured periodically. Serial audiograms should be obtained where feasible in patients old enough to be tested, particularly high risk patients. Evidence of ototoxicity (dizziness, vertigo, tinnitus, roaring in the ears, and hearing loss) or nephrotoxicity requires discontinuation of the drug or dosage adjustment.

Concurrent and/or sequential systemic, oral or topical use of other neurotoxic or nephrotoxic products, particularly bacitracin, cisplatin, amphotericin B, cephaloridine, paromomycin, viomycin, polymyxin B, colistin, vancomycin, or other aminoglycosides should be avoided. Other factors that may increase risk of toxicity are advanced age and dehydration.

The concurrent use of amikacin with potent diuretics (ethacrynic acid, or furosemide) should be avoided since diuretics by themselves may cause ototoxicity. In addition, when administered intravenously, diuretics may enhance aminoglycoside toxicity by altering antibiotic concentrations in serum and tissue.

DESCRIPTION

Amikacin sulfate is semi-synthetic aminoglycoside antibiotic derived from kanamycin. It is C22 H43 N5 O13 •2H2 SO4O -3-amino-3-deoxy-α-D-glucopyranosyl-(1→4)-O -[6-amino-6-deoxy-α-D-glucopyranosyl-(1→6)]-N3 -(4-amino-L-2-hydroxybutyryl)-2-deoxy-L-streptamine sulfate (1:2)

chemical structure
(click image for full-size original)

M.W. 585.61

The dosage form is supplied as a sterile, colorless to light straw colored solution for intramuscular or intravenous use. Each mL contains 250 mg amikacin (as the sulfate), 0.66% sodium metabisulfite, 2.5% sodium citrate dihydrate with pH adjusted to 3.5 to 5.5 with sulfuric acid.

CLINICAL PHARMACOLOGY

Intramuscular Administration

Amikacin is rapidly absorbed after intramuscular administration. In normal adult volunteers, average peak serum concentrations of about 12, 16, and 21 mcg/mL are obtained 1 hour after intramuscular administration of 250 mg (3.7 mg/kg), 375 mg (5 mg/kg), 500 mg (7.5 mg/kg), single doses, respectively. At 10 hours, serum levels are about 0.3 mcg/mL, 1.2 mcg/mL, and 2.1 mcg/mL, respectively.

Tolerance studies in normal volunteers reveal that amikacin is well tolerated locally following repeated intramuscular dosing, and when given at maximally recommended doses, no ototoxicity or nephrotoxicity has been reported. There is no evidence of drug accumulation with repeated dosing for 10 days when administered according to recommended doses.

With normal renal function, about 91.9% of an intramuscular dose is excreted unchanged in the urine in the first 8 hours, and 98.2% within 24 hours. Mean urine concentrations for 6 hours are 563 mcg/mL following a 250 mg dose, 697 mcg/mL following a 375 mg dose, and 832 mcg/mL following a 500 mg dose.

Preliminary intramuscular studies in newborns of different weights (less than 1.5 kg, 1.5 to 2 kg, over 2 kg) at a dose of 7.5 mg/kg revealed that, like other aminoglycosides, serum half-life values were correlated inversely with post-natal age and renal clearances of amikacin. The volume of distribution indicates that amikacin, like other aminoglycosides, remains primarily in the extracellular fluid space of neonates. Repeated dosing every 12 hours in all the above groups did not demonstrate accumulation after 5 days.

Intravenous Administration

Single doses of 500 mg (7.5 mg/kg) administered to normal adults as an infusion over a period of 30 minutes produced a mean peak serum concentration of 38 mcg/mL at the end of the infusion, and levels of 24 mcg/mL, 18 mcg/mL, and 0.75 mcg/mL at 30 minutes, 1 hour, and 10 hours post-infusion, respectively. Eighty-four percent of the administered dose was excreted in the urine in 9 hours and about 94% within 24 hours.

Repeat infusions of 7.5 mg/kg every 12 hours in normal adults were well tolerated and caused no drug accumulation.

General

Pharmacokinetic studies in normal adult subjects reveal the mean serum half-life to be slightly over 2 hours with a mean total apparent volume of distribution of 24 liters (28% of the body weight). By the ultrafiltration technique, reports of serum protein binding range from 0 to 11%. The mean serum clearance rate is about 100 mL/min and the renal clearance rate is 94 mL/min in subjects with normal renal function.

Amikacin is excreted primarily by glomerular filtration. Patients with impaired renal function or diminished glomerular filtration pressure excrete the drug much more slowly (effectively prolonging the serum half-life). Therefore, renal function should be monitored carefully and dosage adjusted accordingly (see suggested dosage schedule under DOSAGE AND ADMINISTRATION).

Following administration at the recommended dose, therapeutic levels are found in bone, heart, gallbladder, and lung tissue in addition to significant concentrations in urine, bile, sputum, bronchial secretions, interstitial, pleural, and synovial fluids.

Spinal fluid levels in normal infants are approximately 10 to 20% of the serum concentrations and may reach 50% when the meninges are inflamed. Amikacin has been demonstrated to cross the placental barrier and yield significant concentrations in amniotic fluid. The peak fetal serum concentration is about 16% of the peak maternal serum concentration and maternal and fetal serum half-life values are about 2 and 3.7 hours, respectively.

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