BOXED WARNINGS Patients treated with aminoglycosides should be under close clinical observation because of the potential toxicity associated with their use. As with other aminoglycosides, gentamicin injection is potentially nephrotoxic. The risk of nephrotoxicity is greater in patients with impaired renal function and in those who receive high dosage of prolonged therapy. Neurotoxicity manifested by ototoxicity, both vestibular and auditory, can occur in patients treated with gentamicin, primarily in those with pre-existing renal damage and in patients with normal renal function treated with higher doses and/or for longer periods than recommended. Aminoglycoside-induced ototoxicity is usually irreversible. Other manifestations of neurotoxicity may include numbness, skin tingling, muscle twitching and convulsions. Renal and eighth cranial nerve function should be closely monitored, especially in patients with known or suspected reduced renal function at onset of therapy and also in those whose renal function is initially normal but who develop signs of renal dysfunction during therapy. Urine should be examined for decreased specific gravity, increased excretion of protein and the presence of cells or casts. Blood urea nitrogen (BUN), serum creatinine or creatinine clearance should be determined periodically. When feasible, it is recommended that serial audiograms be obtained in patients old enough to be tested, particularly high-risk patients. Evidence of ototoxicity (dizziness, vertigo, tinnitus, roaring in the ears or hearing loss) or nephrotoxicity requires dosage adjustment or discontinuance of the drug. As with the other aminoglycosides, on rare occasions changes in renal and eighth cranial nerve function may not become manifest until soon after completion of therapy. Serum concentrations of aminoglycosides should be monitored when feasible to assure adequate levels and to avoid potentially toxic levels. When monitoring gentamicin peak concentrations, dosage should be adjusted so that prolonged levels above 12 mcg/mL are avoided. When monitoring gentamicin trough concentrations, dosage should be adjusted so that levels above 2 mcg/mL are avoided. Excessive peak and/or trough serum concentrations of aminoglycosides may increase the risk of renal and eighth cranial nerve toxicity. In the event of overdosage or toxic reactions, hemodialysis may aid in the removal of gentamicin from the blood, especially if renal function is, or becomes, compromised. The rate of removal of gentamicin is considerably lower by peritoneal dialysis than it is by hemodialysis. In the newborn infant, exchange transfusions may also be considered. Concurrent and/or sequential systemic or topical use of other potentially neurotoxic and/or nephrotoxic drugs, such as cisplatin, cephaloridine, kanamycin, amikacin, neomycin, polymyxin B, colistin, paromomycin, streptomycin, tobramycin, vancomycin and viomycin, should be avoided. Other factors which may increase patient risk o...
Adult Dosing
General dosing
: Gentamicin injection may be given IM or IV. The patient’s pretreatment body weight should be obtained for calculation of correct dosage. The dosage of aminoglycosides in obese patients should be based on an estimate of the lean body mass. It is desirable to limit the duration of treatment with aminoglycosides to short term. PATIENTS WITH NORMAL RENAL FUNCTION Adults The recommended dosage of gentamicin injection for patients with serious infections and normal renal function is 3 mg/kg/day, administered in three equal doses every eight hours (Table 3) . For patients with life-threatening infections, dosages up to 5 mg/kg/day may be administered in three or four equal doses. This dosage should be reduced to 3 mg/kg/day as soon as clinically indicated (Table 3) . It is desirable to measure both peak and trough serum concentrations of gentamicin to determine the adequacy and safety of the dosage. When such measurements are feasible, they should be carried out periodically during therapy to assure adequate but not excessive drug levels. For example, the peak concentration (at 30 to 60 minutes after IM injection) is expected to be in the range of 4 to 6 mcg/mL.
General dosing
ADULTS WITH NORMAL RENAL FUNCTION (Dosage at Eight-Hour Intervals) 40 mg per mL Patient’s Weight* Usual Dose for Serious Infections 1 mg/kg q8h (3 mg/kg/day) Dose for Life-Threatening Infections (Reduce As Soon As Clinically Indicated) 1.7 mg/kg q8h** (5 mg/kg/day) kg (lb) mg/dose mL/dose mg/dose mL/dose q8h q8h 40 40 1 66 1.6 45 45 1.1 75 1.9 50 50 1.25 83 2.1 55 55 1.4 91 2.25 60 60 1.5 100 2.5 65 65 1.6 108 2.7 70 70 1.75 116 2.9 75 75 1.9 125 3.1 80 80 2 133 3.3 85 85 2.1 141 3.5 90 90 2.25 150 3.75 95 95 2.4 158 4 100 100 2.5 166 4.2 *The dosage of aminoglycosides in obese patients should be based on an estimate of the lean body mass. **for q6h schedules, dosage should be recalculated. Children 6 to 7.5 mg/kg/day (2 to 2.5 mg/kg administered every eight hours). Infants and Neonates 7.5 mg/kg/day (2.5 mg/kg administered every eight hours). Premature or Full-Term Neonates One Week of Age or Less 5 mg/kg/day (2.5 mg/kg administered every 12 hours). For further information concerning the use of gentamicin in infants and children, see gentamicin injection (pediatric) product information. The usual duration of treatment for all patients is 7 to 10 days.
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