Gentamicin (Page 3 of 4)

Information for Patients

Patients should be counseled that antibacterial drugs including Gentamicin Injection should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Gentamicin Injection is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by Gentamicin Injection or other antibacterial drugs in the future.

ADVERSE REACTIONS:

To report SUSPECTED ADVERSE REACTIONS, contact Fresenius Kabi USA, LLC at 1-800-551-7176 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Nephrotoxicity

Adverse renal effects, as demonstrated by the presence of casts, cells, or protein in the urine or by rising BUN, NPN, serum creatinine or oliguria, have been reported. They occur more frequently in patients treated for longer periods or with larger dosages than recommended.

Neurotoxicity

Serious adverse effects on both vestibular and auditory branches of the eighth nerve have been reported, primarily in patients with renal impairment (especially if dialysis is required), and in patients on high doses and/or prolonged therapy. Symptoms include dizziness, vertigo, tinnitus, roaring in the ears and hearing loss, which, as with other aminoglycosides, may be irreversible. Hearing loss is usually manifested initially by diminution of high-tone acuity. Other factors which may increase the risk of toxicity include excessive dosage, dehydration and previous exposure to other ototoxic drugs.

Peripheral neuropathy or encephalopathy, including numbness, skin tingling, muscle twitching, convulsions and a myasthenia gravis-like syndrome, have been reported.

Note: The risk of toxic reactions is low in neonates, infants and children with normal renal function who do not receive Gentamicin Injection at higher doses or for longer periods of time than recommended.

Other reported adverse reactions possibly related to gentamicin include: respiratory depression, lethargy, confusion, depression, visual disturbances, decreased appetite, weight loss, hypotension and hypertension; rash, itching, urticaria, generalized burning, laryngeal edema, anaphylactoid reactions, fever and headache; nausea, vomiting, increased salivation and stomatitis; purpura, pseudotumor cerebri, acute organic brain syndrome, pulmonary fibrosis, alopecia, joint pain, transient hepatomegaly and splenomegaly.

Laboratory abnormalities possibly related to gentamicin include: increased levels of serum transaminase (SGOT, SGPT), serum LDH and bilirubin, decreased serum calcium, magnesium, sodium and potassium; anemia, leukopenia, granulocytopenia, transient agranulocytosis, eosinophilia, increased and decreased reticulocyte counts and thrombocytopenia. While clinical laboratory test abnormalities may be isolated findings, they may also be associated with clinically related signs and symptoms. For example, tetany and muscle weakness may be associated with hypomagnesemia, hypocalcemia, and hypokalemia.

While local tolerance of Gentamicin Injection is generally excellent, there has been an occasional report of pain at the injection site. Subcutaneous atrophy or fat necrosis suggesting local irritation has been reported rarely.

OVERDOSAGE:

In the event of overdose or toxic reactions, hemodialysis may aid in the removal of gentamicin from the blood, and is especially important if renal function is, or becomes, compromised. The rate of removal of gentamicin is considerably less by peritoneal dialysis than it is by hemodialysis. In the newborn infant, exchange transfusions may also be considered.

DOSAGE AND ADMINISTRATION:

Gentamicin Injection may be given intramuscularly or intravenously. 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.

DOSAGE FOR PATIENTS

WITH NORMAL RENAL FUNCTION

Children: 6 to 7.5 mg/kg/day. (2 to 2.5 mg/kg administered every 8 hours.)

Infants and Neonates: 7.5 mg/kg/day. (2.5 mg/kg administered every 8 hours.)

Premature or Full-term Neonates One Week of Age or Less: 5 mg/kg/day. (2.5 mg/kg administered every 12 hours.)

It is desirable to measure periodically both peak and trough serum concentrations of gentamicin when feasible during therapy to assure adequate but not excessive drug levels. For example, the peak concentration (at 30 to 60 minutes after intramuscular injection) is expected to be in the range of 3 to 5 mcg/mL. When monitoring peak concentrations after intramuscular or intravenous administration, dosage should be adjusted so that prolonged levels above 12 mcg/mL are avoided. When monitoring trough concentrations (just prior to the next dose), dosage should be adjusted so that levels above 2 mcg/mL are avoided. Determination of the adequacy of a serum level for a particular patient must take into consideration the susceptibility of the causative organism, the severity of the infection, and the status of the patient’s host-defense mechanisms.

In patients with extensive burns, altered pharmacokinetics may result in reduced serum concentrations of aminoglycosides. In such patients treated with gentamicin, measurement of serum concentrations is recommended as a basis for dosage adjustment.

The usual duration of treatment is 7 to 10 days. In difficult and complicated infections, a longer course of therapy may be necessary. In such cases monitoring of renal, auditory, and vestibular functions is recommended, since toxicity is more apt to occur with treatment extended for more than 10 days. Dosage should be reduced if clinically indicated.

For Intravenous Administration

The intravenous administration of gentamicin may be particularly useful for treating patients with bacterial septicemia or those in shock. It may also be the preferred route of administration for some patients with congestive heart failure, hematologic disorders, severe burns, or those with reduced muscle mass.

For intermittent intravenous administration, a single dose of Gentamicin Injection may be diluted in 0.9% Sodium Chloride Injection or in 5% Dextrose Injection. The solution may be infused over a period of one-half to two hours.

The recommended dosage for intravenous and intramuscular administration is identical.

Gentamicin Injection should not be physically premixed with other drugs, but should be administered separately in accordance with the recommended route of administration and dosage schedule.

DOSAGE FOR PATIENTS

WITH IMPAIRED RENAL FUNCTION

Dosage must be adjusted in patients with impaired renal function to assure therapeutically adequate but not excessive, blood levels. Whenever possible, serum concentrations of gentamicin should be monitored. One method of dosage adjustment is to increase the interval between administration of the usual doses. Since the serum creatinine concentration has a high correlation with the serum half-life of gentamicin, this laboratory test may provide guidance for adjustment of the interval between doses. In adults, the interval between doses (in hours) may be approximated by multiplying the serum creatinine level (mg/100 mL) by 8. For example, a patient weighing 60 kg with a serum creatinine level of 2 mg/100 mL could be given 60 mg (1 mg/kg) every 16 hours (2 x 8). These guidelines may be considered when treating infants and children with serious renal impairment.

In patients with serious systemic infections and renal impairment, it may be desirable to administer the antibiotic more frequently but in reduced dosage. In such patients, serum concentrations of gentamicin should be measured so that adequate but not excessive levels result.

A peak and trough concentration measured intermittently during therapy will provide optimal guidance for adjusting dosage. After the usual initial dose, a rough guide for determining reduced dosage at eight-hour intervals is to divide the normally recommended dose by the serum creatinine level (Table 3). For example, after an initial dose of 20 mg (2 mg/kg), a child weighing 10 kg with a serum creatinine level of 2 mg/100 mL could be given 10 mg every eight hours (20 ÷ 2). It should be noted that the status of renal function may be changing over the course of the infectious process. It is important to recognize that deteriorating renal function may require a greater reduction in dosage than that specified in the above guidelines for patients with stable renal impairment.

TABLE 3 DOSAGE ADJUSTMENT GUIDE FOR PATIENTS WITH RENAL IMPAIRMENT (Dosage at Eight-Hour Intervals After the Usual Initial Dose)
SerumCreatinine(mg %) ApproximateCreatinineClearance Rate(mL/min/1.73m2) Percent ofUsual DosesShown Above
≤1 >100 100
1.1 to 1.3 70 to 100 80
1.4 to 1.6 55 to 70 65
1.7 to 1.9 45 to 55 55
2 to 2.2 40 to 45 50
2.3 to 2.5 35 to 40 40
2.6 to 3 30 to 35 35
3.1 to 3.5 25 to 30 30
3.6 to 4 20 to 25 25
4.1 to 5.1 15 to 20 20
5.2 to 6.6 10 to 15 15
6.7 to 8 <10 10

In patients with renal failure undergoing hemodialysis, the amount of gentamicin removed from the blood may vary depending upon several factors including the dialysis method used. An eight-hour hemodialysis may reduce serum concentrations of gentamicin by approximately 50%. In children, the recommended dose at the end of each dialysis period is 2 to 2.5 mg/kg depending upon the severity of the infection.

The above dosage schedules are not intended as rigid recommendations but are provided as guides to dosage when the measurement of gentamicin serum levels is not feasible.

A variety of methods are available to measure gentamicin concentrations in body fluids; these include microbiologic, enzymatic and radioimmunoassay techniques.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

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