Tobramycin (Page 2 of 4)

INDICATIONS & USAGE

Tobramycin for Injection, USP is indicated for the treatment of serious bacterial infections caused by susceptible strains of the designated microorganisms in the diseases listed below:

Septicemia in the pediatric patient and adult caused by P. aeruginosa, E. coli, and Klebsiella spp

Lower respiratory tract infections caused by P. aeruginosa, Klebsiella spp, Enterobacter spp, Serratia spp, E. coli , and S. aureus (penicillinase- and non-penicillinase-producing strains)

Serious central-nervous-system infections (meningitis) caused by susceptible organisms

Intra-abdominal infections, including peritonitis, caused by E. coli, Klebsiella spp, and Enterobacter spp

Skin, bone, and skin structure infections caused by P. aeruginosa , Proteus spp, E. coli , Klebsiella spp, Enterobacter s pp, and S. aureus

Complicated and recurrent urinary tract infections caused by P. aeruginosa , Proteus spp (indole-positive and indole-negative), E. coli , Klebsiella spp, Enterobacter spp, Serratia spp, S. aureus , Providencia spp, and Citrobacter spp

Aminoglycosides, including tobramycin for injection USP, are not indicated in uncomplicated initial episodes of urinary tract infections unless the causative organisms are not susceptible to antibiotics having less potential toxicity. Tobramycin for Injection, USP may be considered in serious staphylococcal infections when penicillin or other potentially less toxic drugs are contraindicated and when bacterial susceptibility testing and clinical judgment indicate its use.

Bacterial cultures should be obtained prior to and during treatment to isolate and identify etiologic organisms and to test their susceptibility to tobramycin. If susceptibility tests show that the causative organisms are resistant to tobramycin, other appropriate therapy should be instituted. In patients in whom a serious life-threatening gram-negative infection is suspected, including those in whom concurrent therapy with a penicillin or cephalosporin and an aminoglycoside may be indicated, treatment with Tobramycin for Injection, USP may be initiated before the results of susceptibility studies are obtained. The decision to continue therapy with Tobramycin for Injection, USP should be based on the results of susceptibility studies, the severity of the infection, and the important additional concepts discussed in the Warnings box above.

To reduce the development of drug-resistant bacteria and maintain the effectiveness of tobramycin and other antibacterial drugs, Tobramycin for Injection, USP should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

CONTRAINDICATIONS

A hypersensitivity to any aminoglycoside is a contraindication to the use of tobramycin. A history of hypersensitivity or serious toxic reactions to aminoglycosides may also contraindicate the use of any other aminoglycoside because of the known cross-sensitivity of patients to drugs in this class.

WARNINGS

See Warnings box above.

Serious allergic reactions including anaphylaxis and dermatologic reactions including exfoliative dermatitis, toxic epidermal necrolysis, erythema multiforme, and

Stevens-Johnson Syndrome have been reported rarely in patients on tobramycin therapy. Although rare, fatalities have been reported. (See CONTRAINDICATIONS).

If an allergic reaction occurs, the drug should be discontinued and appropriate therapy instituted.

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including Tobramycin for Injection, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management,protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated.

PRECAUTIONS

General

Prescribing tobramycin in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

Serum and urine specimens for examination should be collected during therapy, as recommended in the Warnings box. Serum calcium, magnesium, and sodium should be monitored.

Peak and trough serum levels should be measured periodically during therapy. Prolonged concentrations above 12 mcg/mL should be avoided. Rising trough levels (above 2 mcg/mL) may indicate tissue accumulation. Such accumulation, advanced age, and cumulative dosage may contribute to ototoxicity and nephrotoxicity. It is particularly important to monitor serum levels closely in patients with known renal impairment.

A useful guideline would be to perform serum level assays after 2 or 3 doses, so that the dosage could be adjusted if necessary, and at 3- to 4-day intervals during therapy. In the event of changing renal function, more frequent serum levels should be obtained and the dosage or the dosage interval adjusted according to the guidelines provided in the Dosage and Administration section.

In order to measure the peak level, a serum sample should be drawn about 30 minutes following intravenous infusion or 1 hour after an intramuscular injection. Trough levels are measured by obtaining serum samples at 8 hours or just prior to the next dose of tobramycin. These suggested time intervals are intended only as guidelines and may vary according to institutional practices. It is important, however, that there be consistency within the individual patient program unless computerized pharmacokinetic dosing programs are available in the institution. These serum-level assays may be especially useful for monitoring the treatment of severely ill patients with changing renal function or of those infected with less susceptible organisms or those receiving maximum dosage.

Neuromuscular blockade and respiratory paralysis have been reported in cats receiving very high doses of tobramycin (40 mg/kg). The possibility of prolonged or secondary apnea should be considered if tobramycin is administered to anesthetized patients who are also receiving neuromuscular blocking agents, such as succinyl choline, tubocurarine, or decamethonium, or to patients receiving massive transfusions of citrated blood. If neuromuscular blockade occurs, it may be reversed by the administration of calcium salts.

Cross-allergenicity among aminoglycosides has been demonstrated.

In patients with extensive burns or cystic fibrosis, altered pharmacokinetics may result in reduced serum concentrations of aminoglycosides. In such patients treated with tobramycin, measurement of serum concentration is especially important as a basis for determination of appropriate dosage.

Elderly patients may have reduced renal function that may not be evident in the results of routine screening tests, such as BUN or serum creatinine. A creatinine clearance determination may be more useful. Monitoring of renal function during treatment with aminoglycosides is particularly important in such patients.

An increased incidence of nephrotoxicity has been reported following concomitant administration of aminoglycoside antibiotics and cephalosporins.

Aminoglycosides should be used with caution in patients with muscular disorders, such as myasthenia gravis or parkinsonism, since these drugs may aggravate muscle weakness because of their potential curare-like effect on neuromuscular function.

Aminoglycosides may be absorbed in significant quantities from body surfaces after local irrigation or application and may cause neurotoxicity and nephrotoxicity.

Aminoglycosides have not been approved for intraocular and/or subconjunctival use. Physicians are advised that macular necrosis has been reported following administration of aminoglycosides, including tobramycin, by these routes.

See Warnings box regarding concurrent use of potent diuretics and concurrent and sequential use of other neurotoxic or nephrotoxic drugs.

The inactivation of tobramycin and other aminoglycosides by β-lactam-type antibiotics (penicillins or cephalosporins) has been demonstrated in vitro and in patients with severe renal impairment. Such inactivation has not been found in patients with normal renal function who have been given the drugs by separate routes of administration.

Therapy with tobramycin may result in overgrowth of nonsusceptible organisms. If overgrowth of nonsusceptible organisms occurs, appropriate therapy should be initiated.

Information for Patients

Patients should be counseled that antibacterial drugs including tobramycin should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When Tobramycin for 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 not be treatable by tobramycin or any other antibacterial drugs in the future.

Pregnancy Category D Aminoglycosides can cause fetal harm when administered to a pregnant woman. Aminoglycoside antibiotics cross the placenta, and there have been several reports of total irreversible bilateral congenital deafness in children whose mothers received streptomycin during pregnancy. Serious side effects to mother, fetus, or newborn have not been reported in the treatment of pregnant women with other aminoglycosides. If tobramycin is used during pregnancy or if the patient becomes pregnant while taking tobramycin, she should be apprised of the potential hazard to the fetus.

Diarrhea is a common problem caused by antibiotics, which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.

Pediatric Use

See Indications and Usage and Dosage and Administration.

Geriatric Use
Elderly patients may be at a higher risk of developing nephrotoxicity and ototoxicity while receiving tobramycin (see WARNINGS, PRECAUTIONS and OVERDOSAGE). Other factors that may contribute to nephrotoxicity and ototoxicity are rising trough levels, excessive peak concentrations, dehydration, concomitant use of other neurotoxic or nephrotoxic drugs, and cumulative dose. Peak and trough serum levels should be measured periodically during therapy to assure adequate levels and to avoid potentially toxic levels (see WARNINGS and PRECAUTIONS).
Tobramycin is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function (see DOSAGE AND ADMINISTRATION). Elderly patients may have reduced renal function that may not be evident in the results of routine screening tests, such as BUN or serum creatinine. A creatinine clearance determination may be more useful. Monitoring of renal function during treatment with aminoglycosides is particularly important in the elderly (see PRECAUTIONS). This product does not contain sodium.

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