Gentamicin warnings and precautions

# Warnings and Precautions

### Warnings
Contains sodium metabisulfite, a sulfite that may cause allergic-type reactions including anaphylactic symptoms and life-threatening or less severe asthmatic episodes in certain susceptible people.  The overall prevalence of sulfite sensitivity in the general population is unknown and probably low.  Sulfite sensitivity is seen more frequently in asthmatic than in non-asthmatic people.
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.  Animal reproduction studies conducted on rats and rabbits did not reveal evidence of impaired fertility or harm to the fetus due to gentamicin sulfate.
It is not known whether gentamicin sulfate can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity.  If gentamicin is used during pregnancy or if the patient becomes pregnant while taking gentamicin, she should be apprised of the potential hazard to the fetus.

### Precautions
Prescribing Gentamicin Injection, USP 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.
Neurotoxic and nephrotoxic antibiotics may be almost completely absorbed from body surfaces (except urinary bladder) after local irrigation and after topical application during surgical procedures.  The potential toxic effects of antibiotics administered in this fashion (neuromuscular blockage, respiratory paralysis, ototoxicity and nephrotoxicity) should be considered (see boxed WARNINGS).
Increased nephrotoxicity has been reported following concomitant administration of aminoglycoside antibiotics and cephalosporins.
Neuromuscular blockade and respiratory paralysis have been reported in the cat receiving high doses (40 mg/kg) of gentamicin.  The possibility of these phenomena occurring in man should be considered if aminoglycosides are administered by any route to patients receiving anesthetics, or to patients receiving neuromuscular blocking agents, such as succinylcholine, tubocurarine or decamethonium, or in patients receiving massive transfusions of citrate-anticoagulated blood.  If neuromuscular blockade occurs, calcium salts may reverse it.
Aminoglycosides should be used with caution in patients with neuromuscular disorders, such as myasthenia gravis or parkinsonism, since these drugs may aggravate muscle weakness because of their potential curare-like effects on the neuromuscular junction.  During or following gentamicin therapy, paresthesias, tetany, positive Chvostek and Trousseau signs and mental confusion have been described in patients with hypomagnesemia, hypocalcemia and hypokalemia.  When this has occurred in infants, tetany and muscle weakness has been described.  Both adults and infants required corrective electrolyte therapy.
Elderly patients may have reduced renal function which 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 gentamicin, as with other aminoglycosides, is particularly important in such patients.  A Fanconi-like syndrome, with aminoaciduria and metabolic acidosis has been reported in some adults and infants being given gentamicin injections.
Cross-allergenicity among aminoglycosides has been demonstrated.
Patients should be well hydrated during treatment.
Although the in vitro mixing of gentamicin and carbenicillin results in a rapid and significant inactivation of gentamicin, this interaction has not been demonstrated in patients with normal renal function who received both drugs by different routes of administration.  A reduction in gentamicin serum half-life has been reported in patients with severe renal impairment receiving carbenicillin concomitantly with gentamicin.
Treatment with gentamicin may result in overgrowth of nonsusceptible organisms.  If this occurs, appropriate therapy is indicated.
See boxed WARNINGS regarding concurrent use of potent diuretics and regarding concurrent and/or sequential use of other neurotoxic and/or for other essential information.
Patients should be counseled that antibacterial drugs including Gentamicin Injection, USP should only be used to treat bacterial infections.  They do not treat viral infections (e.g., the common cold).  When Gentamicin Injection, USP 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, USP or other antibacterial drugs in the future.
See WARNINGS section.