TOBRAMYCIN SULFATE
(toe-bra-mye'sin)
Tobrex, TOBI, Tomycine
Classifications: antiinfective; aminoglycoside antibiotic
Prototype: Gentamicin sulfate
Pregnancy Category: D

Availability

10 mg/mL, 40 mg/mL injection; 300 mg/5 mL inhalation solution; 0.3% ophthalmic solution; 3 mg/g ophthalmic ointment

Actions

Broad-spectrum, aminoglycoside antibiotic derived from Streptomyces tenebrarius. Closely related to gentamicin in spectrum of antibacterial activity and pharmacologic properties. Reportedly causes less nephrotoxicity than gentamicin, but incidence of ototoxicity is similar. Cross-allergenicity and some cross-resistance among aminoglycosides have been demonstrated.

Therapeutic Effects

Exhibits greater antibiotic activity against Pseudomonas aeruginosa than other aminoglycosides.

Uses

Treatment of severe infections caused by susceptible organisms.

Contraindications

History of hypersensitivity to tobramycin and other aminoglycoside antibiotics. Safety during pregnancy (category D) or lactation is not established.

Cautious Use

Impaired kidney function; premature and neonatal infants; concurrent use with other neurotoxic or nephrotoxic agents or potent diuretics

Route & Dosage

Moderate to Severe Infections
Adult: IV 3 mg/kg/d divided q8h up to 5 mg/kg/d infused over 20–60 min IM 3 mg/kg/d divided q8h up to 5 mg/kg/d Topical 1–2 drops in affected eye q1–4h
Child: IM/IV <5 y, 2.5 mg/kg q8h IV 5 y, 3 mg/kg/d divided q8h up to 5 mg/kg/d infused over 20–60 min IM 5 y, 3 mg/kg/d divided q8h up to 5 mg/kg/d
Neonate: IM/IV 2.5 mg/kg q12–24h

Cystic Fibrosis
Adult/Child: IM/IV 2.5–3.5 mg/kg q6–8h Nebulized 300 mg inhaled b.i.d. times 28 d, may repeat after 28 d drug-free period

Administration

Note: All doses based on ideal body weight.

Instillation

Wash hands before and after instillation of eye medication. Apply gentle finger pressure to lacrimal sac (under inside of eyelid) for 1 min after drug has been instilled in eye.

Intramuscular

Give deep IM into a large muscle. Rotate injection sites.

Intravenous

Note: Verify correct IV concentration and rate of infusion to neonates, infants, or children with physician.

PREPARE: Intermittent: Dilute each dose in 50–100 mL or more of D5W, NS or D5/NS. Final concentration should not exceed 1 mg/mL.

ADMINISTER: Intermittent: Infuse diluted solution over 20–60 min.

INCOMPATIBILITIES Solution/additive: Alcohol 5% in dextrose, cephalosporins, penicillins, clindamycin, heparin. Y-site: Allopurinol, amphotericin B cholesteryl complex, azithromycin, cephalosporins, clindamycin, penicillins, heparin hetastarch, indomethacin, propofol, sargramostim.

Store at 15°–30° C (59°–86° F) prior to reconstitution. After reconstitution, solution may be refrigerated and used within 96 h. If kept at room temperature, use within 24 h.

Adverse Effects (1%)

CNS: Neurotoxicity (including ototoxicity), nephrotoxicity, increased AST, ALT, LDH, serum bilirubin; anemia, fever, rash, pruritus, urticaria, nausea, vomiting, headache, lethargy, superinfections; hypersensitivity. Special Senses: Burning, stinging of eye after drug instillation; lid itching and edema.

Interactions

Drug: anesthetics, skeletal muscle relaxants add to neuromuscular blocking effects; acyclovir, amphotericin B, bacitracin, capreomycin, cephalosporins, colistin, cisplatin, carboplatin, methoxyflurane, polymyxin B, vancomycin, furosemide, ethacrynic acid increased risk of ototoxicity, nephrotoxicity.

Pharmacokinetics

Peak: 30–90 min IM. Duration: Up to 8 h. Distribution: Crosses placenta; accumulates in renal cortex. Elimination: Excreted in urine. Half-Life: 2–3 h in adults.

Nursing Implications

Assessment & Drug Effects

Weigh patient before treatment for calculation of dosage.
Obtain bacterial C&S tests prior to and during therapy.
Observe patient receiving tobramycin closely because of the high potential for toxicity, even in conventional doses.
Lab tests: Baseline and periodic kidney function; monitor serum drug concentrations to minimize rise of toxicity. Prolonged peak serum concentrations >10 mcg/mL or trough concentrations >2 mcg/mL are not recommended.
Monitor auditory, and vestibular functions closely, particularly in patients with known or suspected renal impairment and patients receiving high doses.
Be aware that drug-induced auditory changes are irreversible (partial or total); usually bilateral. In cochlear damage, patient may be asymptomatic, and partial or bilateral deafness may continue to develop even after therapy discontinued.
Evidence of renal insufficiency, ototoxicity (see Appendix F), or vestibular damage indicates need for dosage adjustment or withdrawal of drug.
Monitor I&O. Report oliguria, changes in I&O ratio, and cloudy or frothy urine (may indicate proteinuria). Keep patient well hydrated to prevent chemical irritation in renal tubules; older adults are especially susceptible to renal toxicity.
Monitor patient with neuromuscular disorder (e.g., myasthenia gravis) for muscular weakness. Observe ambulation and assist if necessary.
Be aware that prolonged use of ophthalmic solution may encourage superinfection with nonsusceptible organisms including fungi.
Report overdose symptoms for eye medication: Increased lacrimation, keratitis, edema and itching of eyelids.

Patient & Family Education

Report symptoms of superinfections (see Appendix F) to physician. Prompt treatment with an antibiotic or antifungal medication may be necessary.
Report S&S of hearing loss, tinnitus, or vertigo to physician.
Do not breast feed while taking this drug without consulting physician.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug