TOBRAMYCIN SULFATE

TOBRAMYCIN SULFATE
(toe-bra-mye'sin)
AKTob, TobraDex, Tobrex, TOBI
Classifications: aminoglycoside antibiotic;
Therapeutic: antibiotic

Prototype: Gentamicin sulfate
Pregnancy Category: D

Availability

10 mg/mL, 40 mg/mL injection; 300 mg/5 mL inhalation solution; 0.1%, 0.3% ophthalmic solution; 0.1%, 0.3% ophthalmic ointment

Action

Broad-spectrum, aminoglycoside antibiotic derived from Streptomyces tenebrarius. Tobramycin binds irreversibly to one of two aminoglycoside binding sites on the 30S ribosomal subunit of the bacteria, thus inhibiting protein synthesis, resulting in bacterial cell death.

Therapeutic Effect

Effective in treatment of gram-negative bacteria. 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; pregnancy (category D).

Cautious Use

Impaired kidney function; renal disease; dehydration; hearing impairment; myasthenia gravis; parkinsonism; concurrent use with other neurotoxic or nephrotoxic agents or potent diuretics; premature and neonatal infants; older adults; lactation.

Route & Dosage

Moderate to Severe Infections
Adult: IV/IM 3 mg/kg/d divided q8h up to 5 mg/kg/d OR 4–7 mg/kg/d single dose Topical 1–2 drops in affected eye q1–4h
Child: IM/IV <5 y, 2.5 mg/kg q8h IV/IM ≥5 y, 2–2.5 mg/kg/d divided q8h
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. x 28 d, may repeat after 28 d drug-free period

Renal Impairment
Increase interval.
Hemodialysis: Administer dose after dialysis and monitor levels

Obesity
Dose based on IBW; in morbid obesity, use dosing weight of IBW + 0.4 (Weight – IBW).

Administration

Note: All doses should be 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. Avoid rapid infusion.  

INCOMPATIBILITIES Solution/additive: Alcohol 5% in dextrose, cefamandole, cefepime, cefoperazone, cefoxitin, clindamycin, heparin. Y-site: Allopurinol, amphotericin B cholesteryl complex, azithromycin, cefoperazone, 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: 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.

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

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