Tobramycin

A to Z Drug Facts

(TOE-bruh-MY-sin)

Nebcin, TOBI, Tobrex,  Scheinpharm Tobramycin

Class: Antibiotic/aminoglycoside

 Action Inhibits bacterial protein synthesis, causing cell death.

 Indications Treatment of serious infections caused by susceptible strains of gram-negative bacteria; treatment of serious susceptible staphylococcal infections when other, less toxic drugs are contraindicated. Ophthalmic use: Treatment of superficial ocular infections. Management of cystic fibrosis patients with Pseudomonas aeruginosa.

 Contraindications Previous reactions to aminoglycosides. Ophthalmic use: Epithelial herpes simplex keratitis; vaccinia; varicella; mycobacterial infections of eye; fungal infections.

 Route/Dosage

ADULTS: IM/IV 3–5 mg/kg/day in 3–4 equal doses. Ophthalmic 1.25 cm ribbon of ointment bid-tid (q 3–4 hr for severe infections) or 1–2 gtt 4–6 times/day (for severe infections, q hr until improvement; then frequency of administration is reduced). CHILDREN: IM/IV 6–7.5 mg/kg/day in 3–4 equally divided doses. Ophthalmic 1.25 cm ribbon of ointment bid-tid (q 3–4 hr for severe infections) or 1–2 gtt 4–6 times/day (for severe infections, q hr until improvement; then frequency of administration is reduced). PREMATURE OR FULL-TERM NEONATES £ 1 WK: IM/IV Up to 4 mg/kg/day in 2 divided doses.

 Interactions

Depolarizing and nondepolarizing muscle relaxants: May enhance neuromuscular blocking effects. Protracted respiratory depression may occur. Loop diuretics: May increase auditory toxicity. Nephrotoxic drugs (eg, amphotericin B, cephalosporins, enflurane, methoxyflurane, vancomycin): May increase risk of nephrotoxicity. Penicillins: Penicillins, particularly carbenicillin and ticarcillin, can inactivate tobramycin in admixture, assay procedures, or patients with renal failure. Polypeptide antibiotics: May increase risk of respiratory paralysis and renal dysfunction. INCOMPATIBILITIES: Do not mix with other drugs.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Headache; fever; confusion; lethargy; disorientation; delirium. DERM: Rash; urticaria; itching; pain and irritation at injection site. EENT: Tinnitus; vertigo; dizziness; hearing loss. With ophthalmic preparation: ocalized ocular toxicity and hypersensitivity; lid itching; lid swelling; onjunctival erythema. GI: Nausea; vomiting; diarrhea. GU: Oliguria; proteinuria; increased serum creatinine and BUN. HEMA: Anemia; leukopenia; leukocytosis; eosinophilia. META: Decreased serum calcium, sodium, potassium, or magnesium; increased LFT results. RESP: Apnea.

 Precautions

Pregnancy: Category D (parenteral); Category B (ophthalmic). Lactation: Undetermined. Children: Use parenteral form cautiously in premature infants and neonates due to renal immaturity. Burn patients: Pharmacokinetics may be altered; serum levels are important for determining appropriate dosing. Hypomagnesia: Occurs often, especially in those with restricted diets or who eat poorly. Long-term therapy: Generally not indicated; greatly increases risk of toxic reactions. Neuromuscular blockade: Potential curare-like effects may aggravate muscle weakness or cause neurotoxicity. Use drug with caution in patients with neuromuscular disorders, hypomagnesemia, hypocalcemia or hypokalemia; with anesthesia or muscle relaxants, and in neonates whose mothers received magnesium sulfate. Ophthalmic ointment: May retard corneal healing. Toxicity: Drug is associated with significant nephrotoxicity and ototoxicity (both auditory and vestibular). Use drug with particular caution in patients with renal impairment or previous hearing loss and in elderly patients.

 Administration/Storage

• Administer separately. Do not mix with other drugs.
• For intravenous administration dilute in 50–100 ml of 0.9% odium Chloride Injection or 5% Dextrose Injection. Use less diluent for children. Administer over ³ 20 min-60 min.
• Administer IM injection deep into large muscle.
• For ophthalmic preparations, wash hands before and after instillation. Have patient tilt head back; place medication in conjunctival sac and have patient close eyes. Apply light finger pressure on lacrimal duct for 1 min following instillation. Do not touch tip of container to any surface.
• Store ophthalmic preparations at room temperature away from sunlight. Do not freeze.
• Discard if solution is brown or cloudy or contains particles.

Nebulizer solution

• Do not adjust dosage by age or weight.
• Administer as close to 12 hours apart as possible. Do not administer < 6 hours apart.
• Administer by inhalation over 10 to 15 minute period.
• Do not dilute or mix with dornase alfa in the nebulizer.

 Assessment/Interventions

• Obtain culture and susceptibility before initiating drug therapy. Treatment can be initiated before results are obtained.
• Obtain patient history, including drug history and any known allergies. Determine if patient has renal impairment, hearing loss, neuromuscular disorders, muscle weakness, Parkinson's disease, myasthenia gravis, mycobacterial infections or fungal infections.
• If patient may be intubated or ventilated, inform anesthetist that patient is taking this drug. Neuromuscular effects may be enhanced with succinylcholine or other neuromuscular blocking agent.
• Do not administer to neonates if mother received magnesium sulfate.
• Monitor and record respiratory status.
• Schedule hearing test prior to administration. Periodically test hearing throughout treatment and 1 mo after treatment is discontinued. Deafness may occur after drug has been discontinued, especially if treated > 10 days.
• Monitor renal function (especially in elderly patients), creatinine clearance rate and BUN. Report any changes from baseline to physician.
• Request periodic urine studies.
• Monitor peak and trough drug levels, especially in elderly patients, and use to guide dosing. Obtain these values within 48 hr of start of therapy and every 3–4 days.
• Monitor for signs of superinfection.
• Monitor I&O and report imbalances to physician.
• Monitor magnesium, sodium, calcium and potassium blood levels. Report low levels to physician.
• Monitor neurologic status and function of cranial nerve VIII. Report tinnitus, vertigo, numbness, tingling, muscle twitching or weakness and convulsions to physician.
• Keep patient well hydrated.
• If toxicity is detected, immediately notify physician. Discontinuation of drug or adjustment of dose or dosing interval may be required.

 Patient/Family Education

• Instruct patient how to administer ophthalmic preparation, including need for careful handwashing.
• Encourage patient to drink plenty of fluids while taking drug.
• Instruct patient to notify physician of headache, fever, confusion, nausea, vomiting, diarrhea, rashes, itching, pain at injection site, ringing or roaring in ears, dizziness or hearing loss.
• Advise patient to consult with physician before taking any other otc or prescription medications.
• Inform patient that physician will want follow-up blood studies and audiograms.
• Inform patient that ophthalmic preparations may cause temporary blurring of vision or stinging and instruct patient to report excessive stinging, burning, persistent or increased pain, tearing, lid itching, swelling or redness of eyes to physician.
• Instruct patient not to wear contact lenses during treatment.
• For patient using ophthalmic solution, stress need for compliance with complete course of therapy.

Nebulizer solution

• Instruct patient to take as close to 12 hours apart as possible. Do not take < 6 hours apart.
• Should be taken over a 10 to 15 minute period using a hand-held PARI LC PLUS reusable nebulizer with a DeVilbiss Pulmo-Aide compressor.
• If patient is on multiple therapies, other therapies should be taken first followed by tobramycin.
• Inhale while sitting or standing upright and breathing normally through the mouthpiece of the nebulizer. Nose clips may help the patient breathe through the mouth.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts