Gentamicin

A to Z Drug Facts

(JEN-tuh-MY-sin)

Garamycin, Gentak, Genoptic, Genoptic S.O.P., Gentacidin, G-myticin,  Alcomicin, Cidomycin, Diogent, Garatec, Gent-AK, Minims, Gentamicin, Ocugram, Ophthagram, PMS-Gentamicin Sulfate, Scheinpharm Gentamicin

Class: Antibiotic/Aminoglycoside

 Action Inhibits production of bacterial protein, causing bacterial cell death

 Indications Short-term treatment of serious infections caused by susceptible strains of microorganisms, especially gram-negative bacteria; adjunct to systemic gentamicin in serious CNS infections (intrathecal); treatment of superficial ocular infections (ophthalmic); treatment of superficial skin infections, infection prophylaxis and aid to healing (topical).

 Contraindications Long-term therapy (parenteral); epithelial herpes simplex keratitis, vaccinia, varicella, mycobacterial infections, fungal diseases (ophthalmic); hypersensitivity to aminoglycosides.

 Route/Dosage

ADULTS: IM/IV 3 to 5 mg/kg/day in divided doses. For obese patients, base dose on estimate of lean body weight. CHILDREN: IM/IV 6 to 7.5 mg/kg/day (2 to 2.5 mg/kg q 8 hr). INFANTS & NEONATES: IM/IV 7.5 mg/kg/day (2.5 mg/kg q 8 hr). PREMATURE OR TERM NEONATES (< 1 wk): IM/IV 5 mg/kg/day (2.5 mg/kg q 12 hr) or 2.5 mg/kg q 18 hr or 3 mg/kg q 24 hr.

Prevention of Bacterial Endocarditis

ADULTS: IM/IV 1.5 mg/kg with ampicillin ½ hr before procedure (maximum 80 mg). CHILDREN: IM/IV 2 mg/kg with ampicillin ½ hr before procedure.

Superficial Skin Infections

ADULTS & CHILDREN: Topical Apply 1 to 4 times daily to infected area.

Ocular Infections

ADULTS & CHILDREN: Topical Apply 0.5-inch ribbon of ointment in each eye bid or tid or 1 to 2 gtt 4 to 6 times/day.

 Interactions

Drugs with nephrotoxic potential (eg, amphotericin, cephalosporins, enflurane, methoxyflurane, vancomycin): May increase risk of nephrotoxicity. Loop diuretics: May increase risk of auditory toxicity. Neuromuscular blocking agents: May enhance effects of these agents. Polypeptide antibiotics: May increase risk of respiratory paralysis and renal dysfunction. INCOMPATIBILITIES: Do not mix beta-lactam antibiotics (eg, penicillins, especially ticarcillin and carbenicillin, cephalosporins) in IV solutions.

 Lab Test Interferences None well documented.

 Adverse Reactions

CNS: Headache; dizziness; vertigo; encephalopathy; confusion; fever; lethargy; convulsions; muscle weakness and twitching; peripheral neuropathy; acute organic brain syndrome; depression; pseudotumor cerebri; increased CSF protein; arachnoiditis or burning at injection site after intrathecal administration. DERM: Rash; urticaria; itching; anaphylaxis; photosensitivity (topical). EENT: Blurred vision; tinnitus; hearing loss; mydriasis and conjunctival paresthesia (ophthalmic). GI: Nausea; vomiting. GU: Oliguria; proteinuria; increased serum creatinine and BUN; casts; Fanconi-like syndrome. HEMA: Anemia; eosinophilia; leukopenia; thrombocytopenia; granulocytopenia. HEPA: Elevated liver function test results. RESP: Apnea; pulmonary fibrosis. OTHER: Pain and irritation at injection site; splenomegaly; hypomagnesemia; hyponatremia; hypocalcemia; hypokalemia.

 Precautions

Pregnancy: Category D (parenteral). Category C (ophthalmic). Lactation: Undetermined. Children: Use cautiously in premature infants and neonates because of renal immaturity. Elderly or debilitated patients: Drug levels and renal function must be monitored closely. Burn patients: Pharmacokinetics may be altered; serum levels must be closely monitored for dosing. Hypomagnesemia: Occurs often, especially in those with restricted diets or poor nutrition. Neuromuscular blockade: Potential curare-like effects may aggravate muscle weakness or cause neurotoxicity. Use with caution with anesthesia or muscle relaxants; in patients with neuromuscular disorders, hypomagnesemia, hypocalcemia and hypokalemia; and in neonates whose mothers received magnesium sulfate. Sulfite sensitivity: Some products contain sulfites. Do not use if there is history of hypersensitivity. Toxicity: Drug is associated with significant nephrotoxicity and ototoxicity. Use with particular caution in patients with renal impairment and elderly patients.

 Administration/Storage

• Do not premix with any other drugs; administer separately.
• For topical use, cleanse affected area of skin before applying ointment.
• For ophthalmic use, have patient tilt head back, place medication in conjunctival sac, and instruct patient to close eyes. Apply light finger pressure on lacrimal sac for 1 min after instillation.
• Store at room temperature.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies. Note sulfite sensitivity.
• Monitor renal function (serum creatinine, BUN, creatinine clearance) and 8th cranial nerve function.
• Peak and trough levels should be evaluated within 48 hr after initiating therapy and then q 3 to 4 days.
• If culture and sensitivity is ordered, obtain specimen prior to administration of drug.
• Keep patient well hydrated and monitor serum electrolytes.
• Withhold drug and notify health care provider if any of following symptoms occur: Decreased urinary output, headache, dizziness, confusion, tinnitus, vertigo, hearing loss, vaginal itching, or discharge.

 Patient/Family Education

• With parenteral administration, instruct patient to report any changes in urinary output (decreased), hearing (ringing in ears, hearing loss), dizziness, tingling or numbness in hands and feet, growth on tongue, and vaginal itch or discharge.
• For topical application, instruct patient to cleanse affected area of skin prior to application and to notify health care provider if rash or irritation develops or if condition worsens.
• For ophthalmic use, instruct patient in proper technique for instilling drops or ointment, emphasizing importance of avoiding contact between dispensing container and eyes. Inform patient that drug may cause temporary blurring of vision or stinging after administration. Advise patient to notify health care provider if stinging, itching, or burning increase or if irritation or pain persists. Discard remaining ophthalmic preparation after completion of therapy.
• Instruct patient to continue using medication for prescribed time, even after signs and symptoms have been relieved, to prevent recurrence.
• Caution patient to avoid exposure to sunlight and to use sunscreen or wear protective clothing to avoid photosensitivity reaction.

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