GENTAMICIN SULFATE 
(jen-ta-mye'sin)
Garamycin, Garamycin Ophthalmic, Genoptic
Classifications: antiinfective; aminoglycoside antibiotic
Pregnancy Category: C
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10 mg/mL, 40 mg/mL; 0.1% ointment, cream; 3 mg/mL ophthalmic solution; 3 mg/g ophthalmic ointment
Broad-spectrum aminoglycoside antibiotic derived from Micromonospora purpurea.
Active against a wide variety of gram-negative bacteria, including Escherichia coli, Enterobacter, Klebsiella, Proteus, Pseudomonas aeruginosa, and Serratia sp. Also effective against certain gram-positive organisms, particularly penicillin-sensitive and some methicillin-resistant
strains of Staphylococcus aureus (MRSA).
Parenteral use restricted to treatment of serious infections of GI, respiratory, and urinary tracts, CNS, bone, skin, and
soft tissue (including burns) when other less toxic antimicrobial agents are ineffective or are contraindicated. Has been
used in combination with other antibiotics. Also used topically for primary and secondary skin infections and for superficial
infections of external eye and its adnexa.
Prophylaxis of bacterial endocarditis in patients undergoing operative procedures or instrumentation.
History of hypersensitivity to or toxic reaction with any aminoglycoside antibiotic. Safe use during pregnancy (category C)
or lactation is not established.
Impaired renal function; history of eighth cranial (acoustic) nerve impairment; preexisting vertigo or dizziness or tinnitus;
dehydration, fever; use in older adults, premature infants, neonates, and infants; obesity, neuromuscular disorders: myasthenia
gravis, parkinsonian syndrome; hypocalcemia, heart failure, topical applications to widespread areas.
Moderate to Severe Infection
Adult: IV/IM 1.5–2 mg/kg loading dose followed by 3–5 mg/kg/d in 2–3 divided doses Intrathecal 4–8 mg preservative free q.d. Topical 1–2 drops of solution in eye q4h up to 2 drops q1h or small amount of ointment b.i.d. or t.i.d.
Child: IV/IM 6–7.5 mg/kg/d in 3–4 divided doses Intrathecal >3 mo, 1–2 mg preservative free q.d.
Neonate: IV/IM 2.5 mg/kg q12–24h
Acute Pelvic Inflammatory Disease
Adult: IV/IM 2 mg/kg followed by 1.5 mg/kg q8h
Prophylaxis of Bacterial Endocarditis
Adult: IV/IM 1.5 mg/kg 30 min before procedure, may repeat in 8 h
Child: IV/IM < 27 kg, 2 mg/kg 30 min before procedure, may repeat in 8 h
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Ophthalmic
- Apply pressure to inner canthus for 1 min immediately after instillation of drops.
- Have patient keep eyes closed for 1–2 min after administration of ophthalmic ointment to assure medication contact. Caution
patient that vision will be blurred for a few minutes.
Topical
- Wash affected area with mild soap and water, rinse, and dry thoroughly. Gently apply small amount of medication to lesions;
cover with sterile gauze.
- Do not apply topical preparations, particularly cream, to large denuded body surfaces because systemic absorption and toxicity
are possible.
Intramuscular
- Give deep into a large muscle.
- Do not use solutions that are discolored or that contain particulate matter; drug for IV or IM is clear and colorless or slightly
yellow.
Intrathecal
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Note: Intrathecal formulation is a clear and colorless solution.
- Use promptly after opening; contains no preservatives and any unused portion should be discarded.
| Intravenous PREPARE: Intermittent: Dilute a single dose with 50–200 mL of D5W or NS. For pediatric patients, amount of infusion fluid may be proportionately
smaller depending on patient's needs but should be sufficient to be infused over the same time period as for adults.
ADMINISTER: Intermittent: Give over 30 min–2 h.
INCOMPATIBILITIES Solution/additive: Fat emulsion, tpn, amphotericin B,
ampicillin,
carbenicillin,
cephalosporins, cytarabine,
heparin.
Y-site:
Azithromycin, furosemide,
iodipamide.
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- Store all gentamicin solutions between 2°–30° C (36°–86° F) unless otherwise directed by manufacturer.
Special Senses: Ototoxicity (vestibular disturbances, impaired hearing), optic neuritis. CNS: neuromuscular blockade: skeletal muscle weakness, apnea, respiratory paralysis (high doses); arachnoiditis (intrathecal use). CV: hypotension or hypertension. GI: Nausea, vomiting, transient increase in AST, ALT, and serum LDH and bilirubin; hepatomegaly, splenomegaly. Hematologic: Increased or decreased reticulocyte counts; granulocytopenia, thrombocytopenia (fever, bleeding tendency), thrombocytopenic
purpura, anemia. Body as a Whole: Hypersensitivity (rash, pruritus, urticaria, exfoliative dermatitis, eosinophilia, burning sensation of skin, drug fever,
joint pains, laryngeal edema, anaphylaxis). Urogenital:
Nephrotoxicity: proteinuria, tubular necrosis, cells or casts in urine, hematuria, rising BUN, nonprotein nitrogen, serum creatinine; decreased creatinine clearance.
Other: Local irritation and pain following IM use; thrombophlebitis, abscess, superinfections, syndrome of hypocalcemia (tetany,
weakness, hypokalemia, hypomagnesemia). Topical and Ophthalmic: Photosensitivity, sensitization, erythema, pruritus; burning, stinging, and lacrimation (ophthalmic formulation).
Drug:
Amphotericin B,
capreomycin,
cisplatin,
methoxyflurane,
polymyxin B,
vancomycin,
increase risk of nephrotoxicity.
Ethacrynic acid and furosemide may increase risk of ototoxicity. general anesthetics and neuromuscular blocking agents (e.g., succinylcholine) potentiate neuromuscular blockade. Indomethacin may increase gentamicin levels in neonates.
Absorption: Well absorbed from IM site. Peak: 30–90 min IM. Distribution: Widely distributed in body fluids, including ascitic, peritoneal, pleural, synovial, and abscess fluids; poor CNS penetration;
concentrates in kidney and inner ear; crosses placenta. Metabolism: Not metabolized. Elimination: Excreted unchanged in urine; small amounts accumulate in kidney and are eliminated over 10–20 d; small amount excreted
in breast milk. Half-Life: 2–4 h.
Assessment & Drug Effects
- Lab tests: Perform C&S and renal function prior to first dose and periodically during therapy; therapy may begin pending test
results. Determine creatinine clearance and serum drug concentrations at frequent intervals, particularly for patients with
impaired renal function, infants (renal immaturity), older adults, patients receiving high doses or therapy beyond 10 d, patients
with fever or extensive burns, edema, obesity.
- Repeat C&S if improvement does not occur in 3–5 d; reevaluate therapy.
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Note: Dosages are generally adjusted to maintain peak serum gentamicin concentrations of 4– 10 g/mL, and trough concentrations
of 1–2 g/mL. Peak concentrations above 12 g/mL and trough concentrations above 2 g/mL are associated with toxicity.
- Draw blood specimens for peak serum gentamicin concentration 30 min–1h after IM administration, and 30 min after completion
of a 30–60 min IV infusion. Draw blood specimens for trough levels just before the next IM or IV dose. Use nonheparinized
tubes to collect blood.
- Check baseline weight and vital signs; determine vestibular and auditory function before therapy and at regular intervals.
Check vestibular and auditory function again 3–4 wk after drug is discontinued (the time that deafness is most likely
to occur).
- Monitor I&O. Keep patient well hydrated to prevent chemical irritation of renal tubules. Report oliguria, unusual appearance
of urine, change in I&O ratio or pattern, and presence of edema (prolongs elimination time).
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Note: Ototoxic effect (see Appendix F) is greatest on the vestibular branch of eighth cranial (acoustic) nerve (symptoms: headache,
dizziness or vertigo, nausea and vomiting with motion, ataxia, nystagmus). However, damage to the auditory branch (tinnitus,
roaring noises, sensation of fullness in ears, hearing impairment) may also occur. Report promptly to prevent permanent damage.
- Watch for S&S of bacterial overgrowth (opportunistic infections) with resistant or nonsusceptible organisms (diarrhea, anogenital
itching, vaginal discharge, stomatitis, glossitis).
Patient & Family Education
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Note: When using topical applications: Avoid excessive exposure to sunlight because of danger of photosensitivity; withhold medication
and notify physician if condition fails to improve within 1 wk, worsens, or signs of irritation or sensitivity occur; and
apply medication as directed and only for length of time prescribed (overuse can result in superinfections).
- Do not breast feed while taking this drug without consulting physician.
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Canadian drug name;