gentamicin sulfate

gentamicin sulfate

(jen ta mye' sin)

Parenteral, intrathecal:

Alcomicin (CAN), Garamycin, Pediatric Gentamicin Sulfate

Topical dermatologic cream, ointment:

Garamycin

Ophthalmic:

Garamycin, Gentacidin, Gentak, Genoptic, Genoptic S.O.P.

Gentamicin impregnated PMMA beads:

Septopal

Gentamicin Liposome injection:

Maitec

Pregnancy Category D

Drug class

Aminoglycoside

Therapeutic actions

Bactericidal: Inhibits protein synthesis in susceptible strains of gram-negative bacteria; appears to disrupt functional integrity of bacterial cell membrane, causing cell death.

Indications

Parenteral

·        Serious infections caused by susceptible strains of Pseudomonas aeruginosa, Proteus species, Escherichia coli, Klebsiella-Enterobacter-Serratiaspecies, Citrobacter, Staphylococcus species

·        Serious infections when causative organisms are not known (often in conjunction with a penicillin or cephalosporin)

·        Unlabeled use: With clindamycin as alternative regimen in PID

Intrathecal

·        Gram-negative infections

·        Serious CNS infections, such as meningitis, ventriculitis, infections caused by susceptible Pseudomonas species

Ophthalmic preparations

·        Treatment of superficial ocular infections due to strains of microorganisms susceptible to gentamicin

Topical dermatologic preparation

·        Infection prophylaxis in minor skin abrasions and treatment of superficial infections of the skin due to susceptible organisms amenable to local treatment

Gentamicin-impregnated PMAA beads on surgical wire

·        Orphan drug use: Treatment of chronic osteomyelitis of posttraumatic, postoperative, or hematogenous origin

Gentamicin liposome injection

·        Orphan drug use: Treatment of disseminated Myobacterium avium-intracellulare infection

Contraindications and cautions

·        Contraindicated with allergy to any aminoglycosides.

·        Use cautiously with renal or hepatic disease; preexisting hearing loss; active infection with herpes, vaccinia, varicella, fungal infections, myobacterial infections (ophthalmic preparations); myasthenia gravis; parkinsonism; infant botulism; burn patients; lactation; pregnancy.

Available forms

Injection—10, 40 mg/mL; ophthalmic solution—3 mg/mL; ophthalmic ointment—3 mg/g; topical ointment—0.1%; topical cream—0.1%; ointment—1 mg; cream—1 mg

Dosages

Parenteral

ADULTS

3 mg/kg/day in three equal doses q 8 hr IM or IV. Up to 5 mg/kg/day in three to four equal doses in severe infections. For IV use, a loading dose of 1–2 mg/kg may be infused over 30–60 min, followed by a maintenance dose, usually for 7–10 days.

·        PID: 2 mg/kg IV followed by 1.5 mg/kg tid plus clindamycin 600 mg IV qid. Continue for at least 4 days and at least 48 hr after patient improves, then continue clindamycin 450 mg orally qid for 10–14 days total therapy.

·        Surgical prophylaxis regimens: Several complex, multidrug prophylaxis regimens are available for preoperative use; consult manufacturer's instructions.

PEDIATRIC PATIENTS

2–2.5 mg/kg q 8 hr IM or IV.

Infants and neonates: 2.5 mg/kg q 8 hr.

Premature or full-term neonates: 2.5 mg/kg q 12 hr.

GERIATRIC PATIENTS OR PATIENTS WITH RENAL FAILURE

Reduce dosage or extend time dosage intervals, and carefully monitor serum drug levels and renal function tests.

Ophthalmic solution

ADULTS AND PEDIATRIC PATIENTS

1–2 drops into affected eye or eyes q 4 hr; use up to 2 drops hourly in severe infections.

Ophthalmic ointment

ADULTS AND PEDIATRIC PATIENTS

Apply small amount to affected eye bid–tid.

Dermatologic preparations

ADULTS AND PEDIATRIC PATIENTS

Apply tid to qid. Cover with sterile bandage if needed.

Pharmacokinetics

Route	Onset	Peak
IM, IV	Rapid	30–90 min

Metabolism: Hepatic; T_1/2: 2–3 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Urine

IV facts

Preparation: Dilute single dose in 50–200 mL of sterile isotonic saline or D₅W. Do not mix in solution with any other drugs.

Infusion: Infuse over 30–120 min.

Incompatibilities: Do not mix in solution with any other drugs.

Adverse effects

·        CNS: Ototoxicity—tinnitus, dizziness, vertigo, deafness (partially reversible to irreversible), vestibular paralysis, confusion, disorientation, depression, lethargy, nystagmus, visual disturbances, headache, numbness, tingling, tremor, paresthesias, muscle twitching, seizures, muscular weakness, neuromuscular blockade

·        CV: Palpitations, hypotension, hypertension

·        GI: Hepatic toxicity, nausea, vomiting, anorexia, weight loss, stomatitis, increased salivation

·        GU: Nephrotoxicity

·        Hematologic: Leukemoid reaction, agranulocytosis, granulocytosis, leukopenia, leukocytosis, thrombocytopenia, eosinophilia, pancytopenia, anemia, hemolytic anemia, increased or decreased reticulocyte count, electrolyte disturbances

·        Hypersensitivity: Purpura, rash, urticaria, exfoliative dermatitis, itching

·        Local: Pain, irritation, arachnoiditis at IM injection sites

·        Other: Fever, apnea, splenomegaly, joint pain, superinfections

Ophthalmic preparations

·        Local: Transient irritation, burning, stinging, itching, angioneurotic edema, urticaria, vesicular and maculopapular dermatitis

Topical dermatologic preparations

·        Local: Photosensitization, superinfections

Interactions

Drug-drug

·        Increased ototoxic, nephrotoxic, neurotoxic effects with other aminoglycosides, cephalothin, potent diuretics, cephalosporins, vancomycin, methoxyflurane, enflurane

·        Increased neuromuscular blockade and muscular paralysis with anesthetics, nondepolarizing neuromuscular blocking drugs, succinylcholine, citrate-anticoagulated blood

·        Potential inactivation of both drugs if mixed with beta-lactam–type antibiotics (space doses with concomitant therapy)

·        Increased bactericidal effect with penicillins, cephalosporins (to treat some gram-negative organisms and enterococci), carbenicillin, ticarcillin (to treatPseudomonas infections)

Nursing considerations

Assessment

·        History: Allergy to any aminoglycosides; renal or hepatic disease; preexisting hearing loss; active infection with herpes, vaccinia, varicella, fungal infections,myobacterial infections (ophthalmic preparations); myasthenia gravis; parkinsonism; infant botulism; lactation, pregnancy

·        Physical: Site of infection; skin color, lesions; orientation, reflexes, eighth cranial nerve function; P, BP; R, adventitious sounds; bowel sounds, liver evaluation; urinalysis, BUN, serum creatinine, serum electrolytes, LFTs, CBC

Interventions

·        Give by IM route if at all possible; give by deep IM injection.

·        Culture infected area before therapy.

·        Use 2 mg/mL intrathecal preparation without preservatives, for intrathecal use.

·        Avoid long-term therapies because of increased risk of toxicities. Reduction in dose may be clinically indicated.

·        Patients with edema or ascites may have lower peak concentrations due to expanded extracellular fluid volume.

·        Cleanse area before application of dermatologic preparations.

·        Ensure adequate hydration of patient before and during therapy.

·        WARNING: Monitor renal function tests, CBCs, serum drug levels during long-term therapy. Consult with prescriber to adjust dosage.

Teaching points

·        Apply ophthalmic preparations by tilting head back; place medications into conjunctival sac and close eye; apply light pressure on lacrimal sac for 1 minute. Cleanse area before applying dermatologic preparations; area may be covered if necessary.

·        You may experience these side effects: Ringing in the ears, headache, dizziness (reversible; use safety measures if severe); nausea, vomiting, loss of appetite (eat frequent small meals, perform frequent mouth care); burning, blurring of vision with ophthalmic preparations (avoid driving or performing dangerous activities if visual effects occur); photosensitization with dermatologic preparations (wear sunscreen and protective clothing).

·        Report pain at injection site, severe headache, dizziness, loss of hearing, changes in urine pattern, difficulty breathing, rash or skin lesions; itching or irritation (ophthalmic preparations); worsening of the condition, rash, irritation (dermatologic preparation).

Adverse effects in Italic are most common; those in Bold are life-threatening.