Gentamicin

Indications

Gentamicin is used for: Pneumonia, Cystic fibrosis, Meningitis, Peritonitis, Endocarditis, Susceptible infections, Septicaemia, Pelvic inflammatory disease, Endometritis, Biliary tract infections, Granuloma inguinale, Listeriosis, Gastroenteritis, Plague, Cat scratch disease, Brucellosis, Otitis externa, Surgical infections, Skin infections.

Adult Dose

Parenteral Susceptible Infections Adult: 3-5 mg/kg daily in divided doses 8 hourly for 7-10 days, by IM or slow IV inj over 2-3 min or IV infusion over no more than 20-30 min. Surgical Infection Prophylaxis Oral/pharyngeal: 1.5 mg/kg IV PLUS clindamycin 600-900 mg IV Ruptured viscus: 1.5 mg/kg IV q8hr PLUS clindamycin 600 mg IV q6hr Endocarditis Prophylaxis GI, GU procedure: 1.5 mg/kg IV/IM <30 minutes before procedure PLUS ampicillin or vancomycin Cystic Fibrosis 7.5-10.5 mg/kg/day IV/IM divided q8hr Pelvic Inflammatory Disease Loading dose: 2 mg/kg IV or IM Maintenance dose: 1.5 mg/kg IV or IM q8hr

Child Dose

Pediatric IV, IM 3–7.5 mg/kg/day (cystic fibrosis 7–10); q8h Up to 2 weeks: 3 mg/kg/every 12 hours 2 weeks to 12 years: 2 mg/kg/every 8 hours

Renal Dose

Renal impairment CrCl >90 mL/min and <60 years: q8hr CrCl 60-90 mL/min or ?60 years: q12hr CrCl 25-60 mL/min: q24hr CrCl 10-25 mL/min: q48hr CrCl <10 mL/min: q72hr Following dialysis in ESRD

Administration

IV Preparation Dilute single dose in 50-200 mL NS or D5W IV Administration Infuse over 30 min-2 hr After infusion, flush line with NS or D5W

Contra Indications

History of hypersensitivity to aminoglycoside; pregnancy; hepatic impairment, perforated ear drum.

Precautions

History of hypersensitivity to aminoglycoside; pregnancy; hepatic impairment, perforated ear drum. Lactation: Enters breast milk; use with caution (AAP Committee states "compatible with nursing")

Pregnancy-Lactation

Pregnancy category: D Lactation: Enters breast milk; use with caution (AAP Committee states "compatible with nursing")

Interactions

Synergistic with ampicillin, benzylpenicillin and other beta-lactam antibiotics. Increased risk of severe respiratory depression when used concurrently with anaesthetics or opioids. May reduce renal clearance of zalcitabine and induce hypocalcaemia when used with biphosphonates. Not to be used with agalsidase alfa or beta as it may inhibit alpha-galactosidase activity. Potentially Fatal: Increased incidence of ototoxicity when combined with ethacrynic acid and furosemide. Cephalosporins, ciclosporin, cisplatin, vancomycin, hydrocortisone and indometacin potentiate nephrotoxicity. Potentiates neuromuscular blocking agents.

Side Effects

Side effects of Gentamicin : >10% Neurotoxicity (vertigo, ataxia), Gait instability, Ototoxicity (auditory, vestibular), Nephrotoxicity (decreased CrCl), Nephrotoxicity if trough >2 mg/L 1-10% Edema, Rash, Reddening of skin, Itching <1% Drowsiness, Headache, Pseudomotor cerebri, Photosensitivity, Allergic reaction, Erythema, Anorexia, Nausea/vomiting, Weight loss, Increased salivation, Enterocolitis, Granulocytopenia, Agranulocytosis, Thrombocytopenia, Elevated LFT Burning, Stinging, Tremors, Muscle cramps, Weakness, Dyspnea Potentially Fatal: Nephrotoxicity, ototoxicity and neuromuscular blockade (may unmask or aggravate myasthaenia gravis).

Mode of Action

Gentamicin is an aminoglycoside that binds to 30s and 50s ribosomal subunits of susceptible bacteria disrupting protein synthesis, thus rendering the bacterial cell membrane defective.