What are the indications, contraindications, side effects, drug interactions, and off‑label uses of injectable amikacin 500 mg in India?

INDICATION OF INJ AMIKACIN 500 MG AND CONTRAINDICATION, SIDE EFFECT, DRUG INTERACTION AND OFF LABEL USAGE IN INDIA

Injectable amikacin 500 mg is indicated for serious Gram-negative bacterial infections including Pseudomonas, E. coli, Klebsiella, and other susceptible organisms, and as a second-line agent for drug-resistant tuberculosis. 1

INDICATIONS

FDA-Approved (On-Label) Uses

Amikacin is indicated for short-term treatment of serious infections caused by susceptible Gram-negative bacteria 1:

• Pseudomonas species
• Escherichia coli
• Proteus species (indole-positive and indole-negative)
• Providencia species
• Klebsiella species
• Enterobacter species
• Serratia species
• Acinetobacter species

Off-Label Uses

Drug-Resistant Tuberculosis (Most Important Off-Label Use)

Amikacin is a second-line injectable drug for MDR-TB and XDR-TB 2:

Dosing for TB:

• Adults: 15 mg/kg/day (maximum 1.0 g/day) IM or IV, given as single daily dose 5-7 days/week initially, then reducing to 2-3 times weekly after first 2-4 months or after culture conversion 2
• Elderly (>59 years): Reduce to 10 mg/kg/day (750 mg) 2
• Children: 15-30 mg/kg/day (maximum 1 g/day) as single daily dose 2

Amikacin demonstrates superior efficacy compared to other injectable agents for MDR-TB, with increased treatment success rates (aOR 1.7; 95% CI 1.3-2.2) and reduced mortality in XDR-TB (aOR 0.4; 95% CI 0.2-0.8) 3.

Other Off-Label Uses:

• Carbapenem-resistant Enterobacterales (CRE): 15 mg/kg/day IV once daily for complicated UTIs 4
• Non-tuberculous mycobacterial infections (particularly MAC-PD) 5
• Obstetric/gynecologic infections 6
• Urinary tract infections in cancer patients 7

CONTRAINDICATIONS

Absolute Contraindications 1:

• Hypersensitivity to amikacin
• History of hypersensitivity or serious toxic reactions to any aminoglycoside (due to known cross-sensitivity)
• Pregnancy - contraindicated due to risk of fetal nephrotoxicity and congenital hearing loss 2

Relative Contraindications/Use with Extreme Caution 1:

• Myasthenia gravis - may aggravate muscle weakness due to curare-like effect on neuromuscular junction
• Parkinson's disease - may worsen muscle weakness

SIDE EFFECTS

Major Toxicities (Life-Altering)

Ototoxicity 2:

• Hearing loss (cochlear toxicity): 1.5-24% incidence, with higher rates in longer treatment/higher doses
• Less vestibular dysfunction compared to streptomycin
• Risk increased with: Concurrent loop diuretics (furosemide, ethacrynic acid), longer duration, higher cumulative doses
• Often irreversible and may progress even after drug discontinuation 3

Nephrotoxicity 2:

• More nephrotoxic than streptomycin 2
• 8.7% overall incidence of renal impairment
• 3.4% in patients without risk factors
• Higher risk with: Pre-existing elevated creatinine, larger total doses, concurrent nephrotoxic agents (especially vancomycin, capreomycin, cephalosporins, ciclosporin, colistin, tacrolimus) 5, 8
• Often reversible if caught early 3

Other Adverse Effects 1:

• Neuromuscular blockade (rare but potentially fatal)
• Electrolyte disturbances 3
• Overgrowth of nonsusceptible organisms
• Diarrhea (antibiotic-associated)

Monitoring Requirements 2:

Baseline:

• Audiogram
• Vestibular testing
• Romberg testing
• Serum creatinine

During Treatment:

• Monthly: Renal function assessment, questioning about auditory/vestibular symptoms
• Serum drug concentration monitoring (advantage of amikacin over other aminoglycosides) 2
• Repeat audiogram/vestibular testing if symptoms develop
• Trough levels: Target <5 mg/L for nebulized formulations 5

DRUG INTERACTIONS

Major Interactions (Avoid or Use with Extreme Caution)

Nephrotoxic Agents 5, 1:

• Loop diuretics (furosemide, ethacrynic acid) - increased ototoxicity risk
• Capreomycin - increased nephrotoxicity
• Cephalosporins - increased nephrotoxicity; may spuriously elevate creatinine
• Ciclosporin
• Colistimethate sodium
• Tacrolimus
• Vancomycin - particularly concerning combination 8

Other Aminoglycosides 5:

• No clinical benefit in combining amikacin with capreomycin, kanamycin, or streptomycin

Neuromuscular Blocking Agents 1:

• May cause postoperative respiratory muscle weakness

Beta-Lactam Antibiotics 1:

• In vitro inactivation when mixed with penicillins or cephalosporins
• Clinically significant only in severe renal impairment
• Administer by separate routes
• Specimens for assay should be handled promptly (frozen or treated with beta-lactamase)

Bisphosphonates 5:

• Increased risk of hypocalcemia

DOSING CONSIDERATIONS

Renal Impairment 2:

Critical principle: Reduce frequency, NOT dose, to maintain concentration-dependent bactericidal effect

• Dosing frequency: Reduce to 12-15 mg/kg per dose, 2-3 times weekly
• Maintain milligram dose at 12-15 mg/kg
• Hemodialysis patients: Give after dialysis to facilitate DOT and avoid premature drug removal
• Monitor serum drug concentrations to avoid toxicity

Hepatic Disease 2:

• No dose adjustment required
• However: Patients with severe hepatic disease at greater risk for hepato-renal syndrome; monitor renal function closely 2

Special Populations

• Elderly: Higher risk of nephrotoxicity and ototoxicity; creatinine clearance determination more useful than BUN/creatinine alone 1
• Pediatric MDR-TB: Associated with increased treatment success (aOR 2.94; 95% CI 1.05-8.28) 3

CLINICAL PEARLS

Key Practice Points:

1. Hydration is essential - patients should be well-hydrated to minimize renal tubular irritation 1
2. Single daily dosing preferred over divided doses due to concentration-dependent killing 3
3. Serum concentration measurements readily available (advantage over other aminoglycosides) 2
4. Stop treatment if: Progressive azotemia, decreased urinary output, or persistent renal irritation signs 1
5. For TB: Most streptomycin-resistant strains remain susceptible to amikacin 2