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Amikacin Pharmacodynamics and Mechanism of Action

Introductin

Amikacin is a semi-synthetic aminoglycoside antibiotic derived from kanamycin A. Similar to other aminoglycosides, amikacin disrupts bacterial protein synthesis by binding to the 30S ribosome of susceptible organisms. Binding interferes with mRNA binding and tRNA acceptor sites leading to the production of non-functional or toxic peptides. Other mechanisms not fully understood may confer the bactericidal effects of amikacin. Amikacin is also nephrotoxic and ototoxic.

Indication
For short-term treatment of serious infections due to susceptible strains of Gram-negative bacteria, including Pseudomonas species, Escherichia coli, species of indole-positive and indole-negative Proteus, Providencia species, Klebsiella-Enterobacter-Serratia species, and Acinetobacter (Mima-Herellea) species. Amikacin may also be used to treat Mycobacterium avium and Mycobacterium tuberculosis infections.

Pharmacodynamics
Amikacin is an aminoglycoside antibiotic. Aminoglycosides work by binding to the bacterial 30S ribosomal subunit, causing misreading of t-RNA, leaving the bacterium unable to synthesize proteins vital to its growth. Aminoglycosides are useful primarily in infections involving aerobic, Gram-negative bacteria, such as Pseudomonas, Acinetobacter, and Enterobacter. In addition, some mycobacteria, including the bacteria that cause tuberculosis, are susceptible to aminoglycosides. Infections caused by Gram-positive bacteria can also be treated with aminoglycosides, but other types of antibiotics are more potent and less damaging to the host. In the past the aminoglycosides have been used in conjunction with penicillin-related antibiotics in streptococcal infections for their synergistic effects, particularly in endocarditis. Aminoglycosides are mostly ineffective against anaerobic bacteria, fungi and viruses.


MECHANISM OF ACTION


The aminoglycosides primarily act by binding to the aminoacyl site of 16S ribosomal RNA within the 30S ribosomal subunit, leading to misreading of the genetic code and inhibition of translocation . The initial steps required for peptide synthesis are uninterrupted, such as binding of mRNA and the association of the 50S ribosomal subunit, but elongation fails to occur due to disruption of the mechanisms for ensuring translational accuracy . The ensuing antimicrobial activity is usually bactericidal against susceptible aerobic gram-negative bacilli.

Amikacin Dosing Information

Usual Adult Dose for Bacteremia:

15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Intraabdominal Infection:

15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Joint Infection:
15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Osteomyelitis:

15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Pneumonia:

15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Skin or Soft Tissue Infection:

15 to 22.5 mg/kg/day IV or IM in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)

Usual Adult Dose for Cystic Fibrosis:

Higher doses may be required for the treatment of Pseudomonas aeruginosa pulmonary infections in cystic fibrosis patients. Dosing should be individualized and based on serum concentrations. Doses of up to 35 mg/kg/day once daily by IV infusion or in divided doses every 6 to 8 hours have been reported.

Usual Adult Dose for Febrile Neutropenia:

Higher doses may be required. Dosing should be individualized and based on serum concentrations. Doses of up to 15 to 30 mg/kg/day IV in 1 to 3 divided doses have been reported in conjunction with a beta-lactam antibiotic (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels).

Usual Adult Dose for Meningitis:

IV or IM: 15 to 22.5 mg/kg/day in 1 to 3 divided doses, depending on severity of infection (initial maximum of 1.5 g/day, then adjust dose based on desired serum levels)
Intrathecal: 0.1 mg per mL of CSF or approximately 2 mg/kg body weight per day has been used to treat gram-negative bacillary meningitis in conjunction with parenteral antibiotics

Usual Adult Dose for Nosocomial Pneumonia:

20 mg/kg /day IV in 1 to 3 divided doses

Initial empiric treatment with broad-spectrum coverage according to the hospital's and/or ICU's antibiogram is recommended if multidrug-resistant organisms are suspected.

Duration: If the causative organism is not Pseudomonas aeruginosa, the duration of treatment should be as short as clinically possible (e.g., as little as 7 days) to reduce the risk of superinfections with resistant organisms.

Usual Adult Dose for Peritonitis:

Peritoneal dialysis-related peritonitis:
CAPD intermittent dosing: 2 mg/kg in 1 exchange/day (based on ideal body weight) intraperitoneally for anuric patients and 2.5 mg/kg/bag for nonanuric patients (investigational)
CAPD continuous dosing: 24 mg/L exchange intraperitoneally for anuric patients and 30 mg/L for nonanuric patients

Maximum dose: 1.5 g/day by all routes

Usual Adult Dose for Tuberculosis -- Active:

15 mg/kg (maximum 1 g) IM or IV every 24 hours

May be given in combination with at least 3 other active drugs for treatment of multi-drug resistant TB, or when the patient is intolerant of first-line agents. AFB smear and culture should be monitored monthly.

Duration: Treatment for TB should generally continue for 18 to 24 months, or for 12 to 18 months after culture results are negative.

Usual Adult Dose for Urinary Tract Infection:

Uncomplicated: 250 mg IV or IM every 12 hours
Amikacin is not recommended for mild to moderate infections.

Usual Pediatric Dose for Febrile Neutropenia:

1 to 18 years: Higher doses may be required. Dosing should be individualized and based on serum concentrations. Doses ranging from 15 to 30 mg/kg/day in 1 to 3 divided doses have been reported in conjunction with a beta-lactam antibiotic.

Usual Pediatric Dose for Cystic Fibrosis:

1 to 18 years: Higher doses and/or more frequent intervals may be required. Dosing should be individualized and based on serum concentrations. Doses of up to 35 mg/kg/day IV in 1 to 3 divided doses have been reported.

Usual Pediatric Dose for Peritonitis:

Peritoneal dialysis-related peritonitis:
17 years or less:
Initial dose: 25 mg/L dialysate intraperitoneally
Maintenance dose: 12 mg/L dialysate

Maximum dose:
1.5 g/day by all routes

Usual Pediatric Dose for Tuberculosis -- Active:

15 to 30 mg/kg (maximum 1 g) IM or IV every 24 hours

May be given in combination with at least 3 other active drugs for treatment of multi-drug resistant TB, or when the patient is intolerant of first-line agents. AFB smear and culture should be monitored monthly.

Duration: Treatment for TB should generally continue for 18 to 24 months, or for 12 to 18 months after culture results are negative.
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Ditulis oleh: Unknown - Sunday 24 April 2011