Colistimethate
Synonyms :
Colistin, Colistin Sulphate, Polymyxin E
Mechanism :
Colistimethate is a surface-active agent which penetrates into and disrupts the bacterial cell membrane. Colistimethate is polycationic and has both hydrophobic and lipophilic moieties. It interacts with the bacterial cytoplasmic membrane, changing its permeability. This effect is bactericidal. There is also evidence that polymyxins enter the cell and precipitate cytoplasmic components, primarily ribosomes.
Indication :
- MDR gram negative infection
- Pseudomonas lung infection in cystic fibrosis
Contraindications :
Hypersensitivity
Dosing :
Pseudomonas lung infection in cystic fibrosis:
Nebulised along with oral ciprofloxacin.
<1 year: 500,000 units 2 times daily.
1-10 year: 1 million units 2 times daily.
>10 years: 2 million units 2 times daily.
MDR gram negative infections: 2.5-5 mg/kg/day in 2-4 divided doses IV/IM.
Adverse Effect :
Dizziness, paresthesia, tingling sensation, neurotoxicity, nephrotoxicity, acute respiratory failure (inhalation route), respiratory tract paralysis.
Interaction :
Atracurium: Increases the effects of colistimethate.
Bacitracin: May increase nephrotoxicity or ototoxicity.
Skeletal Muscle Relaxants: Increases effects of colistimethate by pharmacodynamic synergism.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 20-50 | IV: 1–2 million units every 8 hours. Oral: Dose as in normal renal function; use with caution |
| 10-20 | IV: 1 million units every 12– 18 hours or 50% of dose. Oral: Dose as in normal renal function; use with caution |
| <10 | IV: 1 million units every 18– 24 hours or 30% of dose. Oral: Dose as in normal renal function; use with caution |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Dialysed. Dose as in GFR<10 mL/ min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Dialysed. Dose as in GFR<10 mL/ min |
| CAV/VVHD | Not dialysed. 2 million units every 48 hours |
Hepatic Dose :
No dosage adjustments are recommended.