Colistimethate (Colistin) Intravenous for Adult patients

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Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

  • Restricted antibiotic (unless for Cystic Fibrosis): The intravenous route is reserved for serious infections with limited treatment options, following approval by microbiology/infectious diseases/CF consultant. Should be used only as part of combination therapy.
  • The dosing regimen depends on the indication.
    • Conventional dose - for cystic fibrosis patients (as per Leeds guideline) (ref 1)
    • High Dose Regimen (as per SPC)
    • The dose in renal impairment differs for the two regimens
  • Commonly used in cystic fibrosis patients by inhalation via a nebuliser - see under 'Further information'
  • Nephrotoxic and neurotoxic. Risk factors include IV route, high doses, cumulative dose, and other nephrotoxins (ref 2)
  • See monitoring requirements
  • See under 'Dose' for adjustments required in renal impairment

Available preparations

Colomycin 1 million units vial

Colomycin 2 million units vial

Reconstitution

Sodium Chloride 0.9% or Water for Injection

Usually: 10ml per vial

Infusion fluids

Sodium chloride 0.9%

Methods of intravenous administration

Intravenous infusion (preferred method)

  • Dilute to 100ml with infusion fluid and administer over 30 to 60 minutes (ref 3)
  • The residual volume in the infusion line must be flushed through at the same rate to avoid significant underdosing
  • For the 9 Million unit dose: Reconstitute each 1 million unit vial with 5ml. Remove 50ml infusion fluid from a 100ml bag and add 45ml (9 million units) of drug solution to produce a final volume of 95ml

Slow intravenous injection (Patient must have Totally Implantable Venous Access Device)

  • This route is only for doses of up to 2 million units (in 10ml)
  • Administer required dose over at least 5 minutes

Dose in adults

Conventional dosing regimen (cystic fibrosis) (ref 1)

  • Patients greater than 40kg: 2 million units every eight hours
  • Patients less than 40kg: give 1 million units every eight hours

NON-Cystic Fibrosis HIGH DOSE REGIMEN

  • Restricted antibiotic: see Important Information
  • Loading dose of 9 million units, followed twelve hours later by 4.5 million units every twelve hours
  • The loading dose applies to patients with both normal and impaired renal function, including those on renal replacement therapy

Renal impairment

Cystic fibrosis:

  • Dosage in Cystic Fibrosis patients with renal impairment is individualised (Consultant and CF Pharmacist input required)

Non- Cystic Fibrosis patients - see table below

Renal impairment - NON-CYSTIC FIBROSIS - High Dose Regimen
Creatinine clearance (ml/min)- calculate using Cockcroft and Gault equation Dose Frequency
30 to 49 Give 9 million units loading dose, followed 12 hours later by 2.75 to 3.75 million units every twelve hours
10 to 29 Give 9 million units loading dose, followed 12 hours later by 2.25 to 2.75 million units every twelve hours
less than 10 Give 9 million units loading dose, followed 12 hours later by 1.75 million units every twelve hours
Renal replacement therapy Consult pharmacy or see specialist texts

Monitoring

  • Monitor carefully for parasthesias, which may indicate neurotoxicity as a sign of overdose
  • Monitor renal function carefully at the start of, and regularly during treatment
  • The BNF recommends the monitoring of levels, especially in renal impairment
  • Levels are not routinely available- if required consult microbiology

Further information

  • Confusion and medication errors have occurred because of the different expression of dose in the EU (units) and the US (mg) markets
  • 1 million units of Colistin is approximately equal to 80mg Colistin
  • i.e. 1mg of Colistin is approximately equal to 12,500units of Colistin (However Colistin is normally prescribed in units)

Nebulised colistin

Required equipment (available from stores) (ref 4)

  • Nebuliser compressor
  • Jet nebuliser e.g PARI PL PLUS (022G8000) or PARI LC SPRINT (023G6001)
  • PARI tubing (041B4592)
  • PARI filter set (041G0500)
  • Use mouthpiece rather than a mask
  • The filters should be changed after each use of the nebuliser

Dose and preparation

  • Dose by inhalation (adults and children>2 years): 1 to 2 Million units every 8 to 12 hours
  • Reconstitute each vial (1 or 2MU) with 4ml of sodium chloride 0.9% (preferred), or Water for Injection and give via nebuliser (ref 4)

Contact details

  • Contact the respiratory nurse for additional information on equipment

    Storage

    • Store below 250C

    References

    SPC Colomycin June 2023

    1: Leeds Centre for Cystic Fibrosis December 2023 - advised by Dr O Mahony that this is our preferred reference for adult doses of colomycin in cystic fibrosis patients

    2: Renal drug database accessed online 20/04/2026

    3: Injectable drugs guide- Medusa, accessed online 20/04/2026

    4. Galway University Hospitals Inhaled Antibiotic Guidelines in Adults Version 2.0, Nov 2024

    Therapeutic classification

    Polymixin antibiotic

    IV Guide Type
    Antimicrobial