General Information

Infectious Diseases consultation recommended.

Body weight calculation (kg)

ABW = Actual body weight IBW = Ideal body weight

  • IBW (male) = 50.0 kg + [2.3 kg x (each inch greater 5 feet)]
  • IBW (female) = 45.5 kg + [2.3 kg x (each inch greater 5 feet)

DBW = dosing body weight

  • DBW = 0.4 x (ABW – IBW) + IBW

For “non-obese” patients use: ABW For “obese” patients use: DBW

  • Consider “obese” if (ABW - IBW) / IBW is greater than 0.2

Creatinine clearance (mL/min)

CrCl (male) = [(140 – age) x weight x 60] / [50 x serum creatinine (umol/L)]

CrCl (female) = CrCl (male) x 0.85

Age is in years.

Weight (kg) = ABW if non-obese, or = DBW if obese

Steady-State Plasma Concentration

  • The pharmacologic target for colistin is an average steady-state plasma concentration of 2 mg/L (Css,avg)

Susceptibility Breakpoint

  • The susceptibility breakpoint for colistin for Enterobacteriaceae, Pseudomonas aeruginosa, and Acinetobacter is less than or equal to 2 mg/L

Expressing Colistin Doses

  • Colistin doses in the scientific literature may be expressed in different ways. The conversion is as follows:
    • 1 million International Units of Colistin = 33 mg of Colistin Base Activity (CBA) = 80 mg of colistimethate (CMS)
  • All doses for Colistin should be expressed in Colistin Base Activity