Colistimethate: uses, dosing, side effects & brands

How colistimethate is dosed

From the FDA label for Coly-Mycin M (application NDA050108). Other colistimethate products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.

Important: Coly-Mycin M Parenteral is supplied in vials containing colistimethate sodium equivalent to 150 mg colistin base activity per vial. Reconstitution for Intravenous or Intramuscular Administration: The 150 mg vial should be reconstituted with 2 mL Sterile Water for Injection, USP. The reconstituted solution provides colistimethate sodium at a concentration equivalent to 75 mg/mL colistin base activity. During reconstitution swirl gently to avoid frothing. Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. If these conditions are observed, the product should not be used. Dosage Adults and Pediatric Patients—Intravenous or Intramuscular Administration: The dose of Coly-Mycin M Parenteral should be 2.5 to 5 mg/kg per day of colistin base in 2 to 4 divided doses for patients with normal renal function, depending on the severity of the infection. In obese individuals, dosage should be based on ideal body weight. The daily dose and frequency should be reduced for the patients with renal impairment. Suggested modifications of dosage schedule for patients with renal impairment are presented in Table 1. TABLE 1. Suggested Modification of Dosage Schedules of Coly-Mycin M Parenteral for Adults with Impaired Renal Function Degree of Renal Impairment Normal Mild Moderate…

Colistimethate side effects

Who shouldn’t take colistimethate

Colistimethate drug interactions

How long colistimethate keeps

The date on a sealed pack is not the only one: some colistimethate labels start a second clock once the product is opened or mixed, as short as 7 days.

Colistimethate and breastfeeding

From LactMed, the US National Library of Medicine’s Drugs and Lactation Database — quoted, not rewritten.

Limited data indicate that colistin is minimally excreted into breastmilk following intramuscular administration of colistimethate. Because colistin is poorly absorbed orally, it is unlikely to be absorbed in appreciable amounts by the infant or adversely affect the breastfed infant. However, no studies have evaluated serum levels or adverse effects in breastfed infants whose mothers were receiving colistimethate. Breastfeeding is acceptable with the use of inhaled colistin or colistimethate.

National Institute of Child Health and Human Development, record revised November 15, 2024. LactMed states its information is not a substitute for professional judgement.

What people report to the FDA about colistimethate

The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 1,271 reports naming colistimethate, and the FDA flagged 92% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:

• hospitalisation121 reports
• acute kidney injury79 reports
• septic shock53 reports
• thrombocytopenia48 reports
• dyspnoea47 reports
• cystic fibrosis46 reports
• infective pulmonary exacerbation of cystic fibrosis46 reports
• pneumonia41 reports

Source: openFDA drug/event (FAERS), retrieved July 25, 2026.

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