Does colistimethate expire?
The printed date covers the sealed pack. Once colistimethate is opened, mixed or diluted, its label sets a second and usually much shorter limit — quoted below, per product.
Shortest limit on any colistimethate label: 7 days
“Store reconstituted solution in refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F), and use within 7 days.”
That applies to the product it is printed on, not to every form of colistimethate — check which one you have against the list below.
What the labels say
“Store reconstituted solution in refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F), and use within 7 days.”
On the label for Colistimethate · DailyMed
“Store reconstituted solution for intramuscular injection in a refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F), and use within 7 days.”
On the label for Colistimethate · DailyMed
“Store reconstituted solution in refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F) and use within 7 days.”
On the label for COLISTIMETHATE SODIUM · DailyMed
“Store reconstituted solution for intramuscular injection in a refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F) and use within 7 days.”
On the label for COLISTIMETHATE SODIUM · DailyMed
“Store reconstituted solution in refrigerator 2º to 8ºC (36º to 46ºF) or between 20º to 25ºC (68º to 77ºF) and use within 7 days.”
On the label for Colistimethate · DailyMed
How the label says to keep colistimethate
Storage is the other half of the question: the stability behind any date assumes these conditions, and a medicine kept outside them ages faster than the calendar says.
- “Store between 20° to 25°C (68° to 77°F).”
- “Store reconstituted solution in refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F), and use within 7 days.”
- “Store reconstituted solution for intramuscular injection in a refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F), and use within 7 days.”
- “Store unreconstituted product at 20° to 25°C (68° to 77°F); excursions permitted between 15° to 30°C (59° to 86°F) [see USP Controlled Room Temperature].”
- “Store reconstituted solution in refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F) and use within 7 days.”
- “Store reconstituted solution for intramuscular injection in a refrigerator 2° to 8°C (36° to 46°F) or between 20° to 25°C (68° to 77°F) and use within 7 days.”
- “Store unreconstituted product between 20° to 25°C (68° to 77°F).”
- “Store unreconstituted product between 20º to 25ºC (68º to 77ºF) (see USP Controlled Room Temperature).”
Frequently asked questions
Does colistimethate expire?
Two different clocks apply and only one of them is the printed date. The date on a sealed pack is the manufacturer's guarantee for the unopened product. Once it is opened, mixed or diluted, the label imposes its own limit — as tight as 7 days on some colistimethate products, and that is the number quoted on this page.
Can I still use colistimethate after the date on the box?
This page cannot tell you that, and nor can any page. The FDA's own shelf-life programme found 88% of tested lots stayed within specification at least a year past expiry — and concluded in the same breath that lot-to-lot variation means this can only be confirmed by testing each lot. What you can check at home is the in-use limit above and whether the product has been stored as the label requires. Ask a pharmacist about a specific pack; they will also dispose of what you no longer need.
Why do different colistimethate products have different limits?
Because they are different formulations. A suspension that gets mixed with water, a pen that gets carried at room temperature, and a sealed tablet do not behave alike, so each manufacturer's label sets its own limit and each is shown here with the product it belongs to. We never merge them into one number for the molecule.
More on colistimethate
Quoted from FDA labels for reference, not medical advice, and not a suggestion to use anything past its limit. If you are unsure whether a pack is still good, a pharmacist can tell you and can dispose of it safely.