Colistimethate (Coly-Mycin M) — Compare Prices at US & Canada Pharmacies

Colistimethate is an injectable polymyxin antibiotic reserved for serious infections caused by multidrug-resistant gram-negative bacteria, particularly Pseudomonas aeruginosa, when other antibiotics aren't a safe or effective option. It converts in the body to colistin, an older antibiotic that fell out of routine use decades ago because of its toxicity, but has seen renewed use as resistant infections have become more common and treatment options have narrowed.

Colistimethate's two best-known risks are nephrotoxicity (kidney damage, which is largely dose-dependent) and neurotoxicity — the FDA label describes transient neurological effects like facial numbness or tingling, dizziness, vertigo, and slurred speech that can occur during treatment. Because of this, people receiving it are warned not to drive or operate machinery, and kidney function is monitored closely throughout treatment, with the dose adjusted accordingly.

The WHO AWaRe framework classifies colistimethate as a Reserve antibiotic — the category for last-line drugs meant to be used carefully, specifically for confirmed or strongly suspected resistant infections, both to protect patients from its narrower safety margin and to help preserve its usefulness against bacteria that few other drugs can still treat.

Contraindications

CONTRAINDICATIONS The use of Colistimethate for Injection, USP is contraindicated for patients with a history of sensitivity to the drug or any of its components.

Warnings

WARNINGS Maximum daily dose calculated from colistin base activity should not exceed 5 mg/kg/day with normal renal function. Transient neurological disturbances may occur. These include circumoral paresthesia or numbness, tingling or formication of the extremities, generalized pruritus, vertigo, dizziness, and slurring of speech. For these reasons, patients should be warned not to drive vehicles or use hazardous machinery while on therapy. Reduction of dosage may alleviate symptoms. Therapy need not be discontinued, but such patients should be observed with particular care. Nephrotoxicity can occur and is probably a dosedependent effect of colistimethate sodium.

Pregnancy & breastfeeding

Pregnancy Teratogenic Effects Pregnancy Category C Colistimethate sodium given intramuscularly during organogenesis to rabbits at 4.15 and 9.3 mg/kg resulted in talipes varus in 2.6% and 2.9% of fetuses, respectively. These doses are 0.25 and 0.55 times the maximum daily human dose based on mg/m 2 . In addition, increased resorption occurred at 9.3 mg/kg. Colistimethate sodium was not teratogenic in rats at 4.15 or 9.3 mg/kg.