COLY-MYCIN S
Clinical safety rating: caution
Comprehensive clinical and safety monograph for COLY-MYCIN S (COLY-MYCIN S).
Colistin is a polymyxin antibiotic that binds to lipopolysaccharides in the outer membrane of Gram-negative bacteria, disrupting the membrane and causing cell death.
| Metabolism | Colistin is primarily metabolized via hydrolysis to a lesser extent; hepatic CYP450 enzymes are not significantly involved in its metabolism. |
| Excretion | Renal: ~70-80% unchanged via glomerular filtration; biliary/fecal: ~15-20% as active drug and metabolites. |
| Half-life | Terminal elimination half-life: 2-4 hours in normal renal function; prolonged in renal impairment (up to 24-48 hours in anuria). |
| Protein binding | Colistin: ~50% bound to albumin; colistimethate sodium: <10% bound. |
| Volume of Distribution | Colistimethate: 0.3-0.6 L/kg; colistin: 0.5-1.0 L/kg (indicating distribution primarily into extracellular fluid). |
| Bioavailability | IM: ~60-70% of colistimethate is systemically absorbed; Oral: negligible (<1%); Topical: minimal systemic absorption (<0.1%). |
| Onset of Action | IM: 1-2 hours; IV: within 30-60 minutes; Topical: variable, within 24-48 hours for local effects. |
| Duration of Action | IM/IV: 6-8 hours with colistimethate; colistin base has longer duration (12-24 hours). Topical: depends on formulation, typically 12-24 hours. |
| Molecular Weight | 1155.4 |
2.5 mg/kg/dose IV every 12 hours for 7-14 days (based on colistin base activity).
| Dosage form | SUSPENSION |
| Renal impairment | CrCl 50-80 mL/min: 2.5 mg/kg IV every 24 hours; CrCl 30-49 mL/min: 2.5 mg/kg IV every 36 hours; CrCl 10-29 mL/min: 2.5 mg/kg IV every 48 hours; CrCl <10 mL/min: 2.5 mg/kg IV every 72 hours. |
| Liver impairment | No specific dose adjustment recommended; use with caution in severe hepatic impairment. |
| Pediatric use | Children ≥1 year: 2.5 mg/kg/dose IV every 12 hours based on colistin base activity; maximum 5 mg/kg/day. |
| Geriatric use | Dose based on renal function; monitor renal function closely due to age-related decline in CrCl. |
| 1st trimester | Avoid; colistin crosses placenta and has potential nephrotoxicity and ototoxicity risks; insufficient human data. |
| 2nd trimester | Avoid unless no safer alternative; use only if benefit outweighs potential fetal risks. |
| 3rd trimester | Avoid due to possible neonatal toxicity; consider alternative antibiotics. |
Clinical note
Comprehensive clinical and safety monograph for COLY-MYCIN S (COLY-MYCIN S).
| Placental transfer | Colistin crosses the placenta; studies show measurable concentrations in cord blood and amniotic fluid. |
| Breastfeeding | Colistin is excreted into breast milk in small amounts; limited data suggests low risk to infant; however, monitor for gastrointestinal disturbances or allergic reactions. |
| Lactation Rating |
■ FDA Black Box Warning
Nephrotoxicity and neurotoxicity: Colistin can cause acute kidney injury and neuromuscular blockade leading to respiratory arrest. Use with caution in patients with renal impairment and monitor renal function closely.
| Serious Effects |
Hypersensitivity to colistin or any componentPre-existing severe renal impairment (CrCl <10 mL/min) not on dialysis
| Precautions | Monitor renal function closely during therapy; dose adjustment required in renal impairment., Neurotoxicity may manifest as paresthesias, dizziness, slurred speech, vertigo, and neuromuscular blockade; use caution with concomitant neurotoxic agents., Clostridium difficile-associated diarrhea has been reported., Respiratory arrest has occurred, especially with rapid intravenous infusion or in patients with neuromuscular disorders. |
| Food/Dietary | No significant food interactions. May be taken with or without food. Maintain adequate hydration. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | FDA Pregnancy Category C. Colistimethate (active component) crosses placenta. First trimester: No adequate human data; teratogenic in animal studies (cleft palate, skeletal abnormalities). Second/third trimester: Potential for fetal nephrotoxicity and ototoxicity due to colistin accumulation; reserve for serious infections when no alternative. |
| Fetal Monitoring | Monitor maternal renal function (serum creatinine, BUN, urine output) and electrolyte levels (especially sodium and potassium). Assess for signs of nephrotoxicity or neurotoxicity (paresthesias, dizziness). In fetus, consider periodic ultrasound if prolonged therapy. |
| Fertility Effects | Animal studies show no impairment of fertility. No human data on fertility effects. |
| Clinical Pearls | Colistimethate sodium is a prodrug of colistin, a polymyxin antibiotic. It is reserved for multidrug-resistant Gram-negative infections. Nephrotoxicity and neurotoxicity are dose-limiting; monitor renal function closely. Inhalational use may cause bronchospasm; pretreat with bronchodilator. Dose adjustment required in renal impairment based on calculated CrCl. Avoid concurrent use with other nephrotoxic agents. Neuromuscular blockade possible; use caution with neuromuscular disease or concomitant neuromuscular blockers. |
| Patient Advice | Take this medication exactly as prescribed; do not skip doses. · If using the oral suspension, shake well before each use. · Report any signs of kidney problems: decreased urination, swelling, or fatigue. · Report numbness, tingling, or muscle weakness immediately. · If using the inhaled form, use a bronchodilator first if prescribed. · Drink plenty of fluids unless advised otherwise by your doctor. · Do not stop taking this medicine without consulting your doctor. |