colistin sulfate + tobramycin + amphotericin B

A non-absorbable oral suspension combining three antibiotics—colistin sulfate, tobramycin, and amphotericin B—is used primarily for selective decontamination of the digestive tract (SDD) in intensive care patients. This combination aims to reduce the risk of pneumonia and bacteremia in intubated patients by suppressing pathogenic bacteria and fungi in the gut. Colistin is a polymyxin antibiotic that disrupts Gram-negative bacterial cell membranes; tobramycin is an aminoglycoside antibiotic that inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit; amphotericin B is a polyene antifungal that binds irreversibly to ergosterol in fungal cell membranes, causing increased permeability and cell death[1][2][3][4]. The formulation is not standardized across all pharmacies but typically includes these three agents suspended in an aqueous solution with preservatives for oral administration.