About polymyxin bbasic polypeptide(polymyxin)antibiotic, antibiotic.mechanism of action of polymyxin bpolymixin b is a member of poly peptide antibiotic. being poly peptide they exert a detergent like effect. they have high affinity for phospholipids. peptide molecules orient between these phospholipids and cause cell membrane distortion and amino acids and ions come out with in the cell.polymixin b is useful against gram negative bacteria only.indications for polymyxin b1.skin infection 2.urinary tract infection 3.burns 4.enteric infection interactions for polymyxin baminoglycosides: concurrent use may increase risk of respiratory paralysis and renal dysfunction. non-depolarising muscle relaxants: neuromuscular blockade may be enhanced.