Polymyxin B sulphate

The antibacterial activity of five members (A to E) of the polymyxin group is of a similar nature. However, they are all nephrotoxic although this effect is much reduced with polymyxins B and E (colistin). Colistin sulphomethate sodium is the form of colistin used for parenteral administration. Sulphomyxin sodium, a mixture of sulphomethylated polymyxin B and sodium bisulphite, has the action and uses of polymyxin B sulphate, but is less toxic. 

Bacitracin, polymyxin B sulphate, neomycin, gentamicin, gramicidin, mupirocin (T-BACT)... 

Other evidence shows that histamine is not the main mediator in the anaphylactoid reaction. For example, the injection of histamine itself does not elicit all the symptoms which are typical of an anaphylactoid response [171]. Moreover, egg-white and dextran elicit a full anaphylactoid oedema in rats whose skin histamine has been reduced to about 9% of the control values by compound 48/80 pretreatment [371]. Depletion studies with the antibiotic polymyxin B sulphate indicate that a maximum release of skin histamine, with little change of the tissue 5-hydroxytryptamine, does not modify the egg-white or dextran reactions [485]. Not all antihistamines inhibit the anaphylactoid reaction [90, 187, 248, 463, 464, 487, 530], and it is possible that the antihistamines found by earlier workers to inhibit the reaction possessed non-specific effects and especially anti-5-hydroxytryptamine activity [61,137, 203, 489]. 

HT is relatively more potent than histamine in increasing vascular permeability in the rat [61, 137, 414, 485, 487, 534, 578, 581]. Parratt and West [482-490] extensively studied the significance of the presence of the substantial amounts of both 5-HT and histamine in the skin and subcutaneous tissues of the rat, and the importance of their release from these sites during the anaphylactoid reaction. Polymyxin B sulphate released more than 90% of the histamine in the rat skin but less than 20% of its 5-HT on the other hand, reserpine released more than 90% of the 5-HT but only small amounts of the histamine. Pretreatment with reserpine, but not with polymyxin B sulphate, effectively inhibited both the egg-white and dextran anaphylactoid reaction. Further evidence for an important role of 5-HT in the anaphylactoid reaction was obtained when it was found that after an intraperitoneal injection of egg-white or dextran 5-HT, but not histamine, was present in the oedema fluid associated with the subcutaneous tissues on the dorsal side of the foot. 

The therapeutic effectiveness of the polymyxins " and colistin has been determined against a variety of experimental g am-negative infections, particularly in mice. In general the in vivo results parallel those in vitro. Both are effective when administered subcutaneously, intraperitoneally or intravenously, but are either inactive or only slightly active when given orally . Significant differences in the relative effectiveness of colistin sulphate, colistin methane sulphate and polymyxin B sulphate against K. pneumoniae and E. coli infections in mice have been demonstrated . 

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