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Ira Leviton (talk | contribs) m Removed outdated html codes, changed FDA to United States Food and Drug Administration. |
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Because endotoxin molecular weight may vary a great deal (10,000 to 1,000,000 Da), endotoxin levels are measured in "endotoxin units" (EU). One EU is approximately equivalent to 100 pg of E. coli lipopolysaccharide—the amount present in around 10<sup>5</sup> bacteria. Humans can develop symptoms when exposed to as little as 5 EU/kg body weight. These symptoms include, but are not limited to, fever, low blood pressure, increased heart rate, and low urine output; and even small doses of endotoxin in the blood stream are often fatal.
The United States [[Food and Drug Administration
* Drug (injectable, [[intrathecal]]) - 0.2 EU/kg body weight
* Drug (injectable, non-intrathecal) - 5 EU/kg body weight
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;[[Ion exchange chromatography]]
:Endotoxins are negatively charged, and will bind to an ''[[anion exchanger]]''. If the target substance is not also negatively charged, it will pass through the column before the endotoxin, and an effective separation can be achieved. This method is sometimes used in the purification of [[albumins]] (details follow). [[Ligands]] of known affinity to endotoxins can be coupled to an anion exchange system to increase its endotoxin binding strength and further improve the purity of the final product. Typical examples of endotoxin binding ligands include [[histamine]], nitrogen-containing heterocyclic compounds, and [[polymyxin B]]. However, [[polymyxin B]] is known to induce production of interleukin-1, an exogenous pyrogen, and thus must be shown to be absent in the final product if used.
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:* 2% of the endotoxin ''does not'' bind to the column. However, this 2% washes out before the albumin peak, and can thus be removed simply by starting collection after this 2% has washed out.
:* 10% of the endotoxin that ''does'' bind to the column (9.8% of the original total) will eventually wash out after the albumin peak. This can be prevented from entering the final product by stopping collection before this happens.
:* The remaining 90% of the bound endotoxin (88.2% of the original total) must be cleaned off the column using NaOH
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;[[Ultrafiltration]]
:Because the molecular weight of endotoxins is usually over 10 kD, ultrafiltration can sometimes be used to perform as a size based separation. Due to the high variability of endotoxin size, it can be difficult to select the correct membrane, hence this method is best used only when all endotoxins present are larger than 300,000 Da. Commercially available ultra filters have been shown to remove pyrogens to a level below 0.001 EU/ml.{{citation needed|date=November 2010}}
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