Depyrogenation is the removal of pyrogen (endotoxins) from the pharmaceutical materials or equipments. Endotoxins are the lipopolysaccharides found in the cell walls of the gram negative bacteria. Pyrogen causes fever when enter in bloodstream.
Endotoxin is measured in Endotoxin Units (EU). Endotoxin in water for injection (WFI) should not be more than 0.25 EU/ml. There are following methods for depyrogenation in pharmaceuticals.
1. In Quality Control: All instruments used in analysis for endotoxin should be depyrogenated to get accurate results. Test tubes and other accessories are depyrogenated by heating in dry heat sterilizer (DHS) at 300ºC.
2. In Manufacturing: In sterile product manufacturing vials are depyrogenated by dry heat at 300ºC using depyrogenating tunnel. A combination of temperature of chamber and belt speed is used to get effective depyrogenation of the glass vials.
Bungs, change parts and other accessories are washed with water for injection (WFI) and then sterilized in autoclave. Rinse water of bungs and change parts is analyzed for bacterial endotoxin to prove the removal of pyrogen.
3. Water: Water used in sterile manufacturing should be free from the pyrogens. Purified water is heated and distilled to produce the water for injection (WFI). As endotoxins are heat sensitive, they are denatured during the distillation process and these have higher molecular weight than water. Due to heavy molecular weight these are not distilled with water and remains in distillation tank.
Method used for depyrogenation of equipments and accessories should be validated. Standard endotoxin is used to validate the process. Minimum 3 log reduction of endotoxin is accepted.
There are many methods to detect the endotoxin but gel clot method is most popular and widely used method.
Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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