1. Guided by Prepared By
Mrs.Tanvi pandya PARTH PATEL
M.Pharm Sem-1
Quality Assurance

2.  Sources of Pyrogens
 Pyrogen definition
 Classification of Pyrogens
 Properties of Endotoxins
 Chemical Nature of Endotoxin
 Biological properties of endotoxin
 Physical properties of endotoxins
 Mechanism of pyrogens
 References

3. PYROGENS DEFINITION:
 Pyrogens are fever producing substances,
which are metabolic products of
microorganisms.
 Chemically, they are lipid substances
associated with a carrier molecule, which is
usually a polysaccharide. The carrier may
also be a peptide. These carriers increase
the solubility of the lipid.
 Pyrogens are produced by many
microorganisms including bacteria, yeasts
and moulds. Most potent pyrogens are the
endotoxins produced from the cell walls of
the Gram- negative bacteria.

4. Sources of Pyrogens:
 Solvents, drugs, additives apparatus used in
manufacture, containers; all or any of these
may be sources of pyrogens.
 The method of storage in between
preparation and sterilization also may cause
the development of pyrogens.
 Hence every item must be apyrogenic and
method of storage must not allow any
bacterial growth.

5. Classification of Pyrogens
The scientific literature divides Pyrogen in two
broad classes.
 Exogenous Pyrogen ( Exotoxins)
 Endogenous Pyrogen (Endotoxin)

6. Exogenous Pyrogen ( Exotoxins)
Non microbial Pyrogens Microbial Pyrogens
Non host host origin
origin
Bacteria (killed or live), Fungi
Non microbial exogenous Non microbial exogenous (killed or live), plasmodia
pyrogens of nonhost pyrogens of host origin include (malarial parasites),and
origin include Antigen-Antibody complexes, viruses(live) can all act as
pharmacologic agent like products of lymphocytes and pyrogens, additionally bacterial
bleomycin, colchicin and metabolic Products of products, including streptococcal
polynucleotide poly- 1: C, androgenic steroids endotoxin, staphylococcal
endotoxins.
Microbial exogenous pyrogens
Most of non microbial pyrogen
are much more of a problem for
forms produce fever by inducing
pharmaceutical manufacturers;
the synthesis and release of
the lipopolysaccharide in the
endogenous pyrogen from host
endotoxin is toxic in small
phagocytic cells.
Quantities. 6

7. Endogenous Pyrogens
Exogenous pyrogen don't act directly on the thermoregulatory center of
the hypothalamus of the brain to cause fever,
Instead exogenous pyrogens stimulates the production of intermediate
heat-labile, Protienacious, mediator substances,Since this mediator
substance was first isolated from granulocytes,
It was initially called granulocytic pyrogen or sometimes leukocytic
pyrogen,After the mediator substance was found in the circulatory serum
of febrile rabbits it was called endogenous pyrogen
Endogenous pyrogen are produced by blood monocytes, Eiosinophils,alveolar
macrophages and fixed- tissue macrophages such as splenic sinusoidal cells and
hepatic kupffer cells,
When injected in to animals, It also induced hepatic acute-phase protein
synthesis,caused decrease in plasma iron and zinc levels produced neutrophilia,
stimulated serum amyloid, a protein synthesis and augmented T cells response to
mitogen and antigens.
7

8.  The biological activity of endotoxin is
associated with the lipopolysaccharide (LPS).
Toxicity is associated with the lipid
component (Lipid A) and immunogenicity is
associated with the polysaccharide
components. The cell wall antigens (O
antigens) of Gram-negative bacteria are
components of LPS. LPS elicits a variety of
inflammatory responses in an animal and it
activates complement by the alternative
(properdin) pathway, so it may be a part of
the pathology of Gram-negative bacterial
infections.

9.  Endotoxin has a polysaccharide structure that is
covalently bound to a lipid component, called lipid A
The polysaccharide component is composed of two
distinct parts, the core oligosaccharide that is connected
to lipid A and a longer oligosaccharide O-specific chain
that is attached to the core and is the outer most part of
the LPS Complex.
The O-specific chain is the most variable component of
the complex.
9

10.  It consist of 20-40 repeating units that include up to
the eight sugars, and it is responsible for the specific
immune reaction that each type of gram- negative
bacteria is able to evoke in a host ,
 The core oligosaccharide is much less variable than
O-specific chain and its influence on the host is less
profound,

12. The lipid A is the least variable components of LPS. It consists of a
disaccharides of glucosamine which is the highly substituted with amide-
linked and structure-linked long chain fatty acids,
Lipid A is the most interesting portion of LPS because it is responsible for
the vast majority of the harmful and the beneficial biological activities that
have been attributed to endotoxins .

13. BIOLOGICAL PROPERTIES OF ENDOTOXINS:
 Endotoxins are potent substances which elicit
a broad spectrum of the harmful physiologic
responses, Profound alteration in organ
function, such as hypotension and
disseminated intravascular coagulation, which
can lead to severe morbidity or death
 But on the other hand endotoxins are also
active stimulators of the mammalian defense
system,
 This capacity can enhance the body’s capacity
to cope with both microbial infections and
malignant tumors.


14. Physical properties of endotoxins
 It is important to be aware of the various
physical properties of endotoxin in order to
understand why they change their behavior
when placed into different environments,
 An understanding of these physical
properties is also essentials for designing
effective process for depyrogenation.
 Heat stability
 Size
 Molecular weight
 Electrostatic properties

15. Mechanism of pyrogens
 A trigger of the fever, by pyrogen, causes a
release of prostaglandin E2 (PGE2). PGE2 then in
turn acts on the hypo Temperature is ultimately
regulated in the hypothalamusthalamus, which
generates a systemic response back to the reset
of the body, causing heat-creating effects to
match a new temperature level
 A pyrogen is a substance that induces fever.
These can be either internal (endogenous) or
external (exogenous) to the body.
 The bacterial substance lipopolysaccharide (LPS),
present in the cell wall of some bacteria, is an
example of an exogenous pyrogen.

16.  Cytokines (especially interleukin 1) are a part of
the innate immune system, are produced by
phagocytic cells, and cause the increase in the
thermoregulatory set-point in the hypothalamus.
Other examples of endogenous pyrogens are
interleukin 6 (IL-6), and tumor necrosis factor-
alpha.
 Fever signals sent to the DMH and rRPa lead to
stimulation of the sympathetic output system,
which evokes non-shivering thermogenesis to
produce body heat and skin vasoconstriction to
decrease heat loss from the body surface.
 It is presumed that the innervation from the POA
to the PVN mediates the neuroendocrine effects
of fever through the pathway involving pituitary
gland and various endocrine organs

18. References
 Encyclopedia of Pharmaceutical Technology,
Volume:13,By James Swarbick & James Boylan.
 Indian Pharmacopoeia 2007,Vol.-1,Appendice-,
 British Pharmacopoeia 2007,
 United state pharmacopoeia
 Remington( The science and practice of
pharmacy), Volume-I , Page no.562,832.
 The text book of pharmaceutical Technology, By
Leon Lachman,
 Kenneth Todar online textbook of Bacteriology