Antibilharzial agents

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Antibilharzial agents

• Dr\ Moustafa K Soltan

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I Antimonial drugs Antimony potassium
tartarate, Stipophen, Sodium stipocaptate. (contai
ning trivalent antimony). II Non antimonial
drugs classified chemically into the following
classes Quinoline derivatives Oxamniquine,
Praziquantil (broad spectrum anthelmintic). Thiox
anthenone derivatives Lucanthone,
Hycanthone. Organic phosphates
Metrifonate. Nitro heterocyclic derivatives
Niridazole.
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Antimonial drugs.
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Antimony pot tartarate Uses Used formerly for
treatment of S. Japonicum Stibophen Alternative
drug for S. Mansoni Sod stibocaptate
Effective against the 3 forms of
schistosoma.(japonicum, mansoni, haematopium)
Mechanism of action antimonial drugs inhibit
phosphofructokinase enzyme that is involved in
glycolysis what lead to their death.(by covalent
binding with SH gp) Host phosphofructokinase is
less sensitive 80 times to these drugs than that
of schistosoma and so these drugs exhibit
selective toxicity.
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Generally all antimonial compounds are not used
now due to their toxicity and main side
effects. The trivalent are generally more toxic
than pentavalent ones as former are poorly
absorbed from the GIT and also less excreted.
Non antimonial drugs 1)quinoline derivatives
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Oxamniquine. Uses Used for treatment of S.
Mansoni. Mechanism of action It inhibit DNA,
RNA and protein synthesis Oxamniquine is
biotransformed into inactive 6-carboxymethyl and
so 6-hydroxymethyl group is important for
activity. Praziquantel. Uses Broad spectrum
anthelmintic drug used in 1) All types of
schistosoma. 2) Treatment of intestinal and liver
flukes. 3) Treatment of taeniasis and no
purgative is needed after its administration.
Mechanism of action The drug increases the
permeability of the worm cell membrane to the
Ca ions what causes massive contractions and
paralysis of the fluke musculature, followed by
phagocytosis of the parasite.
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2) thioxanthenone derivatives
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Hycanthone Lucanthone. Uses Treatment of S.
Haematobium., S. Mansoni But now, they are seldom
used as they have mutagenic and carcinogenic
activity. Hycanthone is the metabolic product
of lucanthone and it is less toxic and more
active than lucanthone.
3)organic phosphate drugs
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Metrifonate. UsesAlternative drug for treatment
of S. Haematobium. It is not used now due to
its severe side effects, praziquantel is used
instead of it, cause side effects that are due
to parasympathetic system stimulation, diarrhea,
abdominal pain, headache, vertigo, vomiting,
others. Mechanism of action It is an acetyl
choline esterase inhibitor, causes persistant
depolarization of the musculature of parasite,
causing paralysis followed by phagocytosis.
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4) nitroheterocyclic drugs.
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Niridazole. Uses Treatment of S.
Haematobium.. moderately for treatment of S.
Mansoni. Intestinal amoebiasis. Side effects
are severe mental disorientation, mania,
convulsions. Mutagenic, carcinogenic. Serious
effect on heart.