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Anthelmintics SCHISTOSOMIASIS

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Title: Anthelmintics SCHISTOSOMIASIS


1
Anthelmintics SCHISTOSOMIASIS
Alia Alshanawani Pharmacology Dep, Medical
College KSU.
2
  • TREMATODES
  • also called as flukes
  • are leaf shaped flat worms
  • characterized by ! tissues they infect as
    parasite
  • Lung / Liver / Intestinal / Blood FLUKES.

3

Schistosomiasis Also known as
bilharzia, bilharziosis / snail fever is a
parasitic disease caused by several species of
fluke of ! Genus Shistosomiasis. Caused by
trematodes 1. Schistosoma haematobium 2. S.
mansoni 3. S. japonicum.
4
  • Although it has a low mortality rate,
    schistosomiasis often is a chronic illness that
    can damage internal organs , in children, impair
    growth cognitive development.
  • The urinary form of schistosomiasis is
    associated with increased risks for bladder
    cancer in adults.
  • Schistosomiasis is the 2nd most
    socioeconomically devastating parasitic disease
    after malaria.

5
LIFE CYCLE
6
  • Schistosomiasis (New world)
  • S. mansoni S. Japonicum
  • Primary site of infection is GIT.
  • Damage to intestinal wall is caused by hosts
    inflammatory response to eggs deposited at that
    site.
  • The eggs also secrete proteolytic enzymes that
    further damage ! tissue.
  • Diagnosis eggs in stools.
  • GIT bleeding, diarrhea, Liver damage.

7
  • Schistosomiasis (old world)
  • S. Haematobium
  • ! primary sites of infection veins of urinary
    bladder
  • eggs induce fibrosis , granulomas haematuria.
  • transmitted by direct skin penetration.
  • Diagnosis eggs in ! urine / bladder wall.

8

Antischistosomal drugs
  • Praziquantel (all schistosomal diseases)
  • 2. Metrifonate (S. haematobium)
  • 3. Oxamniquine (S. mansoni).

9
  • Praziquantel
  • a synthetic isoquinoline pyrazine derivative
  • PK
  • rapid po absorption
  • maximum plasma conc 1-3 hr.
  • Cross BBB.
  • bound to plasma proteins (80).
  • undergoes 1st pass metabolism to inactive
    metabolite.

10
  • T1/2 0.8 - 3 hr (increases in liver disease).
  • excreted in urine bile.
  • Bioavailability
  • Increased by carbohydrate meal cimetidine.
  • Reduced by antiepileptics (phenytoin
    carbamazepine).

11
  • Mechanism of Action of praziquantel
  • increases trematode cell membrane permeability to
    Ca2 contraction, paralysis, dislodgement
    death.

12
  • Anthelminthic action praziquantel
  • broad spectrum anthelminthic drug
  • effective in the Tr of schistosome infections of
    all species most other trematodes cestodes
    (tapeworms) but
  • nematodes (round worms) are unaffected.
  • effective against mature immature stages of
    worms.
  • Cure rate is up to 95.

13
  • Clinical uses praziquantel
  • Schistosomiasis
  • Drug of choice for all forms
  • For S.Japonicum infections, 20 mg/kg at
    intervals 4-6 hours for a total of 3 doses.
  • For S.mansoni and S.hamatobium 40 mg /kg in two
    divided doses.

14
  • taken after meals.
  • the interval between doses should not be lt than
    4 hr not gt than 6 hr.
  • effective in children adults.

15
  • 2- Other trematodes infections
  • Clonorchiasis (liver), paragonimiasis (lung)
  • 3- Cestodes infections
  • Taeniasis diphyllobothriasis (intestine)
  • Neurocysticercosis (albendazole is preferred)
  • Hymenolepis nana
  • Hydatid disease.

16
  • Adverse reactions of praziquantel
  • Headache, dizziness, drowsiness.
  • GIT disturbances.
  • Pruritus, urticaria, arthralgia, myalgia.
  • transient elevation of liver enz.
  • Fever, skin rashes , augmented eosinophilia may
    appear after several days release of foreign
    protein from dying worm.

17
Adverse reactions of praziquantel
  • In neurocysticercosis neurologic abnormalities
    (headache, mental changes, seizures) increases by
    inflammation around dying parasite.
  • Rx
  • used with corticosteroids.

18
Contraindication precautions
  • Ocular cysticercosis for fear of destruction of
    parasite in eye.
  • Children lt 4 years.
  • Pregnancy nursing mothers.
  • Driving.
  • Activities require alertness physical
    coordination (prohibited).
  • Reduce the dose in liver impairment.
  • Patient should be informed not chewing bitter
    taste

19
Metrifonate (TRICHLORFON)
  • Organo-phosphate compound
  • PK
  • Rapid po absorption.
  • t1/2 1.5 hr.
  • Nonenzymatic transformed to active metabolite.
  • widely distributed to tissues.
  • Excreted in urine.

20
Pharmacodynamics Metrifonate
  • produces its effect due to inhibition of
    cholinesterase, produces depolarizing block of S.
    haematobium
  • paralyzes the adult worm their shift from
    bladder venous plexus to a small arterioles of
    the lungs, where they are trapped by ! immune
    system killed.
  • NOT effective against S. haematobium eggs, only
    adult worms are killed.

21
Clinical uses Metrifonate
  • Safe, low cost alternative drug for S. hematobium
    infections ONLY .
  • A single dose of 7.5-10 mg /kg 3 times at 14 days
    intervals.
  • effective as prophylactic when given monthly to
    children in a highly endemic area.
  • In mixed infection with S. haematobium S.
    mansoni metrifonate oxamniquine.

22
  • Adverse reactions of Metrifonate
  • Mild cholinergic symptoms
  • N , V, diarrhea, abdominal pain,
  • B.spasm, headache, sweating, fatigue, weakness,
    dizziness,
  • vertigo
  • these start after 30 min persist up to 12 hr.

23
Contraindications cautions Metrifonate
  • Pregnancy.
  • Recent exposure to insecticides / drugs that
    potentiate cholinesterase inhibition.

24
Oxamniquine
  • Semisynthetic tetra-hydro-quinoline
  • PK
  • po
  • T1/2 2.5 hr
  • extensively metabolize into inactive metabolites.
  • excreted via kidney.

25
Anthelmintic actions
  • Effective against mature immature stages of S.
    mansoni ONLY.
  • Its mechanism of action is unknown.
  • It may cause contraction paralysis of worms
    its detachment from the mesentery shift to the
    liver where worm may die.
  • Surviving females may return to mesenteric
    vessels but cease to lay eggs.

26
USES of Oxamniquine
  • Alternative to praziquantel for Tr of all stages
    of S. mansoni ONLY.
  • Effective in praziquantel resistance.

27
Clinical uses
  • Less effective in children (higher doses)
  • better tolerated with food.
  • 15 -20 mg /kg twice for 1 day.
  • In mixed infection with S.H S.M metrifonate
    oxamniquine.

28
Adverse reactions Oxamniquine
  • CNS Dizziness , headache, drowsiness
  • GIT disturbance
  • Pruritus, urticaria, fever
  • Discoloration of urine (orange-red)
  • Proteinuria
  • Transient elevation of liver enzymes
  • Seizures.

29
Contraindications Precautions Oxamniquine
  • Epilepsy
  • Pregnancy
  • Activities require alertness.
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