This document summarizes intestinal infection by Entamoeba histolytica. It describes the life cycle of the parasite including ingestion of cysts, the luminal and tissue phases, and potential for extra-intestinal infection. It provides details on classification and treatment of intestinal and extra-intestinal amoebiasis with nitroimidazoles like metronidazole, tinidazole, and secnidazole. It also discusses other luminal and tissue amoebicides as well as treatments for related parasitic infections including giardiasis, trichomoniasis, trypanosomiasis, and toxoplasmosis.

2. Intestinal infection - Entamoeba histolytica
 Ingested cysts through food water
 Poor environmental sanitation
 Low socio-economic status
 Many patients are asymptomatic
 Characterized by diarrhea, weakness


4. Luminal Phase
Cysts in Faeces – propagation of
disease.
 Tissue phase
Ulcer /dysentery
Abscess
 Extra intestinal
Lung, Spleen, Kidney, Brain


5. Classification
 Tissue Amoebicides
 Extra intestinal & Intestinal
Nitroimidazoles Metronidazole
Tinidazole
Secnidazole
Ornidazole
satranidazole
Alkaloids
Emetine
Hydroemetine
 Extra intestinal amoebiasis only
SHOULD always be followed by Luminal
Chloroquine
amoebicide to eradicate source of infection

6. 
Luminal amoebiasis
Amide
8-Hydroxy quinolones
Antibiotics
Diloxanide furoate
Quinidochlor
Diiodohydroxyquin
Tetracycline

7. Metronidazole
Nitroimidazole group, Prototype drug
introduced in 1959
 It active aganist amoebae, anaerobic
bacteria and certain helminthis
 PK:- Oral & parental
 Absorption occurs in proximal intestine
 Well distribution, therapeutic level it found in
vaginal, seminal fluid, CSF, saliva and milk
 Metabolized by oxidation and glucuronidation
 t½-8hrs.
 Not given pregnancy


8. MOA:
Enters micro-organism by diffusion
PFOR enzyme act as electron removal
(Pyruvate ferrodoxin oxido reductase)
Nitro group serves as electron acceptor reduced
Cyto toxicity
DNA Damaged

9. Clinical uses
DOC for tissue amoebiasis
 Cysts passers Metroindazole + Diloxanide furoate
 Moderate intestinal amebiasis 400mg orally TDS 5-7days
 Amoebic dysentry , liver abcess 800mg TDS for 7days
 Giradiasis- 200mg TDS for 7days
 Trichomonas vaginitis -400mgTDS for 7days
 Anaerobic bacterial infections brain abscess, endocarditis
 Psudomembranous colitis – 500mg TDS
 Ulcerative gingivitis, Stomatitis- Metro+ tetracycline
 Guinea worm , eradicating H.Pylori


10. Adverse Drug Reactions
 Frequent
○ Anorexia, nausea
○ Metallic taste, abdominal cramps
○ Dark red brown urine
• Less frequent
○ Headache, dry mouth,
○ dizziness, rashes
○ neutropenia

On prolonged administration
○ Peripheral neuropathy, CNS effects

11. Contraindications
 Neurological diseases, blood dyscrasias,
 First trimester, Chronic alcoholism(ADH Inhibition)
Drug Interactions
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Disulfiram reaction
Enzyme inducers - Rifampicin -↓therapeutic
effect
Cimetidine - ↓metronidazole metabolism reduce
dose
Metronidazole ↓renal elimination of Lithium
Warfarin ↓renal elimination

12. Tinidazole
Slower metabolism – longer duration action –
Given OD
 Better tolerated
 Use in amoebiasis – 600mg BD X 7 days
 Trichomoniasis, Giardiasis 600mg for 7days
Secnidazole – longer duration
 2g single dose
 Less side effects


13. Emetine
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Alkaloid from Cephaelis ipecacuanha
MOA: Protein synthesis inhibitor
Potent directly acting amoebicide (trophozoites)
Does not kill cysts
Toxicity high –Seldom used
Reserve drug – not responding/intolerant to
metronidazole
Luminal amoebicide follows emetine to eradicate cysts
Dihydroemetine =effective but less toxic
 Preferred over emetine

14. Chloroquine
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Kills trophozoites
Concentrates in liver Used in hepatic amoebiasis
Rx duration longer 500mg x 21days
Relapses more frequent than emetine
Resistance doesn’t develop
Luminal amoebicide must always be given with or
after Chloroquine to abolish luminal cycle
Dose in liver abcess -600 mg(base) X
2days,300mg X 2-3 weeks
Reserved drug only used metronidazole is not
tolerated

15. Diloxanide furoate
Highly effective luminal amoebicide
 Directly kills trophozoites
 No anti bacterial action
 Drug of Choice for mild intestinal/
asymptomatic amoebiasis
 Given after tissue amoebicide to eradicate
cysts
 Given in combination with metronidazole OR
tinidazole
 ADRs – pruritis, urticaria, flatulance


16. 8-hydroxy quinolone
Once widely used luminal amoebicide
 Rarely now because neuritis & optic damage
 Uses: luminal amoebicide, giardiasis
 Locally for monilial/trichomonas vaginitis,
fungal & bacterial infections
 ADR:- green colored stool
 Prolong use case iodine overload (Goiter)
 Not safer drug for pregnancy and children


17. Tetracycline
 Directly inhibit amoebae but only at high
concentration.
 ↓bacterial flora
 Used along with other luminal agents
 Adjuvant in chronic difficult to treat cases

18. GIARDIASIS
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Giardia lamblia, Pear shaped
Two nuclei and four flagella
Attach to intestinal mucosa
From they absorb nourishment & interfere
absorption
Characterized by watery diarrhea & malabsorption
Metroindazole 200mg TDS 7days
Tinidazole 600mg daily 7days
Secnidazole 2g single dose

19. TRICHOMONIASIS

Gential infection produced by Trichomonas
vaginalis

Metroindazole 400mg TDS 7days or 2g single
dose
Tinidazole 600mg daily 7days or 2g single dose
Secnidazole 2g single dose
Nimorazole 2g single dose with meals


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* Repeat course may given after 6 weeks

20. TRYPANANOSOMIASIS
Africian Trypnosmiasis :- T. brucei
Two stages –

Haemolymphatic – enlargement of lymph node
 Meningo encephalopathic – mental distrubance,
diziness (Sleeping
sickness)
 Early- Sumarin or pentmidine
 Late CNS – Melarsoprol


21. American trypanosomiasis(Chagas’
disease)
 T.Cruzi
Cardiomyopthy

Mega colon- mega esophagus &
gastrointestinal lesions
Nifurtimox: MOA: free radical generator

22. Toxoplasmosis
Toxoplasma gondii
 Pyrimethamine+ Clindamycin+ Folinic
acid
 Pyrimethamine + sulfadiazine


23. Thank