Antiprotozoal drugs are a class of medication used to treat infections caused by protozoa, which are single cell organisms that belong to the type of parasites.  Although Protozoal infections occur throughout the world and are a major cause of morbidity and mortality in some regions such as Africa and South-East Asia. In the United States and other countries of the temperate zone, protozoal diseases are of minor importance. Protozoal diseases are highly prevalent in tropical Third World countries, where they infect both human and animal populations.

1. Medicinal Chemistry-III
Anti-protozoal agents
Department of Pharmacy, Indira Gandhi National Tribal
University, Lalpur, Amarkantak (M.P.)
Dr. Akhilesh Tiwari
Assistant Professor
Department of Pharmacy,
IGNTU, Amarkantak
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2. Introduction
Antiprotozoal drugs are a class of medication used to treat
infections caused by protozoa, which are single cell organisms
that belong to the type of parasites.
Although Protozoal infections occur throughout the world and are
a major cause of morbidity and mortality in some regions such as
Africa and South-East Asia.
• In the United States and other countries of the temperate zone,
protozoal diseases are of minor importance.
• Protozoal diseases are highly prevalent in tropical Third World
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3. Different Types of Protozoa
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4. Overview of Protozoal Infections
- Definition: Protozoa are single-celled microscopic organisms belonging to the
kingdom Protista.
- Classification: Protozoal infections are caused by various protozoa species,
classified based on their mode of movement (e.g., amoeboid, flagellar,
ciliated).
- Examples: Common protozoal infections include amoebiasis, giardiasis,
- malaria, leishmaniasis, and toxoplasmosis.
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5. Importance of Effective Treatment
Health Impact: Protozoal infections can cause a wide range of symptoms, from mild
gastrointestinal discomfort to life-threatening complications such as severe dehydration,
organ damage, and neurological disorders.
Transmission: Protozoa can be transmitted through various routes, including contaminated
food or water, insect vectors (e.g., mosquitoes, flies), and direct contact with infected
individuals or animals.
Public Health Concerns: Protozoal infections pose significant public health challenges due to
their ability to spread rapidly within communities and their potential to cause outbreaks or
epidemics.
Importance of Treatment: Effective treatment is crucial for controlling the spread of
protozoal infections, reducing morbidity and mortality, and improving overall public health
outcomes.
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6. CLASSIFICATION ANTIPROTOZOAL AGENTS
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7. METRONIDAZOLE
1. Metronidazole:
Mechanism of Action: Metronidazole is a nitroimidazole antibiotic that acts
by entering protozoal cells and undergoing chemical reduction by
intracellular electron transport proteins. This reduction process results in
the formation of reactive nitro radicals, which subsequently damage the
DNA of the protozoa, leading to inhibition of nucleic acid synthesis and
ultimately cell death.
Clinical Indications: Metronidazole is commonly used to treat a variety of
protozoal infections, including amoebiasis, giardiasis, trichomoniasis, and
certain anaerobic bacterial infections.
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8. MECHANISM OF METRONIDAZOLE
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9. 2. Tinidazole:
Mechanism of Action: Tinidazole, like metronidazole, is a nitroimidazole
antibiotic. It exerts its anti-protozoal activity by undergoing reduction
within protozoal cells, leading to the generation of toxic radicals. These
radicals cause DNA damage and disrupt nucleic acid synthesis,
ultimately resulting in the death of the protozoa.
Clinical Indications: Tinidazole is used to treat similar protozoal
infections as metronidazole, including amoebiasis, giardiasis,
trichomoniasis, and certain anaerobic bacterial infections.
Tinidazol
e
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10. Ornidazole
3. Ornidazole
Ornidazole inhibits the growth of protozoa by interacting with the DNA of the micro-organism and inhibiting
the protein synthesis, thereby leading to death of the micro-organism.
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11. Iodoquinol
4. Iodoquinol:
Mechanism of Action: Iodoquinol interferes with the metabolism of
protozoa by inhibiting nucleic acid synthesis and disrupting the function
of the electron transport chain. It exerts its anti-protozoal activity by
binding to DNA and interfering with its replication and transcription
processes.
Clinical Indications: Iodoquinol is commonly used in the treatment of
amoebiasis and other intestinal protozoal infections.
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12. Pentamidine Isethionate
5. Pentamidine Isethionate:
Mechanism of Action: Pentamidine isethionate inhibits nucleic acid synthesis and protein
synthesis in protozoa. It disrupts the function of enzymes involved in these processes,
ultimately leading to the death of the parasite.
Clinical Indications: Pentamidine isethionate is used in the treatment of African
trypanosomiasis, leishmaniasis, and Pneumocystis jirovecii pneumonia.
These mechanisms of action highlight the diverse strategies employed by anti-protozoal
agents to target and eradicate protozoal infections. Understanding these mechanisms is
essential for selecting the appropriate medication and optimizing treatment outcomes.
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13. Common adverse reactions- cough and bronchospasm (inhalation) and
hypertension and hypoglycemia (injection)
Used for the prophylaxis and treatment of African trypanosomiasis. It
also has some value for treating visceral leishmaniasis
Prophylaxis- treatment given or action taken to prevent disease
Because, Pentamidine rapidly disappears from the plasma after
intravenous injection and is distributed to the tissues, where it is stored
for a long period
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14. Atovaquone
6. Atovaquone:
Mechanism of Action: Atovaquone is a hydroxynaphthoquinone that selectively inhibits
mitochondrial electron transport in protozoa. By disrupting the function of the electron
transport chain, atovaquone interferes with the production of adenosine triphosphate (ATP),
which is essential for the survival of the protozoa. This disruption ultimately leads to the
death of the parasite.
Clinical Indications: Atovaquone is primarily used in the treatment of malaria, both in
uncomplicated cases and as prophylaxis. It is also effective against Pneumocystis jirovecii
pneumonia.
•It is extensively protein bound (99.9%)
•Half-life of the drug ranges from 62 to 80 hours
•Primary side effect is gastrointestinal intolerance
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15. Eflornithine
7. Eflornithine
Mechanism- irreversible inactivation of ornithine decarboxylase by eflornithine
is accompanied by decarboxylation and release of fluoride ion
Enzyme is involved in the synthesis polyamines which are regulators of growth
processes
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16. Diloxanide
8. Diloxanide
• 2-furoate ester of 2,2-dichloro-4-hydroxy-N-methylacetanilide
• It was developed as a result of the discovery that various ,α-α-dichloroacetamides
possessed amebicidal activity in vitro
• Used in the treatment of asymptomatic carriers of E. histolytica
• White crystalline powder and is administered orally only as 500-mg tablets
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17. METRONIDAZOLE- SYNTHESIS
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