Antiparasitic Drug Classification: Quiz and Flashcards

Study Notes

Anthelmintics

Anthelmintics are drugs with the property of ridding the body of parasitic worms and act by either destroying the helminths or expelling them from the infested patient.
There are two main classes of helminths: Nematodes (roundworms, hookworms, whipworms, and threadworms) and Platyhelminthes (flatworms, including tapeworms).

Sources of Infestations

Contact with infected animals
Ground contaminated by human or animal excrement
Water infested with cercariae
Ingestion of infested meat

Treatment

Selection of drug is important due to attendant side effects
Stool examination is crucial for identification of the worm
Hygiene is the most important key to prevention

Chemotherapy Classes of Anthelmintics

Chlorinated Hydrocarbons (e.g., tetrachloroethylene)
Phenol and derivatives (e.g., Niclosamide)
Piperazine and derivatives (e.g., Diethylcarbamazine)
Heterocyclic compounds (e.g., Mebendazole, thiabendazole)

Piperazine Derivatives

Piperazine is used to treat threadworms and roundworms
It blocks the response of ascaris muscle to acetylcholine, causing flaccid paralysis of the worm
Diethylcarbamazine (DEC), a piperazine derivative, is used for filariasis, ascaris, and river blindness

Mebendazole

Mebendazole is a broad-spectrum anthelmintic effective against various nematode infestations
It irreversibly blocks glucose uptake in susceptible helminths, depleting glycogen stored in the parasite

Albendazole

Albendazole is a broad-spectrum anthelmintic
It is effective as a single-dose treatment for ascariasis
It undergoes rapid and extensive first-pass metabolism to the sulfoxide, which is the active form in plasma

Thiabendazole

Thiabendazole is a broad-spectrum anthelmintic with activity against enterobiasis, threadworm, ascariasis, hookworm, and whipworm infections
It inhibits the helminth-specific enzyme fumarate reductase

Niclosamide

Niclosamide is a potent taeniacide that causes phosphorylation in the mitochondria, interfering with vital life processes
It is used to treat tapeworm infections

Pyrantel

Pyrantel is the drug of choice against infestations with ascaris and enterobius
It inhibits worm's acetylcholinesterase, causing spastic paralysis in susceptible helminths

Amoebicides

Amoebiasis is a protozoal infection of the intestine (Intestinal amoebiasis) and sometimes the liver (Hepatic amoebiasis) caused by Entamoeba histolytica
The parasite exists in two forms: the active parasite (trophozoite) and the dormant parasite (cyst)

Chemotherapy for Amoebiasis

Nitroimidazoles are the drugs of choice for both intestinal and systemic amoebiasis
They are also useful in trichomoniasis, schistosomiasis, giardiasis, cutaneous leishmaniasis, acute ulcerative gingivitis, and Trichomonas vaginalis
Examples include Metronidazole, Tinidazole, Ornidazole, Secnidazole, Nimorazole, and Niridazole

Mechanism of Action of Nitroimidazoles

Antibacterial and antiprotozoal, with microbicidal activity against most obligate anaerobic bacteria and protozoa
Mechanism is mediated through oxidative reactive species
Reduced metronidazole (2-hydroxy metabolite) interacts with DNA to cause a loss of helical structure, strand breakage, and resultant inhibition of nucleic acid synthesis and cell death

Description

Test your knowledge on antiparasitic drugs effective against histolytica cysts in faeces, such as metronidazole and tinidazole. Learn about the classification of helminths like Ascaris lumbricoides, Ancyclostoma duodenale, Strongyloides stercolaris, and Enterobius vermi. Understand the essential process of ester hydrolysis for drug activity.