7 - Anthelminthics Flashcards
Classification of Anthelminthics
Vermicide (kill) and Vermifige (expel)
Complete elimination of parasites (helminthic infections) can be challenging because….
limited drug efficacy and frequent reinfection after therapy
Strongyloides and Echinococcus are..
The only helminths that can complete their life cycle and unable to replicate themselves in the human host
The major soil-transmitted helminth infections are..
Ascariasis, trichuriasis, and hookworm (Ancylostoma duodenale)
General MoA of anthhelmintics
Inhibiting energy production and targeting neuromuscular system
Anthelmintics may result in..
Spastic paralysis (e.g. metrifonate, praziquantel, and pyrantel pamoate) and flaccid paralysis (e.g. ivermectin and piperazine)
Benzimidazoles have excellent safety profiles, except for…
Thiabendazole, because it has more side and adverse effects
Primary MoA of Benzimidazoles
Inhibit microtubule polymerization by binding to beta-tubulin –> Interfere cell division of helminths (selective toxicity due to higher binding affinity than humans)
Albendazole is clinically used for..
Local infection (intraluminal parasites), systemic infection (tissue parasite), neurocysticercosis (lead to helminth seizure), hydatid disease, ascariasis, trichuriasis, and hookworm infections
Mebendazole should be administered..
With a fatty meal to increase absorption and tablets should be chewed before swallowing
Thiabendazole is an alternative to..
Ivermectin and Albendazole
Bithionol is used as..
Alternative treatment for fascioliasis & pulmonary paragonimiasis through uncoupling of oxidative phosphorylation
Bithionol is used as..
Alternative treatment for fascioliasis & pulmonary paragonimiasis through uncoupling of oxidative phosphorylation
Diethylcarbamazine citrate is a drug of choice in the treatment of..
Filariasis, loiasis, and topical eosinophilia
MoA of diethylcarbamazine citrate
Immobilizes microfilariae + alter surface structure –> tissue displacement –> increased destruction susceptibility
To reduce the prevalence of W. Bancrofti infection, diethylcarbamazine citrate is combined with..
Ivermectin / Albendazole
Indication of Ivermectin
Drug of choice in strongylodiasis and onchocerciasis and alternative drug for several helminthiasis
MoA of Ivermectin
Intensifying GABA-mediated transcription of signals in peripheral nerves –> flaccid paralysis –> blocks microfilariae release (not kill adult worms)
Metrifonate (Trichlorfon) indication
Alternative drug for schistosoma haematobium infections
Metrifonate MoA
Inhibit cholinesterase –> accumulation of ACh –> Continuous spasm –> spastic paralysis in adult worms –> move to small arterioles of lungs –> killed by immune system
For mixed infections with S. haematobium and S. mansoni, metrifonate is combined with..
Oxamniquine
Niclosamide indication
Second-line treatment for most tapeworm infections
Niclosamide MoA
Inhibition of oxidative phosphorylation/Stmulation of ATPase activity –> rapid helminth death
Niclosamide is taken..
In the morning on an empty stomach and must be chewed thoroughly
Oxamniquine indication
Alternative to praziquantel for treating S. mansoni
MoA of Oxamniquine
Contraction and paralysis of the worms –> Detachment from terminal venules in the mesentery and transit to the liver
Piperazine indication
Alternative treatment to ascariasis, cure rates over 90%
MoA of piperazine
Block acetylcholine at myoneural junction –> causes paralysis of ascarsis –> worms expelled by peristalsis
Praziquantel indication
Treatment of schistosome infections + trematode and cestode infections
Praziquantel plasma concentration increases when
Taken with high-carb meal or with cimetidine
MoA of Praziquantel
Increase permeability of trematode and cestode cell membranes to calcium –> parasite contraction (spastic paralysis) –> worm loses grip in GIT and expelled
Praziquantel tablets are taken..
After a meal and swallowed without chewing because of bitter taste (induce retching and vomiting)
Pyrantel pamoate indication
Pinworm, ascarsis, and Trichostrongylus orientalism infections, and both hookworm species (moderate effectiveness)
Pyrantel pamoate
Disturb nerve function junction –> inducing activation of nicotinic receptor –> release of acetylcholine / cholinesterase inhibition –> acetylcholine accumulation –> spastic paralysis –> paralyzed worms expelled
Doxycycline indication
Onchocerciasis and macrofilaricidal activity against W. bancrofti
