Antihelmintics Flashcards
1
Q
Niridazole
A
- mechanism: Niridazole is rapidly concentrated in the parasite and inhibits oogenesis and spermatogenesis.
- kinetics: The compound also inhibits the phosphofructokinase enzyme, leading to glycogen depletion
- clinical:schistosomiasis
- toxicity/interactions: Niridazole has central nervous system toxicity and can cause dangerous side effects, such as hallucinations. Also, it may cause allergic reactions in sensitive people. However, it is one of the most effective schistosomicide drugs.
2
Q
Ivermectin
A
- mechanism: Activates GABA receptors leading Cloride channel influx of Cl- leading to worm paralysis.
- kinetics: Oral. Does not cross BBB. Rapid Absorb 4 hours maximum plasma conc. Wide tissue distribution. Excretion in feces.
- clinical: onchocerciasis (river blindness), strongyloidasis
- toxicity/interactions: Mazotti reaction (fever, rash, hypotension, arthralgias, vertigo)
- misc: Contraindicated in meningitis patient because BBB more permeable so CNS effects possible. Also contraindicated in pregnancy. Do not use with drugs that enhance GABA activity ie barbituates
3
Q
Mebendazole
A
- mechanism: inhibits microtubule synthesis and function
- kinetics: Insoluble in aqueous solution. Little of oral dose is absorbed unless taken with high fat meal. Undergoes first pass to inactive compounds
- clinical: roundworm, whipworm, hookworm, pinworm..
- toxicity/interactions: GI upset and allergic reactions
- misc: Contraindicated in pregnant women
4
Q
Metronidazole
A
- mechanism: Metronidazole, taken up by diffusion, is selectively absorbed by anaerobic bacteria and sensitive protozoa. Once taken up by anaerobes, it is non-enzymatically reduced by reacting with reduced ferredoxin, which is generated by pyruvate oxido-reductase.
- kinetics:
- clinical: Structurally similar tinidazole is used for trichomonas and giardiasis. Metronidazole is an antibiotic, amebicide, and antiprotozoal.[1] It is the drug of choice for first episodes of mild-to-moderate Clostridium difficile infection.[
- toxicity/interactions: nausea, diarrhea, and/or metallic taste in the mouth. Intravenous administration is commonly associated with thrombophlebitis. Infrequent adverse effects include: hypersensitivity reactions (rash, itch, flushing, fever), headache, dizziness, vomiting, glossitis, stomatitis, dark urine, and/or paraesthesia.[3]
- misc: Metronidazole is a nitroimidazole antibiotic and has also been used in women to prevent preterm birth associated with bacterial vaginosis
5
Q
Thiabendazole
A
- mechanism: inhibits microtubule synthesis and function
- kinetics: Insoluble in aqueous solution. Absorbed orally. Hydroxylated in liver and excreted in urine.
- clinical: roundworm, whipworm, hookworm, pinworm.. also strongyloidiasis, cutaneous larva migrans, and trichinosis
- toxicity/interactions: GI upset and allergic reactions. Some rare but fatal side-effects see misc.
- misc: Contraindicated in pregnant women. A number of fatalites because of erythema multiforme and stevens johnson syndrome caused by drug
6
Q
Diloxanide
A
- mechanism: Unknown
- kinetics: in gut 90% absorbed and excreted in urine. Unabsorbed is luminally active.
- clinical: amebicide
- toxicity/interactons: low incidence of side effects
7
Q
Niclosamide
A
- mechanism: Inhibit worm production of ATP- kill adults but not ova
- kinetics: Tablets must be chewed
- clinical: Tapeworm except cysticercosis (2nd line)
- toxicity/interactions: GI upset
8
Q
Iodoquinol
A
- mechanism: unknown
- kinetics: 90% drug retained in GI. Rest enter and have half life15 hours, excrete by urine
- clinical: Trophozoites in lumen not intstinal wall or extraintestine
- toxicity/interactions: GI upset
9
Q
Praziquantel
A
- mechanism: Increase Ca++ uptake causing parasite contraction and paralysis
- kinetics: Oral- peak serum conc. 3 hours about 80% drug is bound to plasma proteins
- clinical: Schistosomiasis, neurocysticercosis, hydatid disease and infection by D. latum and clonorchis
- toxicity/interactions: GI upset and elevated LFTs
- misc: Dying “bugs” can cause inflam. response so corticosteroids are given to help relieve some symptoms. Contraindicated in ocular cysticerosis because paracyte distruction of eye can cause perm. damage
10
Q
Pyrantel
A
- mechanism: activates parasitic nicotinic receptors, causes worm paralysis so are expelled with feces
- kinetics: Poorly absorbed orally and effects intestinal tract only
- clinical: Roundworm, hookworm and pinworm
- toxicity/interactions: GI upset (mild)
11
Q
Albendazole
A
- mechanism: inhibits microtubule synthesis and function
- kinetics: Oral dose is absorbed better when taken with high fat meal. Undergoes first pass to sulfoxide which is also active
- clinical: roundworm, whipworm, hookworm, pinworm.. also strongyloidiasis, neurocysticercosis, hydatid disease, cutaneous larva migrans
- toxicity/interactions: GI upset and allergic reactions
- misc: Contrainicated in pregnant women.
12
Q
Piperazine
A
- mechanism: Acetylcholine blocked= paralysis and evenually excreted by parastalsis
- kinetics: absorbed rapidly 2-4 hours orally and excreted in urine
- clinical: ascariasis only
- toxicity/interactions: GI upset
- misc: Contrainicated in pregnant women or renal or hepatic insufficiency or epilepsy or chronic neurological disease
13
Q
Diethylcarbamazepine
A
- mechanism: immobilize microfilarae and render suseptable to host defense.
- kinetics: Oral dose rapid absorption with meals. Excreted in urine. Urine alkalosis or renal imparement require lower dose
- clinical: Filariasis. with albendazole and diethylcarbamzine trats wuchereria bancrofti and brugia malayi. The worms that cause blockage of lymph flow.
- toxicity/interactions: Adverse reactions are to dead organism, equivalent to load. Fever, malaise, rash, myalgias, arthralgias, headache.
- misc: Most patients have leukocytosis. Antihistamines or steroids can relieve many symptoms. Used with ivermectin or albendazole
