Anti-Helminthics And Anti-Protozoals

Question 1

Metronidazole

Answer 1

• originally an antiprotozoal agent
• under anaerobic conditions it generates toxic radicals that damage bacterial and protozoal DNA
• active against Entamoeba Histolytica and Giardia Lamblia.
• penetrates well into tissue, hence its value in amoebic liver abscess
• metalic taste is common and can be hard to tolerate
• cause an acute nausepus reaction with alcohol.

Question 2

Tinidazole

Answer 2

-treats giardia lamblia

Question 3

Paromycin

Answer 3

• used in cryptosporidial treatment
• an aminoglycoside
• given orally
• not absorbed from GI tract
• kills amoebic cystic stage
• adverse events include abdo cramps, diarrhoea, heartburn, nausea, and vomiting.

Question 4

Nitazoxanide

Answer 4

-Used in cryptosporidial treatment

Question 5

Spiramycin

Answer 5

Used in cryptosporidial treatment

Question 6

Diloxanide Furoate

Answer 6

• a luminal amoebicide.
• flatulence, itchiness, and hives are associated with use
• usually well tolerated with minimal toxicity
• on WHO essential medicine list

Question 7

Oral Rehydration Therapy

Answer 7

• involves the replacement of fluids and electrolyes lost during diarrhoeal illness.
• 90-95% of cases of acute, watery diarrhoea can be successfully treated with an oral rehydration solution (ORS).
• ORS increases the resorption of fluids and salts into intestinal wall.
• ingredients; glucose (anhydrous) 13.6g/L, NaCl 2.6g/L, KCl 1.5g/L, Trisodium citrate dihydrate 2.9g/L.
• in addition, fruit juices, coconut water, and other indigenous solution can adequately approximate ORS.

Question 8

Praziquantel

Answer 8

• mode of action not fully known - probably increases calcium permeability of membranes depolarising them or may interfere with purine synthesis.
• treatment for hydatid disease, cysticercosis, schistosomiasis, clonorchis, fascioliasis, and paragnomiasis infection.
• well absorbed orallt
• 20mg/kg
• on WHO essential medicine list
• Significant first pass effect
• low systemic concentrations
• excreted in the kidneys
• short half life
• can cause dizziness, headache, drowsiness, somnolescence, rarely seizures, abdo cramps, nausea, diarrhoea, transient asymptomatic rise in transaminases, urticaria, rash, pruritis.
• interacts with rifampicin (decreased concs), carbamazine, phenytoin (reducing praziquantel bioavailability).

Question 9

Diethylcarbamazine (DEC)

Answer 9

• a piperazine derivative
• on WHO essential medicine list
• inhibits arachidonic acod making parasites more susceptible to immune attack
• filaria infection
• associated with increase in inflammation: caution Mazzotti reaction, loss of site in onchocerciasis.

Question 10

Ivermectin

Answer 10

• binds glutamate-gated chloride increase in the permeability of the cell membrane to chloride ions with hyperpolarisation of the nerve or muscle cell resulting in paralysis and death of the parasite either directly or by causing them to starve.
• active against fliarial worms, lice, scabies amd bed bugs.
• currently used for eradication of lymphatic filariasis and onchocerciasis.
• contraindicated in children under 5 or breast feeding mothers.
• Complicated by CNS depression.
• Increased risk of absorption past the blood brain barrier of HIV protease inhibitors, calcium channel blockers and glucocorticoids.

Question 11

Albendazole

Answer 11

• treatment for nematode infections - trichiuriasis, filariasis, enterobius infection, ascariasis, hookworm, toxocariasis, strongyloidiasis.
• treats giardia lamblia
• treatment of some cestode infections - neurocysticercosis, hyatid disease
• on WHO essential medicine list
• mode of action - binds to colchicine sensitive receptor or tubulin, this prevents polymerisation into microtubules, impaired glucose uptake and depleted glycogen stores, degenerative changes appear in the worm.
• concentrated in semen and may be teratogenic
• side-effects - persistent sore throat, headaches, dizziness, seizures, acute liver failure, aplastic anaemia and marrow supression.

Question 12

Mebendazole

Answer 12

Treats threadworm (enterobius vermicularis), hookworm (ancylostoma and necator), whipworm (trichuris trichiura)

Question 13

Pyrantel Pamoate

Answer 13

• treatment of hookworms and roundworms
• causes depolarising neuromuscular blockade
• poorly absorbed providing selective toxicity
• excreted unchanged in the faeces
• antagonistic with piperazine
• avoid in pregnancy
• can cause intestinal obstruction of there is a heavy worm load.

Question 14

Approach for treating Helminth Infections

Answer 14

• Inflammation - anti-inflammatory e.g. steroids
• Competition for nutrients - reduce worm burden and support nutrition
• Space occupying lesions - surgery, decompression
• Stimulation of fibrosis - helminth eradication and treatment of secondary effects

Question 15

Levamisole

Answer 15

• on the WHO list of essential medicine
• nicotinic acetylcholine receptor antagonist
• treats ascariasis and mixed ascaris hookworm infection
• rapidly absorbed
• caution in pregnancy
• abdompain, nausea and vomiting are reported

Question 16

Piperazine

Answer 16

• agonist activity against gamma butyric acod receptor paralysing muscular activity
• orally active
• metabolism in liver
• variable half life
• used tp treat ascariasis and enterobius infection
• side-effects - GIT upset, rarely hypersensitivity and dizziness.

Question 17

Niclosamide

Answer 17

• inhibits glucose uptake, oxidative phosphorylation and anaerobic metabolism
• used for treatment of tapeworm infections only
• causes dizziness, skin rashes, drowsiness and perianal itching.

Question 18

Surgery

Answer 18

Used when there are space occupying lesions caused by helminthic infections or when the worms cause an intestinal obstruction.