7 - Anthelmintic Drugs

1

ANTHELMINTIC DRUGS

DR.ABDUL LATIF MAHESAR

Department of Medical Pharmacology

KSU

2

INTRODUCTION Humans are the primary hosts for the most of

helminthic infections.

Most worms produce in human sexually by producing eggs and larvae

These pass out of body and infect the secondary host Imature forms invade humans via skin or GIT and

mature to adult worms with characterstic tissue distribution.

3

Types (clinical)

1. Worms live in hosts alimentary canal.

2. Worms or larvae live in other tissues of host

body like muscles , viscera , menninges ,

lungs, subcutaneous tissues.

4

INTESTINAL WORMS CON’D

A) INTESTINAL ROUND WORMS (NEMATODES)

Ascaris lmubricods (common round worm) Enterobius vermicularis (pin worm) Trichuris trichuria ( whip worm) Strongyloids stercoralis ( thread worm) Ankylostoma dudenale (hook worm)

5

Ascaris lumbricoids ( common round worm)

6

Hookworm

7

Pinworm male ,female

8

whipworm

9

Tricuris tricura(whip worm)

10

1. Alimentary canal(intestinal tape worms)

B) TAPE WORMS (CESTODES) Taenia saginata(Beaf) , Taenia solium(Pork),Hymenolepis nana(Dwarf)

,diphylobothrium latum(Fish) Humans become infected by eating raw or

under cooked meat containing larvae of infected cattle or pig which has encysted in the animal muscle tissue.

11

Cestodes con’d In some conditions this larvae may develop in

humans resulting cysticercosis (i.e. larvae gets encysted in the muscle and viscera or more seriously in the brain or eye.)

In case of H.nana both adult worm and larvae can be present in the same host.

In case of D.latum infections occurs by eating raw or undercooked fish

12

Tapeworm

13

cysticercosis

14

2. TISSUE WORMSA.TREMATODES(Schisotomes)OR FLUKES(leaf like)

Schistosoma haematobium Schistosoma Japonicum Schistosoma mansoni (These cause SCHISTASOMIASIS) also called

(BILHARZIA) means disease of blood vessels. Adult worms of both sex live and mate in veins or

venules of the gut wall or the bladder, eggs pass into the bladder or gut and produce inflammation of these organs , resulting in haematuria or loss of blood in feces.

15

Tremtodes (flukes) con’d

Eggs hatch in water and develop in to miracidia(1st stage of larva of trematode and further develop in the body of snail), which enter to 2ndry host a particular species of snail ,where it develops to free swimming cercarae (final free-swimming stage of a trematode),These infect humans by penetrating to skin

Paragonimus westermani (lung fluke)disease is caused by eating raw crab or fish , larvae move from intestine to blood and settle in lungs

Clonorchis sinensis(liver fluke)disease is caused by eating raw fish and worm settle in the biliary tract

16

17

Tissue worms cont’d

B. TISSUE ROUND WORMS

Trichnella spiralis.

Dracunulus medinensis (guinea worm)larva migrate from intestine to tissue of leg or foot and protrude out by making ulcer

FILARIAE includes

Wuchereria bancrofti

Loa loa

Onchocerera volvulus

Brugia malayi

18

19

Trichinela spiralis

20

21

22

filariasis

23

Wuchereria or Brugia obstructs lymphatic vessels producing elephantiasis

elephantiasis

24

Filariae: Wucheria bancrofti ,loa loa , onchocera volvulus and Brugia malayi

Adult filariae live in the lymphatics,and cause lymphadenitis and swelling of limb. connective tissue or mesentery of host and produce live embryos or microfilariae, which goes to blood stream.

They are ingested by mosquitoes or similar insects, they develop to larvae in 2ndry host and pass to mouth parts of insect and

re-injected to humans

25

C. Hydatid tape worm

Echinococcus species .

These are cestodes ,primary in canines (dogs) and sheep as intermediate host.

humans can act intermediate host in which larvae develop to hydatid cyst with in tissue.

26

Hydateid cyct

27

Helminths commonly infecting manNematodes( round worm)Tissue worms wuchereria bancrofti Filariasis

Brugia malayi FilariasisLoa loa loiasisOnchocerca River blindnessDracunculus medinensis Dracunculiaiss

Intestinal human nematodes Enterobius vermicularis Threadworm

Ascaris lumbricoides RoundwormTrichuris trichiura WhipwormNector americanus HookwormAncylostoma duodenale Hookworm

Strongyloides stercoralis StrongyloidosisTrematodes(flukes)

Blood flukes Schistosoma species Schistosomiasis

Lung flukes Paragonimus speies Paragonimiasis

Intestinal / hepatic flukes Fasciolopsis buskiFasciola hepaticaClonorchis sinensis

28

Helminths commonly infecting man cont’dCestodes(tapeworms)Intestinal adult worms Taenia saginata Beef tapeworm

Taenia soliumPorktaperworm

Diphyllobothrium latumFishetapeworm

Hymenolepis nanaDwarftapeworm

Larval tissue cysts Taenia solium cysticercosisEchinococcus granulosus Hydatid

diseaseEchinococcus multilocularis Hydatid

disease

Spirometra mansoni Sparganosis

29

Diseases caused by filarial wormsOrganism adult worm Microfilariae C.signsW. bancrofti Lymphatics Blood Fever

lymphangitis Elephantiasis

B.Malayi lymphatics Blood Fever lymphangitis Elephantiasis

Loa loa Subcutaneous Blood Urticaria

Onchocerca Subcutaneous skin,eye subcut nodules Eye disease

Mansonella perstans Retroperitoneal Blood Allergic eosinophilia

30

Dircrocoelium dendriticum

31

Fasiola hepatica

32

ANTHELMINTIC DRUGS

BENZIMIDAZOLES1.ALBENDAZOLE:

It is a broad spectrum It is a drug of choice (primary therapeutic

application) for treatment of hydatid disease and cystecercosis, it is also used for the treatment of (intestinal nematodes) ascariasis ,tricurasis and strongyloidiasis , pinworm, hookworm

33

Albendazole con;d

Mechanism of action: It inhibits microtubule synthesis in nematodes(intestinal round worms) that irreversibly impairs glucose uptake, intestinal parasites are immobilized and die slowly.

It is larvicidal in hydatid ,cysticercosis , ascariasis and hook worm infection.

Also ovicidal in ascariasis , ancyclostomiasis(hookworm) , tricurasis

34

Pharmacokinetics (Albendazole)

It is benzimidazole carbamate

it is adminstered orally , and absorbed erratically (unpredictable) , absorption can be increased with fatty meal

It is metabolized in the liver rapidly to active metabolite albendazole sulphoxide

35

Pharmacokinetics (Albendazole)

It has a plasma half life of 8-12 hours

Sulphoxide is mostly protein bound , distributes well to tissues and enters bile, csf, hydated cyst

Metabolites are excreted in urine

36

Clinical uses (albendazole)

used on empty stomach when used against intraluminal parasites but with fatty meal when against tissue parasites.

In ascariasis ,tricurasis ,hookworm, pin worm infection : children under 2 years 400 mg orally as a single dose repeated for 2-3 days in heavy ascariasis ,repeated after 2-3 wks for pin worm

2. Hydated diseases: drug of choice ,400 mg twice with meals for 1

month or longer.

37

Albendazole con’d

3. Neurocysticercosis: It is controversial as it has not proved superior to corticosteroid alone.

It is used along with cotricosteroid to decrease the inflammation caused by dying organism and it also reduces the duration of course i.e. 400 mg twice daily for 21 days

4. Other infections: Drug of choice in cutaneous and visceral larvea migrans , intestinal cappillariasis and others

38

Albendazole con’d

Adverse effects: In short term: use no significant adverse effects.

In long term use : as used in hydatid cyst and cysticercosis, abdominal distress, headache ,fever , fatigue, alopecia , increased liver enzymes , pancytopenia. Blood counts and LFT should be followed.

Not given during pregnancy and in hypersensitive people.

39

MEBENDAZOLE(Vermox) it is a synthetic benzimidazole it has wider spectrum and is more safer than

albendazole

Mechanism of action:It inhibits microtubule synthesis in nematodes that

irreversibly impairs glucose uptake.Intestinal parasites are immobilized and die slowy.

It kills hook worm, pin worm , ascariasis and trichuris eggs.

40

Mebendazole con’t

Pharmacokinetics: less than 10% of orally administered drug is absorbed Absorption increases with fatty meal. Absorbed drug is 90 % protein bound It is converted to inactive metabolites rapidly in liver. It has half life of 2-6 hours It is primarily excreted in urine.

41

Mebendazole con’t

Clinical uses:

It is taken orally before or after meal tablets should be chewed before swallowing.

Pinworm infection: 100 mg as a single dose, to be repeated after 2-3 weeks.

Ascaris lumricoides , trichuris trichura , hookworm and trichstrongtlus; 100 mg /twice daily for 3 days to repeated in 2-3 weeks

in adults and children over 2 years cure rate is 90-100 % except hook worm but there occurs marked reduction

42

Mebendazole con’d

Intestinal cappilliaris: 400 mg /day in divided doses for 21 day or more.

Trichinosis :it has limited efficacy against adult worm.200-300 mg for 3 days ,then 400-500 mg for 10 days with fatty meal and co-administration with corticosteroids in sever infection

43

Mebendazole con’dAdverse effects and precautions:

No adverse effects in short term therapy.Mild GI disturbance.

With high dose Hypersensitivity reactions,agranulocytosis , alopecia ,elevation of liver enzymes .

used with caution under 2ys of age may cause convulsion in this group.

enzyme inducers and inhibitors affect plasma level of the drug.

hepatic parenchymal disease

44

Thiabendazole it is benzimidazole

it is chelating agent and form stable complexes with metals including iron, but does not bind with calcium.

it is rapidly absorbed

it has half life of 1.2 hrs

It is completely metabolized in liver and 90% is excreted in urine

it can also get absorbed through skin

45

Thiabendazole con’d: mechanism of action: similar to other benzimidazoles.It

is ovicidal for some paracites clinical uses: should be given after meals .and tablets should be chewed

for strongyloides(thread worms) infections: 25 mg /kg ( not more than 1.5 grams) twice daily for 2 days ,can be repeated after 2 week. In hyper infection syndrome drug is continued twice daily for 5-7 days.

for cutaneous larval migrans thiabendazole cream is applied topically or drug can be given orally for 2 days.

46

Thiabendazole con’d

adverse reactions and contraindications: It is more toxic than other benzamidazoles GI disturbances Pruritus ,headache, drowsiness , psychoneurotic

symptoms. Irreversible live failure. Fatal Steven –Johnson syndrome(inflammation of skin) Not used in children below 15 kg weight. pregnancy,

hepatic and renal diseases.

47

PYRANTEL PAMOATE It is a broad specturm anthelmintic but it is not effective against tricuriasis(whip worms), and

trichostrongylus orientalis infections. Oxalate pamoate is effective

Pharmacokinetics: It is poorly absorbed orally , Half of the drug is excreted unchanged in the feces. Mechanism of action: It is a depolrazing neuromuscular blocking agent that

causes release of acetylcholine and inhibition of cholinestrase leads to paralizes of worms.

48

Pyrantel pamoate con’dEfficacy and clinical uses: it is very effective against luminal organisms. It is not effective against migratory stages in the tissues or against

ova

Entrobius vermicularis (pin worm) 11 mg /kg as a single dose to be repeated in 2 wks.

Ascariasis lumbricoids (common round worm).single dose to be repeated after 2wks

Ankylostoma dudenale (hook worm) single dose for light infection but a 3 days course is necessary for heavy infection.especially N amerianus.

49

Pyrental pamoate con’d Adverse Effects . Infrequent mild transient GI disturbance drowsiness , headache ,insomnia. Rash ,feverContraindciations Should not be used in liver diseases. Pregnancy and child under 2 years of age

50

PIPERAZINE Only recommended for the treatment of

ascariasis. it is readily absorbed orally and excreted in urine Mechanism of action: it causes paralysis of ascaris by blocking

acetylcholine at myoneural junction ,expelling the live worm by normal peristalsis.

Not recommended for other helminth infections

51

Piperazine con’d

pharmacokinetics : it is readily absorbed orally and excreted

unchanged in urine.

75 mg /kg/day for 2 days once daily

treatment is continued for 3-4 days or repeated after one week in case of heavy infections.

52

Piperazine con’d

Adverse effects: GI disturbance Neurotoxicity ,allergic reactions serum sickness like

syndrome Contraindications Epilepsy Impaired liver or kidney functions pregnancy Malnutrition

53

Drugs used for treating human intestinal nematodes (single dose unless otherwise stated

Ascariasis Hookworm enterobius tricuris strongloides

Piperazzine ++ + ++ - -

Pyrantal pamoate ++ ++ ++ - -

Albendazole ++ ++ ++ + +

Mebendazole ++ ++ ++ + +

Thiabendazole n/a n/a n/a n/a ++

Ivermectin n/a n/a n/a n/a ++

54

NICLOSAMIDE

It is a useful drug for treatment of tape worm (cestodes)infestation

Mechanism of action: Adult worm is rapidly killed by inhibition of oxidative

phosphorylation or stimulation of ATPase activity. Pharmacokinetics: It is poorly absorbed from gut Neither drug nor its metabolites are found in blood or

urine

55

Niclosamide con’d

Clinical uses: T.Saginata( Beef tape worm),T.solium( pork tape

worm), Diphyllobothrium latum (fish tape worm) 2 gram of single dose is given in the morning on

the empty stomach. not effective against cysticercosis or hydatic

disease. Hymenolepis nana: It is effective against adult

parasite

56

Niclosamide con’d

Adverse effects: Mild ,infrequent and transitory GI

disturbance Alcohol consumption should be

avoided not indicated in children under 2

years of age.

57

DIETHYLCARBAMAZINE Is a drug of choice for the treatment of

filariasis ,loiasis and tropical eosinophillia. Pharmacokinetics: It is synthetic peprazine derivative Rapidly absorbed from gut It has a half life of 2-3 hours which increases in

alkaline urine to 10 hours. It is excreted in urine unchanged. dosage is reduced in urinary alkalosis and renal

impairment.

58

DIETHYLCARBAMAZINE con’d

Mechanism of action: It immobilizes microfilariae and alters its surface

structure ,making them susceptible to destruction by host defense mechanis

It is not teratogenic

59

DIETHYLCARBAMAZINE con’d It is a drug of choice for the treatment of W.bancrofti,

B.malayi,B.timori, loa loa

Microfiliariae are rapidly killed .adult worms are killed slowly requiring several course of treatment

It is highly effective against L.loa. for these infections the dose is 2mg/kg three times a day for 2-3 weeks.

for W.bancrofti infections to reduce the incidence of allergic reactions to dying microfilariae a single dose is administered on the first day , two doses on the second day and three doses on the 3rd day.

60

DIETHYLCARBAMAZINE con’d For loa ( with risk of encephalopathy) or B.malayi infections ,individual doses should start at 1 mg /kg once on the first day and gradually

increased over 5-6 days

Anti histamines and corticosteroids are given in allergic manifestations.

Complete Cure may be require several courses of treatment over 1-2 years.

The drug may be used in prohylaxis 300 mg weekly or 300 mg on 3 successive day each month for loiasis.

50 mg monthly for bancrofitan and malayan filariasis

Tropical eosinophilia 2 mg /kg tree time daily for 7 days

61

DIETHYLCARBAMAZINE con’d

Reactions induced by Dying parasites: Fever , mailase, papular rash, headache, GI

disturbance,cough, chest,muscle,joint pain Leucocytosis Retinal haemorrhage Encephalopathy lymphangitis and lymphadenopathy.

62

DIETHYLCARBAMAZINE con’d

contraindications and precautions

Hypertension

Renal disease

Patient suspected of malaria

patient with lymphangitis

63

IVERMECTIN

It is drug of choice for treatment of filaria and onchoceriais,elephantiasis

it is a macrocyclic lactone It is used orally and is rapidly absorbed, posses

wide volume of distribution. It has a half life of 16 hrs It is exclusively excreted in urine

64

IVERMECTIN con’d

Mechanism of action:64

it intensifies GABA –mediated transmission of singals in peripheral neverse

In onchoceriasis it is microfilaricidal It does not kill adult worm

65

IVERMECTIN con’d

Clinical uses: Onchoceriasis: a single dose of 150 mg/kg with

water on empty stomach,repeated after every 3 months for one year,after this it is repeated yearly untill adult worm dies which may take a year or more

66

IVERMECTIN con’d

Strongyloidiasis: 200mg for 2 days in immunosuppresed patient ,repeated treatment is often needed.

Bancrofti filaricidal: as it is mirofilaricidal It is also used for scabies and cutaneous larva

migrains.

67

IVERMECTIN con’d Adverse effects: Fatigue ,dizziness, GI disturbance In onchoceriasis: Mazotti reaction i.e. fever, headache, dizziness,

somonlence, weekness, rash ,diarrhea, arthralagia, hypotension, lymphadenitis, peripheral edema due to killing of microfiliariae, for this steroids may be necessary for several days

Swelling and abscess at site of adult worm Punctuate corneal opacities.

68

IVERMECTIN con’d

Contraindication: other drugs that enhance GABA

e.g Barbiturates, bnezodiazepines, valproaic acid. pregnancy Imparied blood brain barrier Children under 5 years of age.

69

BITHIONOL

it is drug of choice for the treatment of fasioliasis ( sheep liver fluke)

It is also alternative drug for pulmonary paragonimiasis

Pharmacokinetics: It is orally administered and excreted in urine.

70

BITHIONOL Clinical uses: 30-50 mg /kg in 2-3 divided doses administered orally

after meals on alternate day for 10 – 15 days. Adverse effects:

GI disturbanceDizziness,headachePruriuts ,urticaria,Leucopenia

Contraindications and precautions:hepatitis ,leucopeniaUsed with caution under 8 years of age.