DR.ABDUL LATIF MAHESAR
Department of Medical Pharmacology
Humans are the primary hosts for the most of
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
Worms live in hosts alimentary canal.
Worms or larvae live in other tissues of host
body like muscles , viscera , menninges ,
lungs, subcutaneous tissues.
INTESTINAL WORMS CON’D
A) INTESTINAL ROUND WORMS
Ascaris lmubricods (common round worm)
Enterobius vermicularis (pin worm)
Trichuris trichuria ( whip worm)
Strongyloids stercoralis ( thread worm)
Ankylostoma dudenale (hook worm)
Ascaris lumbricoids ( common round worm)
Pinworm male ,female
Tricuris tricura(whip worm)
1. Alimentary canal(intestinal tape worms)
B) TAPE WORMS (CESTODES)
Taenia saginata(Beaf) ,
Taenia solium(Pork),Hymenolepis nana(Dwarf)
Humans become infected by eating raw or
under cooked meat containing larvae of infected
cattle or pig which has encysted in the animal
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
2. TISSUE WORMS
(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
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
Paragonimus westermani (lung fluke)
disease is caused by eating raw crab or fish ,
larvae move from intestine to blood and settle in
Clonorchis sinensis(liver fluke)
disease is caused by eating raw fish and worm
settle in the biliary tract
Tissue worms cont’d
B. TISSUE ROUND WORMS
Dracunulus medinensis (guinea worm)larva
migrate from intestine to tissue of leg or foot and
protrude out by making ulcer
Wuchereria or Brugia obstructs lymphatic vessels
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
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.
Helminths commonly infecting man
Nematodes( round worm)
Intestinal human nematodes
Intestinal / hepatic flukes
Helminths commonly infecting man cont’d
Intestinal adult worms
Larval tissue cysts
Diseases caused by filarial worms
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,
Mechanism of action: It inhibits microtubule
synthesis in nematodes(intestinal round worms)
that irreversibly impairs glucose uptake,
intestinal parasites are immobilized and die
It is larvicidal in hydatid ,cysticercosis ,
ascariasis and hook worm infection.
Also ovicidal in ascariasis ,
ancyclostomiasis(hookworm) , tricurasis
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
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
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.
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
Other infections: Drug of choice in cutaneous and
visceral larvea migrans , intestinal cappillariasis
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
Not given during pregnancy and in hypersensitive
it is a synthetic benzimidazole
it has wider spectrum and is more safer than
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
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.
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
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
Adverse 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
enzyme inducers and inhibitors affect plasma level of the drug.
hepatic parenchymal disease
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
mechanism of action: similar to other benzimidazoles.It
is ovicidal for some paracites
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.
adverse reactions and contraindications:
It is more toxic than other benzamidazoles
Pruritus ,headache, drowsiness , psychoneurotic
Irreversible live failure.
Fatal Steven –Johnson syndrome(inflammation of skin)
Not used in children below 15 kg weight. pregnancy,
hepatic and renal diseases.
It is a broad specturm anthelmintic
but it is not effective against tricuriasis(whip worms), and
trichostrongylus orientalis infections. Oxalate pamoate is
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.
Pyrantel pamoate con’d
Efficacy and clinical uses:
it is very effective against luminal organisms.
It is not effective against migratory stages in the tissues or
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.
Pyrental pamoate con’d
Adverse Effects .
Infrequent mild transient GI disturbance
drowsiness , headache ,insomnia.
Should not be used in liver diseases.
and child under 2 years of age
Only recommended for the treatment of
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
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
Neurotoxicity ,allergic reactions serum sickness like
Impaired liver or kidney functions
Drugs used for treating human intestinal
nematodes (single dose unless otherwise stated
It is a useful drug for treatment of tape worm
Mechanism of action:
Adult worm is rapidly killed by inhibition of oxidative
phosphorylation or stimulation of ATPase activity.
It is poorly absorbed from gut
Neither drug nor its metabolites are found in blood or
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
Hymenolepis nana: It is effective against adult
Mild ,infrequent and transitory GI
Alcohol consumption should be
not indicated in children under 2
years of age.
Is a drug of choice for the treatment of filariasis
,loiasis and tropical eosinophillia.
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
Mechanism of action:
It immobilizes microfilariae and alters its surface
structure ,making them susceptible to destruction by
host defense mechanis
It is not teratogenic
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.
For loa ( with risk of encephalopathy) or B.malayi infections
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
Complete Cure may be require several courses of treatment over 1-2
The drug may be used in prohylaxis
300 mg weekly or 300 mg on 3 successive day each month for
Reactions induced by Dying parasites:
Fever , mailase, papular rash, headache, GI
disturbance,cough, chest,muscle,joint pain
lymphangitis and lymphadenopathy.
contraindications and precautions
Patient suspected of malaria
patient with lymphangitis
It is drug of choice for treatment of filaria and
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
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
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
Strongyloidiasis: 200mg for 2 days in
immunosuppresed patient ,repeated treatment is
Bancrofti filaricidal: as it is mirofilaricidal
It is also used for scabies and cutaneous larva
Fatigue ,dizziness, GI disturbance
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.
Contraindication: other drugs that enhance
e.g Barbiturates, bnezodiazepines, valproaic acid.
Imparied blood brain barrier
Children under 5 years of age.
it is drug of choice for the treatment of
fasioliasis ( sheep liver fluke)
It is also alternative drug for pulmonary
It is orally administered and excreted in urine.
30-50 mg /kg in 2-3 divided doses administered orally
after meals on alternate day for 10 – 15 days.
Contraindications and precautions:
Used with caution under 8 years of age.