UNIT 2: ANTHELMINTIC (ANTIHELMINTHIC) DRUGS
Key Unit Competence
Utilize appropriate anti-helminthic
drugs to manage different
health conditions
at the primary healthcare settings.Introductory activity 2.0
1) What do you observe on the image above?
2) Have you ever seen the same
scenario in your community?
If yes, which drugs have you seen
being used in the same scenario?
2.1. Introduction to anthelmintic
drugs and deworming
Learning Activity 2.1
Read the scenario below:
A patient GN presents at your
health clinic with
the complaints of severe
abdominal pain, vomiting
and diarrheas'.
For all physical examination
performed,
no signs of abnormalities found.
All vital signs
are normal and by history taking,
his family lives in a region
with poor sanitation.
The laboratory results revealed
the presence of eggs of Ascaris during
the direct stool examination.
In addition, the patient tells you that
he was given one year ago thedrug as a single dose, the treatment which was given in mass campaign.
1) What is the disease do you think
patient GN
is suffering from?
2) Which of the following
medications may be
used in mass deworming?
a) Tinidazole
b) Mebendazole
c) Metronidazole
d) Amoxicillin
3) What are the classes of helminthic
parasites are oftentargeted in deworming?
CONTENT SUMMARY
Helminths are a broad range of
organisms that include
intestinal parasitic worms.
There are three major groups
of helminths namely:
nematodes (roundworms),
trematodes (flukes) and
cestodes (tapeworms).
These groups of helminths are
divided into two phyla;
nematodes (roundworms)
and platyhelminths
(trematodes and cestodes).
Infected people excrete helminth
eggs in their faeces,
which then contaminate the s
oil in areas with inadequate sanitation.
Other people can then be infected
by ingesting eggs or
larvae in contaminated food,
or through penetration
of the skin by infective
larvae in the soil (hookworms).
Infestation can cause morbidity,
and sometimes
death, by compromising
nutritional status,
affecting cognitive processes,
inducing tissue
reactions, such as granuloma,
and provoking
intestinal obstruction or
rectal prolapse.
Control of helminthiasis
is based on drug
treatment,
improved sanitation and
health education.
Over millions of preschool-age children and
school-age children live in areas where these
parasites are intensively transmitted,
and are in need of treatment and preventive
interventions.
Anthelminthics are a group of antiparasitic
drugs that expel parasitic worms
(helminths) and other internal parasites
from the body by either stunning or
killing them and without causing significant
damage to the host. They may also
be called vermifuges (those that stun) or
vermicides (those that kill). Anthelmintics
are used to treat people who are infected
by helminths, a condition called helminthiasis.
Pills containing anthelmintics are used in mass
deworming campaigns of school
aged children in many developing countries.
Anthelmintic are classified based
upon their chemical structures.
i. Piperazines: eg. Diethylcarbamazine
citrate, Piperazine citrate.
ii. Benzimidazoles: eg. Albendazole,Mebendazole, Thiabendazole.
Albendazole Use:
It is a new benzimidazole useful in the
treatment of intestinal nematode infection
and echinococcosis. It is effective against
roundworm, hookworm, whipworm
and threadworm infestations.It is effective in the treatment of ascariasis.
Mebendazole Use:
It is used in the treatment of hookworm,
pinworm, and roundworm andwhipworm infestation.
iii. Heterocyclics: eg. Oxamniquine,
Praziquantel. Praziquantel
Use: It is considered as drug of choice for
the treatment of Schistosoma japonicum,
(blood fluke) falciolopsiasis (intestinal flukes)
clonorchiasis (chinese liver fluke) andopisthorchosis (liver fluke)
iv. Natural products:
eg. Ivermectin, Avermectin.
Use: Ivermectin is widely used
in veterinary practice
for the control of endoparasite
and exoparasite in domestic animals.
It is also used to treat onchocerciasis in humans. caused by round worm
Onchocerca volvulus.
v. Vinyl pyrimidines :
eg. Pyrantel, Oxantel. Pyrantel
Use: The anthelmintic choice in the treatment
of hookworm, pinworm and roundworm Infestations.
vi. Amide:
eg. Niclosamide (Niclosan)
Use: The anthelmintic of first choice in the
treatment of beef tapeworm, fish tapeworm,
pork tapeworm and dwarf tapeworm infestations.
vii. Nitro derivative: eg. Niridazole.
viii. Imidazo thiazole: eg. Levamisole
Deworming is the giving of an anthelmintic
drug to a human to rid them
of helminths parasites, such as roundworm,
flukes and tapeworm.
Mass deworming campaigns of school children
have been used both
as a preventive as well as a treatment method
for helminthiasis, which
includes soil transmitted helminthiasis
in children. Children can
be treated by administering, for example,
mebendazole and albendazole.
According to the World Health Organization
(WHO), over 870 million children
(half of the children in the world)
are at risk of parasitic worm infection.
Worm infections interfere with nutrient
uptake, can lead to anemia,
malnourishment and impaired mental
and physical development,
and pose a serious threat to children’s health,
education, and productivity.
Infected children are often too sick or
tired to concentrate at school, or to attend at all.
Self-assessment 2.1
1) Give the classes of anthelminthic drugs.
2) The deworming of children usually involves
the use of mebendazole and coartem. True or False
3) Worm infections interfere with nutrient uptake,
and can lead to anemia. True or False
2.2. Anthelmintic medications
Learning Activity 2.2
A patient X was admitted in a clinical health
facility for intestinal worm infestation.
After the laboratory investigations done,
they found the eggs of hookworm in the stool.
The healthcare providers decide to prescribe
a drug that would be effective
to manage the client’s condition.
1) Which class of drugs can be used
to manage the client’s condition?
2) What is the mechanism of action
of mebendazole?
3) What are the common sideeffects of albendazole?
CONTENT SUMMARY
Anthelmintic agents are indicated for the
treatment of infections by certain susceptible
worms and are very specific in the worms that
they affect; they are not interchangeable
for treating various worm infections.
Treatment of a helminthic infection
entails the use of an anthelmintic drug.
Another important part of therapy for
helminthic infections involves
the prevention of reinfection or spread
of an existing infection.
Measures such as thorough
hand washing after use of the toilet;
frequent laundering of bed linens
and underwear in very hot,
chlorine-treated water; disinfection
of toilets and bathroom areas
after each use; and good
personal hygiene to wash away
ova are important to preventthe spread of the disease.
When the infestation is present or associated
with complications occur, pharmacotherapy
is initiated. Pharmacotherapy is targeted at killing the
parasites locally in the intestine and systemically inthe tissues and organs they have invaded.
Table Common anti-helminthic drugs
Mebendazole (Vermox)
Mechanism of action Mebendazole is
the most widely prescribed anthelmintic.
Mebendazole is available in the form of
a chewable tablet, and a typical 3-day course
can be repeated in 3 weeks if needed.
Mebendazole interferes with the ability to use
glucose, leading to an inability to reproduce
and cell death. It is used in the treatmentof a wide range of helminth infections,
including those caused by roundworm (Ascaris)and
pinworm (Enterobiasis). As a broadspectrum drug,
it is particularly valuable in mixed
helminth infections, which is more common
in regions with poor sanitation. It is effective
against both the adult and larval stages
of these parasites. Because very little
of mebendazole is absorbed systemically,
it retains high
concentrations in the intestine where
it kills the pathogens.
For pinworm infections, a single
dose is usually sufficient;
other infections require 3 consecutive
days of therapy.
Pharmacokinetics
Very little of the mebendazole
is absorbed systemically,
so adverse effects are few.
The drug is not metabolized in the body,
and most of it is excretedunchanged in the feces.
A small amount may be excreted in the urine.
Administration Alerts
– The drug is most effective when chewed
and taken with a fatty meal.
– Pregnancy category
C. Adverse Effects: Because so little
of the drug is absorbed, mebendazole does not
generally cause serious systemic side effects.
As the worms die, some abdominall pain, distention, and diarrhea may be experienced.
Contraindications:
The only contraindication is
hypersensitivity to the drug.
Interactions:
Drug–Drug: Carbamazepine and
phenytoin can increase the metabolism
of mebendazole.
Lab Tests: Unknown interaction with lab tests.
Herbal/Food: High-fat foods may increase
the absorption of the drug. Treatment of Overdose:
There is no specific treatment for overdose.
Albendazole
Albendazole is an anthelmintic
or anti-worm medication.
It prevents newly hatched insect larvae
(worms) from growing or multiplying in the body.
Mechanism of action
As a vermicide, albendazole causes
degenerative alterations in the intestinal cells
of the worm by binding to the colchicine
-sensitive site of β-tubulin,
thus inhibiting its polymerization or
assembly into microtubules
(it binds much better to the β-tubulin
of parasites than that of mammals)
Albendazole leads to impaired uptake
of glucose by the larval and adult
stages of the susceptible parasites,
and depletes their glycogen stores.
Albendazole also prevents the formation
of spindle fibers needed for
cell division, which in turn blocks egg
production and development;existing eggs are prevented from hatching.
Pharmacokinetics
Oral absorption of albendazole varies among
species, with 1–5% of the drug being successfully
absorbed in humans, 20–30% in rats, and 50% in cattle.
The absorption also largely depends on gastric pH.
People have varying gastric
pHs on empty stomachs, and
thus absorption from one person
to another can
vary wildly when taken without food.
Generally, the absorption in the GI tract is
poor due to albendazole’s low solubility in water.
It is, however, better absorbed
than other benzimidazole carbamates.
Food stimulates gastric acid secretion,lowering the pH and making albendazole
more soluble and thus more easily absorbed.
Oral absorption is especially increased with a fatty meal,
as albendazole dissolves better
in lipids, allowing it to cross the lipid barrier created
by the mucus surface of the GI tract.
To target intestinal parasites, albendazole
is taken on an empty stomach to stay
within the gut. Absorption is also affected
by how much of the albendazoleis degraded within the small intestine
by metabolic enzymes in the villi.
The pharmacokinetics of albendazole differ
slightly between men and women:
women have a lower oral clearance
and volume of distribution, while men havea lower serum peak concentration
Common side effects
The most common side effects by albendazole
are experienced by over 10%
of people and include: Headache, neck stiffness,
increased sensitivity to light,
confusion; fever; nausea, vomiting, stomach pain;
abnormal liver function tests;
dizziness, spinning sensation;
or temporary hair loss.
Ivermectin (Stromectol)
Stromectol is a prescription medicine used
to treat the symptoms of
certainparasiteinfections (Strongyloidiasis
of the Intestinal Tract and River BlindNess
[Onchocerciasis]). Stromectol may be used
alone or with other medications.
Mechanism of action
Ivermectin is an anti-parasitic medication.
Ivermectin works by binding to
invertebrate muscle and nerve
cells of parasites,
causing paralysis and death of
parasites. Ivermectin is active against
the non-adult form of Onchocerca volvulus.
Pharmacokinetics
Ivermectin is readily absorbed from the GI
tract and reaches peak plasma levels
in 4 hours. It is completely metabolized
in the liver with a half-life of 16 hours;excretion is through the feces.
Indications
STROMECTOL (ivermectin) is indicated for the
treatment of the following infections:
Strongyloidiasis of the intestinal tract.
Stromectol
(ivermectin) is indicated for the
treatment of intestinal (i.e., nondisseminated)
strongyloidiasis due to the nematode
parasite Strongyloides stercoralis.
Is indicated for the treatment of onchocerciasisdue to the nematode parasite Onchocerca volvulus.
Doses
The recommended dosage of STROMECTOL
for the treatment of onchocerciasis
is a single oral dose designed to provide
approximately 150 mcg of ivermectin perkg of body weight. Patients should take
tablets on an empty stomach with water.
Side effects
The most common side effects of Stromectol
include: Headache, muscle aches,
dizziness, nausea, diarrhea, and mild skin rash
Contraindications / Precautions
It contraindicated in Asthma, Hepatic disease,
Human immunodeficiency virus(HIV) infection, immunosuppression,
Pregnancy, Breast-feeding, Children, infants.
Praziquantel
Praziquantel is used to treat infections
caused by Schistosoma worms
Mechanism of action
The action of praziquantel is limited very
specifically to trematodes and cestodes;
nematodes (including filariae) are not affected.
Praziquantel works by causing
severe spasms and paralysis
of the worms’ muscles.
This paralysis is accompanied- and probably caused
- by a rapid Ca 2+ influx inside the schistosome
Pharmacokinetics
The absorption of praziquantel is rapid
and nearly complete but the systemic
bioavailability of praziquantel is low and
varies considerably between individuals.
After the administration of 40 mg/kg to fasted
healthy adults Oral drugs have a
greater pharmacokinetic variability than drugs
administered by the intravenous
route, explained by the blood flow at the
absorption site, the absorptive surfacearea, the transit time and the gastric pH,
factors all influenced by concurrent food uptake
Dosages of Praziquantel:
Adult and Pediatric Dosages:Dosage Considerations
– Should be Given as Follows:
Adult Dosage:
20 mg/kg orally three times per day for 1 day, every 4-6 hours
Pediatric Dosage:
Children under 4 years old:
safety and efficacy not established
Children 4 years and older:
20 mg/kg orally three times daily for 1 day,
every 4-6 hoursContraindication
BILTRICIDE (praziquantel) is contraindicated
in patients who previously have shown
hypersensitivity to the drug or
any of the excipients.
Since parasite destruction
within the eye may cause
irreversible lesions,
ocular cysticercosis must not betreated with this compound.
Side effects
Abdominal pain, allergic reaction,
cerebrospinal reaction syndrome, diarrhea,
dizziness, drowsiness, feeling unwell
(malaise), fever, headache, hives, itching,
mild fever, mild skin rash, nausea, rash,
sweating, tired feeling, upset stomach,vomiting.
Self-assessment 2.2
1) Which of the following drugs
can be used in the treatment of schistosoma
infection?
a) Praziquantel
b) Ivermectin
c) Albendazole
d) Mebendazole
2) What is the mechanism of action of albendazole?
3) As a nurse student in the clinical placement,
you are providing health
education to a patient who is taking albendazole.
Which of the following
statements should be included in your teaching?
a) Oral absorption is especially decreased
with a fatty meal, and it should
not never be taken with fatty meal
b) Albendazole dissolves better in water,
and drinking a lot of water speeds
up its absorption
c) Albendazole can never cross the
lipid barrier created by the mucus
surface of the GI tract.
d) To target intestinal parasites,
albendazole is taken on an empty stomachto stay within the gut.
2.3. National Guidelines for Deworming and
WHO Community Deworming
Learning Activity 2.3
1) Which activity does the image above indicate?
2) Which medications and at which doses does
the WHO recommend for
deworming using annual or biannual
single-dose as a public health
intervention for children aged 7 years old?
3) Deworming of children and
pregnant women and children through the
health services and in schools is well
established and can help to reduceiron deficiency. True or False
CONTENT SUMMARY
Those living in poverty are most vulnerable to
infection which can impair nutritional
status by causing internal bleeding which
can lead to loss of iron and anemia;
intestinal inflammation and obstruction;
diarrhea; and impairment of nutrient intake,digestion and absorption.
Evidence shows that preventive chemotherapy,
or the periodic large-scale
administration of anthelminthic medicines
to populations at risk, can dramaticallyreduce the burden of worms caused by
soil-transmitted helminth infections.
Preventive chemotherapy is an important
\ part of a comprehensive package to
eliminate morbidity due to soil-transmitted
helminths in at-risk populations. However,
long-term solutions to soil-transmitted helminth
infections will need to address many
factors, including improvements in water,sanitation and hygiene.
The WHO recommends Preventive chemotherapy
(deworming), using annual or
biannual single-dose albendazole (400 mg)
or mebendazole (500 mg) as a public
health intervention for all young children
12–23 months of age, preschool children1–4 years of age, and school-age children
5–12 years of age living in areas where
the baseline prevalence of any soil-transmitted
infection is 20% or more amongchildren, in order to reduce the worm burden
of soil-transmitted helminth infection.]
Self-assessment 2.3
1) What is the important part of a
comprehensive package to eliminate
morbidity due to soil-transmitted helminths
in at-risk populations?2) Discuss on how deworming is
being applied in your community?
2.4. End unit assessment
End of unit assessment
1) What are the three major groups
of helminths?
2) Which of the following can be
classified in heterocyclics ?
a) Piperazine citrate.
b) Thiabendazole
c) Mebendazole
d) Praziquantel
3) Ivermectin is classified among natural
products category of anthelminthic
drugs. True or False.
4) Which of the following are
the most commonly used medications in
deworming?
a) Mebendazole and albendazole
b) Mebendazole and tinidazole
c) Mebendazole and Ivermictin
d) Ivermictin and albendazole
5) Due to its effectiveness,
praziquantel is the drug of choice for filariae.
True or False
6) The deworming is the giving
of an anthelmintic drugs human to help them
get rid of:
a) Roundworms, flukes and protozoa
b) Roundworms, flukes and tapeworm
c) Flukes, protozoa and tapewormd) Protozoa, tapeworm and roundworms