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Parasitic Worm Drugs
1. Dr. RAGHU PRASADA M S
MBBS,MD
ASSISTANT PROFESSOR
DEPT. OF PHARMACOLOGY
SSIMS & RC.
1
2. Drugs used to treat parasitic worm infections
Unlike protozoa, helminths are large and have complex
cellular structures
Drug treatment is very specific
It is very important to identify the causative worm
Done by finding the parasite ova or larvae in
faeces, urine, blood, sputum, or tissue
VERMICIDAL or VERMIFUGE drugs
5. Benzimidazoles(Albendazole & Mebendazole )binds
to beta tubulin prevents polymerisation
break down of cytoplasmic microtubules
they Inhibit uptake of glucose and other nutrients
depletion of glycogen stores
decrease of ATP
leading to autolysis and death of the parasitic worm
Mebendazole is absorbed after oral – 10%
Fatty meal increases absorption Albendazole,
mebendazole
6. It is rapidly metabolised, the products being excreted
in the urine and the bile within 24-48 hours.
Single dose for threadworm,
BD daily for 3 days for hookworm and roundworm
infestations.
Thiabendazole is rapidly absorbed orally
Albendazole is metabolised extensively by first-pass
metabolism to the sulfoxide so has t1/2 -8-10 hrs
7. It is effective in infections with the common round-worm as well
as hook worm
MOA: It has a nicotine-like action, stimulating and subsequently
blocking the neuromuscular junctions. The paralyzed worms
are then expelled in the faeces. Ova are not killed.
Phamacokinetics:
The drug is given orally, is rapidly absorbed and is widely
distributed. It crosses the blood-brain barrier.
Side effects: They include gastrointestinal disturbances,
Dizziness and skin eruptions. High concentrations can have
nicotinic actions on autonomic ganglia in the mammalian
host. There are some reports of encephalopathy
8. It is highly effective broad-spectrum antiparasitic
First choice of drug for the treatment of filarial infections
and is very effective in onchocerciasis
MOA:
It kill the worm by opening glutamate-gated chloride
channels (found only in invertebrates) and increasing Cl-
conductance; by binding to a novel allosteric site on the
acetylcholine nicotinic receptor to cause an increase in
transmission, leading to motor paralysis; or by binding to
aminobutyric acid receptors.
9. Uses :
It has given good results against W. bancrofti, which
causes elephantiasis.
A single dose kills the immature microfilariae of O.
volvulus- river blindness
The drug also has activity against common
roundworms, whipworms, and threadworms
Side effect: skin rashes, fever, giddiness, headaches
and pains in muscles, joints and lymph glands
10. Diethylcarbamazine is a piperazine derivative
It is active in filarial infections caused by W. bancrofti
It mainly act by make opsonisation of worm that detected by
our immune system alters microfilarial membrane
surface characters It hyperpolarises worm
musculature phagocytosed by tissue fixed monocytes
expelled from body
The drug is absorbed by oral administration and clear from
body within 48 hrs
Side effects
Gastrointestinal disturbances, arthralgias, headache and a
general feeling of weakness
11. MOA:
Its action has been ascribed to inhibition of the parasite's
mitochondrial anaerobic phosphorylation of ADP which
produces usable energy
The scolex and a proximal segment are irreversibly damaged
by the drug
The worm separates from the intestinal wall and is expelled
There is negligible absorption of the drug from the
gastrointestinal tract.
Taenia solium, the drug is given in a single dose after a light
meal, followed by a purgative 2 hours
Unwanted effects are few, infrequent and transient. Nausea
and vomiting can occur.
12. Adverse effects
Drowsiness, dizziness, Malaise,
anorexia, as well as gastrointestinal upsets.
It is contradicted in pregnant women or nursing mothers.
Drug interaction:
Enzyme inducers dexamethasone, phenytoin, and
carbamazepine increase metabolism
Cimetidine, known to inhibit cytochrome P-450 isozymes,
causes increased praziquantel levels.
13. It is the drug of choice for all forms of schistos and for
cestode infections like cysticercosis.
MOA:
paralyses both adult worms and Larvae.
It causes influx of Ca+ vacuolation and exposure of
antigens phagocytosis
Permeability of the cell membrane to calcium is
increased, causing contracture and paralysis of the
parasite.
Pharmacokinetics:
It is rapidly absorbed after oral administration and
distributes into the cerebrospinal fluid.
14. Thiabendazole inhibits cellular enzymes
of susceptible helminths. Inhibits the helminth-specific
enzyme, fumarate reductase
Piperazine-It reversibly inhibits neuromuscular
transmission in the worm
It probably acts on GABA/GABA-gated chloride
channels in nematode muscle. The paralyzed worms
are expelled alive
Pyrantel pamoate- blocks acetylcholine at the
neuromuscular junction, resulting in paralysis of the
worms, which are then expelled through the GI tract
16. Worms (helminths) Drug of choice
Tapeworms (cestodes) Niclosamide or Praziquantel or
Albendazole
Roundworms (nematodes)
•Enterobius vermicularis (pinworm)
•Ascaris lumbricoides
•Trichuris trichiura (whipworm)
•Trichinella spiralis (trichinellosis)
•Strongyloides stercoralis
•Necator americanus (hookworm)
•Ancylostoma duodenale
•Onchocerca volvulus (Onchocercosis)
•Wuchereria bancrofti (Elephantiasis)
Mebendazole or Pyrantel
Mebendazole or Pyrantel
Mebendazole or Albendazole
Mebendazole
and Thiabendazole
Thiabendazole
Mebendazole or Pyrantel
Mebendazole, Pyrantel, or
Albendazole
Ivermectin
Diethylcarbamazine
Flukes (trematodes)
•Schistzoma (Schistozomes) Praziquantel
17. Metrifonate:
It is safe and cost effective for schistosoma
infection
It is cholinesterase inhibitors
Orally active and t1/2 =1-5 hrs
Oxaminiquine:
It is the drug of choice for all forms of
schistosomiasis
It intercalated with parasite DNA and inactivate it
Bithionol
Triclabendazole
