Antihelminthics

Question 1

What are antihelminthics?

Answer 1

drugs used for controlling the parasitic worms or helminths that inhabit the organs and tissues of animals:

• GIT (ascarids, tapeworm, flukes)
• respiratory system (Dictyocaulus)
• heart-worm (Dirofilaria)
• muscle (trichinella) and connective tissue

Question 2

An ideal antihelminthic would have the following 7 properties:

Answer 2

1) A wide therapeutic index (1:6 and more)
2) A broad spectrum of activity against all those classes of parasites that are pathogenic, zoonotic and of an economic importance. Some modern anthelmintics are effective against nematodes, trematodes, cestodes and even against acathocephalic parasites.
3) Efficacy against migrating and hypobiotic (arrested) larvae of nematodes, immature flukes and scolexes of cestodes as well against adult worms.
4) A short residence time in the milk or tissue in case of treating of food animals, i. e. a short withdrawal period. In non-foodstuffs animals, prolonged presence of drug can be advantageous by providing an extended protection against the reinfection.
5) No unpleasant side-effects or hazards to the animal.
6) It should be compatible with other therapeutic agents (interactions), easy to be administered and stable (i. e. not decomposed by light, temperature, moisture etc.) and does not require repeated administrations.
7) Economic aspects. Low price of drug (treatment should be significantly cheaper than price of animal esp. in decorative pets).

Question 3

Describe wide therapeutic index in terms of antihelminthics

Answer 3

A wide therapeutic index (1:6 and more). It is a ratio of therapeutic dose to the maximum tolerated dose. A therapeutic index of 1:2 is very narrow, indicating that twice the dose required to destroy the parasite will be toxic to the host. A safety
margin of at least six-fold is expected of modern anthelmintics.

Question 4

Describe the basic principles of antihelminthic treatment

Answer 4

1) First to identify the parasitic infection (nematode, cestode etc.)
2) To select an appropriate drug to treat this condition in regard to species of parasite, but also to animal, for example, food animal, animals in lactation, pregnancy (teratogenicity), exhausted animals, high body temperature, extent of infestation by helminths.
3) To determinate the dose of drugs (higher dosage against immature forms)
4) The choice of the best way of administration
5) The time of treatment, for example in calves antinematodal drugs are recommended in midsummer, when pastural larval infestations reach their peak.
6) Repeated administrations should be done according to the protection properties of used anthelmintics or according to the possibility of reinfection in grazing animals (for example ivermectin activity persists for several weeks after dosing). Modern technology has produced single-dose boluses which reside in the rumen after dosing and offer protection of animals over the entire grazing period.

Question 5

When is repeated administration absolutely necessary?

Answer 5

in the case of drugs without activity against immature forms of parasites (piperazine).

Question 6

How can antihelminthics be administered?

Answer 6

1. Anthelmintics of very low toxicity are administered in diet (benzimidazoles) or in drinking water. They must be stable in water.
2. Orally as a drench (sheep), tablets, boluses, pills, granules by esophageal tube in individual animals, what provides an exact dosage of the drug.
3. Parenterally ex. levamisole and ivermectin.

Question 7

Describe the 4 mechanisms of action of antihelminthics

Answer 7

1. inhibitors of tubulin polymerization - benzimidazoles and probenzimidazoles (which are metabolized in vivo to active benzimidazoles and thus act in the same manner)
2. uncouplers of oxidative phosphorylation - salicylanilides and substituted phenols
3. inhibitors of enzymes in the glycolytic pathway – clorsulon
4. interfere with neuromuscular apparatus (cholinomimetic effect, increasing of GABA release,..) – organophosphates, macrocyclic lactones

Question 8

Resistance of Haemonchus contortus and Nematodirus spp.

Answer 8

The frequency of anthelmintic treatment in sheep, as for example in Australia against Haemonchus contortus (monthly) is ideally suited to the development of resistance. Benzimidazole resistance is in direct relationship to the frequency of dosing.

Resistance of H. contortus and Nematodirus spp. against thiabendazole was detected already only 3 years after this product was introduced to the therapy. Later it was found that cross-resistance was developed between thiabendazole and its newer derivatives.

Question 9

How to prevent resistance?

Answer 9

Sensible application of modern anthelmintics (ivermectin, albendazole etc.) provides an opportunity to control the resistance problem.
Therefore, the best way to prevent the development of worm resistance is to minimize the frequency of dosing, to alternate the treatment between different classes of anthelmintics or take advantage of the prophylaxis offered by slow-release rumen boluses and especially to make full use of clean pasture.

Question 10

Which factors predispose the development of drug resistance?

Answer 10

• using anthelmintics below their recommended dose,
• continued use of a single type of anthelmintic, or
• excessive treatment of animals.

Question 11

Briefly describe the pharmacokinetics of antihelminthics

Answer 11

Although many helminth parasites reside in the lumen or close to the mucosa, others live at sites such as the liver and lungs; for action against these, absorption of drug from the GI tract, injection site, or skin is essential.

After administration, anthelmintics are usually absorbed into the bloodstream and transported to different parts of the body, including the liver which is the usual site of metabolism of anthelmintics - oxidation and cleavage reactions commonly occur. They are then eventually excreted in the faeces and urine.

Question 12

Describe the division of antihelminthics

Answer 12

1. / Antinematodics - antiparasitics against roundworms: Trichostrongylus, Haemonchus, Ascaris, Nematodirus, Strongylus, etc.
2. / Antitrematodics - antiparasitics effective against flukes from genera: Fasciola, Paramphistomum, Paragonimus, Dicrocoelium, Opisthorchis
3. / Anticestodics - antiparasitics against tapeworms: Taenia, Echinococcus, Dipilidium, Moniezia, etc.
4. / Antiacanthocephalics

Question 13

Describe the division of antinematodal drugs according to their chemical structure and list the active substances

Answer 13

1) Imidazoles
a) benzimidazoles (thiabendazole and its derivatives, albendazole, fenbendazole, flubendazole mebendazole, oxfendazole, oxibendazole, parbendazole),
b) probenzimidazoles (febantel, netobimin),
c) imidazothiazoles (levamisole, tetramisole)
2) Macrocyclic lactones (avermectins, milbemycins),
3) Tetrahydropyrimidines (pyrantel, morantel, oxantel and others),
4) Organophosphorous compounds (dichlorvos, haloxon, trichlorfon, coumaphos, etc.),
5) Heterocyclic compounds (piperazine, diethylcarbamazine, phenothiazine),
6) Miscellaneous nematocidal compounds (emodepsid, nitroscanate)

Question 14

Name the 3 subgroups of imidazoles

Answer 14

Benzimidazoles, probenzimidazoles, imidazothiazoles

Question 15

Name the active substances of benzimidazoles

Answer 15

thiabendazole and its derivatives, albendazole, fenbendazole, flubendazole mebendazole, oxfendazole, oxibendazole, parbendazole

Question 16

What was the first benzimidazole introduced to therapy?

Answer 16

Thiabendazole

Question 17

Use of benzimidazoles and their safety

Answer 17

The benzimidazoles are a large chemical family used to treat nematode and trematode infections in domestic animals. They also have limited activity against cestodes.
With few exception benzimidazoles are very safe anthelmintics having a high therapeutic index, but care needs when administered in pregnant animals (embryotoxicity and teratogenicity).

Question 18

Disadvantage of benzimidazoles

Answer 18

development of resistance (thiabendazole within 3 years) and also cros-sresistance to other benzimidazoles, when used in frequent intervals throughout the year.

Question 19

Absorption of benzimidazoles

Answer 19

With a few exceptions, eg, albendazole, oxfendazole, only limited amounts of any of the benzimidazoles are absorbed from the GI tract of the host. The limited absorption is probably related to the poor water solubility of these drugs.
The little absorption that occurs is generally rapid.

Question 20

How do benzimidazoles reenetr the GIT after being absorbed?

Answer 20

Many of the benzimidazoles and their metabolites re-enter the GI tract by passive diffusion, but the biliary route is the most important pathway for secretion and recycling of benzimidazoles to the GI tract.

Question 21

Which spp. are benzimidazoles most effective in?

Answer 21

Benzimidazoles are more effective in ruminants and horses, in which their rate of passage is slowed by the rumen or cecum. The rumen acts as a drug reservoir from which plasma concentrations can be sustained, slowing the passage of unabsorbed drug through the GI tract.

Question 22

Benzimidazole mechanism of action

Answer 22

act primarily by binding to nematode β- tubulin. It prevents its dimerization with α-tubulin and polymerization of tubulin oligomers into microtubules.
Microtubules are essential structural units of many organelles and are necessary for numerous cellular processes, including mitosis, protein assembly, and energy metabolism.

Question 23

Describe thiabendazole

Answer 23

Thiabendazole is the first of this generation still used against adult and larval nematodes.

Question 24

Describe albendazole

Answer 24

Activity: It is effective against important nematodes and their larvae including hypobiotic or inhibited forms and also against cestodes, and some flukes.
Use: Widely for treating ruminant roundworms and flukes in the form of intraruminal bolus.

Question 25

Albendazole dose

Answer 25

5-7.5 mg/kg

Question 26

Describe fenbendazole

Answer 26

It is active against all important nematodes including the inhibited larvae and also against some tapeworms.

Question 27

Describe flubendazole

Answer 27

Flubendazol is used for treating round worms only in pigs

Question 28

Describe mebendazole

Answer 28

Mebendazole is effective against roundworms, tapeworms and also cestode's larvae, it is not generally used in cattle.

Question 29

Describe oxfendazole

Answer 29

It is effective against nematodes and their inhibited larvae and cestodes. Oxfendazole is a sulphoxide metabolite of fenbendazole & is probably responsible for the activity of both these anthelmintics. This means that fenbendazole is metabolized to oxfendazole.

Question 30

Describe oxibendazole

Answer 30

Against GI and lung worms (nematodes) it is usually employed in horses

Question 31

Describe parbendazole

Answer 31

It was a first derivate of thiabendazole, but is less widely used today. It is effective against most GI nematodes and lungworms.

Question 32

Name the active substances of imidazothiazoles

Answer 32

Levamisole, tetramisole

Question 33

What is levamisole?

Answer 33

Levamisole is the l-isomer of tetramisole. It is a water soluble substance, which may be administered orally and parenterally

Question 34

Levamisole mechanism of action.

Answer 34

Levamizole as a cholinergic agent causes paralysis of worms but also inhibits the enzyme fumarate reductase.

Question 35

Levamisole use

Answer 35

is effective against adult and larval GI roundworms and lungworms. It has a rapid effect on parasites, expelling most worms within 24 h. It is important for treatment the benzimidazole-resistant worms. It has also garnered much interest as an immunostimulant in the adjunctive therapy of various neoplasms.

Question 36

Name the active substances of probenzimidazoles

Answer 36

Febantel and Netobimin

Question 37

What are probenzimidazoles?

Answer 37

Two probenzimidazole compounds, febantel and netobimin, exist in the form of pro-drugs and must be metabolized in the GI tract to the biologically active benzimidazole carbamate nucleus.

Question 38

Describe febantel

Answer 38

It is a precursor of fenbendazol so its activity is the same of that of fenbendazol

Question 39

Describe netobimin

Answer 39

It is a precursor of albendazol.

Question 40

Define and describe macrocyclic lactones

Answer 40

macrocyclic lactones (avermectins and milbemycins) are products or chemical derivatives of soil microorganisms belonging to the genus Streptomyces. They have a potent, broad antiparasitic spectrum at low dose levels.

Question 41

Use of macrocyclic lactones

Answer 41

They are active against many immature nematodes (including hypobiotic larvae) and arthropods (ectoparasites). Are NOT effective against cestodes and trematodes.

Question 42

Describe absorption and distribution of macrocyclic lactones

Answer 42

Are well absorbed when administered PO or parenterally. Regardless of the route of administration, macrocyclic lactones are extensively distributed throughout the body and concentrate particularly in adipose tissue. Effective levels are reached in the GI system, lungs, and skin. The association of macrocyclic lactones with digesta affects absorption. Liver tissue contains the highest residue for the longest time, reflecting the route of elimination. Although the magnitude of lipophilicity differs among chemical types, the limited vascularization and slow turnover rate of body fat and the slow rate of release or exchange of drug from these lipid reserves can prolong the residence of drug in the peripheral plasma.

Question 43

Describe avermectins

Answer 43

Since the discovery of benzimidazoles, avermectins represent the biggest breakthrough in parasite control. Macrolide endectocides avermectins and closely related milbemycins are produced by actinomycete micro-organisms Streptomyces avermitilis. They are highly potent with wide spectrum activity against nematodes and ectoparasitic arthropods, require very small doses, with long persisting activity and may be administered orally or parenterally with acceptable safety margin, without embryotoxicity and teratogenicity.

Question 44

Name the avermectins

Answer 44

Ivermectin, Doramectin, Selamectin, Eprinomectin

Question 45

Use of ivermectin

Answer 45

Ivermectin is approved in horses for the control of large strongyles (adult), small strongyles, pinworms, ascarids, hairworms, large-mouth stomach worms, neck threadworms (microfilaria), bots, lungworms, intestinal threadworms, and summer sores secondary to Hebronema or Draschia spp. In cattle, ivermectin is approved for use in the control of gastrointestinal roundworms, lungworms, cattle grubs, sucking lice, and mites (scabies). In swine, ivermectin is approved for use to treat GI roundworms, lungworms, lice, and mange mites. In reindeer, ivermectin is approved for use in the control of warbles. In dogs and cats, ivermectin is approved for use as a preventative for heartworm. It has also been used as a microfilaricide, slow-kill adulticide, ectoparasiticide, and endoparasiticide.

Question 46

Ivermectin mechanism of action

Answer 46

Ivermectin enhances the release of gamma amino butyric acid (GABA) at presynaptic neurons. GABA acts as an inhibitory neurotransmitter and blocks the post- synaptic stimulation of the adjacent neuron in nematodes, or the muscle fiber in arthropods. By stimulating the release of GABA, ivermectin causes paralysis of the parasite and eventual death. As liver flukes and tapeworms do not use GABA as a peripheral nerve transmitter, ivermectin is ineffective against these parasites.

Question 47

When NOT to use ivermectin

Answer 47

ivermectin should not be used in breeds susceptible (Collies, Shelties, Australian shepherds, Long-haired Whippet etc.) to the MDR1 gene mutation (reduced production of p-glycoprotein) unless the patient has been tested and found not to have the gene defect. A specific test for identifying dogs that have this gene defect is now available.

Question 48

What dosage form is commonly used to give ivermectin to horses?

Answer 48

Usually pastes that are administered p.o.

Question 49

Doramectin use

Answer 49

potentially used for generalized demodicosis in small animals

Question 50

What are selamectin and eprinomectin?

Answer 50

They are topical avermectin antiparasiticides for cattle, dogs and cats. The topical administration is along backline in a narrow strip from the withers to the tailhead.

Question 51

Name the active substances of milbemycins

Answer 51

Moxidectin and milbemycin oxime

Question 52

Moxidectin use

Answer 52

It is a chemically modified derivative of nemadectin (a fermentation product).It has a broad range of activity against nematode and arthropode parasites

Question 53

Use of milbemycin oxime

Answer 53

It is a fermentation product and has activity against certain arthropods and nematodes. Is used to prevent heartworm disease and Ancylostoma spp. of dogs.

Question 54

Name the active substances of tetrahydropyrimidines

Answer 54

Morantel, Oxantel, Pyrantel

Question 55

Tetrahydropyrimidines mechanism of action

Answer 55

Their primary mode of action is to affect the worm neuromuscular system leading to paralysis and death. Tetrahydropyrimidines have been used to control of benzimidazole resistant worms, but like levamisole, resistance has been demonstrated also against these drugs.

Question 56

Morantel use

Answer 56

The tartrate of morantel is used in form of bolus (so called "paratect" slow release bolus) placed in rumen. The active substance is slowly released from bolus protecting the animal for 90 days against adult and larval nematodes, but not lungworms in cattle.

Question 57

Oxantel use

Answer 57

It is effective only against Trichuris vulpis usually used in combination with pyrantel.

Question 58

Pyrantel use

Answer 58

It is usually used as the pamoate salt for treating nematodes in dogs. At double dose it is effective against horse tapeworms.

Question 59

Active substances of organophosphorus compounds

Answer 59

Dichlorvos, Haloxon, Trichlorphon

Question 60

Organophosphorus compound mechanism of action

Answer 60

Their mode of action is to inhibit the enzyme acetylcholinesterase of worms leading to paralysis and death. But also deplete the ACHE of the host, and so are not always well tolerated by mammaIs.

Question 61

Why are organophosphorus compounds not used as much anymore?

Answer 61

However, because of their relative toxicity, limited efficacy against immature stages, narrow margin of safety, and contamination of the environment through fecal excretion, their use has declined.

Question 62

Dichlorvos use

Answer 62

Dichlorvos is particularly useful in pigs against all major adult nematodes and was one of the first broad-spectrum anthelmintics to be used in this species.

Question 63

Haloxon use

Answer 63

It is used against GI nematodes in pigs and horses

Question 64

Trichlorphon use

Answer 64

It is a pro-drug of dichlorvos used mainly in horses against certain GI nematodes and bots

Question 65

Heterocyclic compound active substances

Answer 65

piperazine, diethylcarbamazine, phenothiazine

Question 66

Heterocyclic compound mechanism of action

Answer 66

Worms suffer from hyperpolarization of their muscles what produces paralysis and the worms are eliminated with faeces. The compouds exert „curare-like“ effects on susceptible nematodes, thereby paralyzing or narcotizing the worm and allowing it to be passed out with the faeces. The neuromuscular blocking effect is believed to be caused by blocking acetylcholine at the myoneural junction. In ascarids, succinic acid production is also inhibited.

Question 67

Piperazine use

Answer 67

Piperazine is still used against ascarid and oxyurid worms with 95 - 100% of effectivity upon adult forms.

Question 68

Diethylcarbamazine use

Answer 68

It is a derivative of piperazine with activity against lung- worms but it is more important in the control of canine heartworm disease In areas, where heartworm is endemic dietylcarbamazine is used for prophylaxis by daily treatment

Question 69

Phenothiazine use

Answer 69

Not used often

Question 70

Miscellaneous nematocidal compounds

Answer 70

Emodepside, Nitroscanate

Question 71

Emodepside use

Answer 71

It is currently available in some countries in combination with praziquantel (for treatment of cestode infections) as a topical formulation for the treatment of ascarids and hookworms in cats and as an oral formulation for the treatment of ascarids, hookworms, and Trichuris in dogs For dogs, emodepside is also available in combination with toltrazuril as an oral suspension for coccidia and GI nematode control.

Question 72

Nitroscanate use and mechanism of action

Answer 72

Nitroscanate, like the substituted phenols, probably acts by uncoupling oxidative phosphorylation. It is used in small animals (dogs) against Toxocara, Toxascaris, Taenia, Dipylidium, Ancylostoma, Uncinaria, and Echinococcus spp.

Question 73

What are antiparasitics effective against flukes called?

Answer 73

Antitrematodal dugs or flukicides

Question 74

What are flukes and which animals are they commonly a problem in?

Answer 74

Flukes can be seriously harmful to grazing livestock, especially sheep, but also cattle, particularly in humid regions that offer an adequate environment for the intermediate hosts (typically snails and other mollusks). Flukes can occur in traditional pig and poultry production, but are usually not an issue in industrial operations. Flukes are seldom a problem for pets, especially in urban environments nor for horses. In fact, there are almost no veterinary medicines for controlling flukes on dogs, cats or horses, very few for pig and poultry, but numerous brands for sheep and cattle.

Question 75

Classification of antitrematodal drugs and their active substances

Answer 75

1. Halogenated salicylanilides: oxyclozanide, closantel, rafoxanide 2. Halogenated phenols: nitroxynil, niclofolan 3. Phenoxyalcans: diamphenethide 4. Benzimidazoles: albendazole, luxabendazole, triclabendazole 5. Organophosphates: trichlorphon, bromphenophos

Question 76

Halogenated salicylanilide mechanism of action

Answer 76

Salicylanilides are uncouplers of the oxidativephosphorylation in the cell mitochondria, which disturbs the production of ATP. This seems to occur through suppression of the activity of succinate dehydrogenase and fumarate reductase, two enzymes involved in this process. This impairs the parasites motility and probably other processes as well

Question 77

Oxyclozanide use

Answer 77

It is active against adult liver flukes and 6 weeks old larvae Often mixed with broad-spectrum nematocides.

Question 78

Closantel use

Answer 78

It is an oral and parenteral fasciolicide of ruminants. It is active against adult and juvenile flukes, dirofillaria, fly larvae, mites, ticks and some cestodes.

Question 79

Rafoxanide use

Answer 79

It is efficient against both adults and larval stages. | It can be use also in another parasitosis (Gastrophillus spp., Haemonchus spp., etc.).

Question 80

Halogenated salicylanilides active substances

Answer 80

oxyclozanide, closantel, rafoxanide

Question 81

Halogenated phenols active substances

Answer 81

nitroxynil, niclofolan

Question 82

Halogenated phenols compared to halogenated salicylanides

Answer 82

They are tolerated worse than halogenated salicylanilides.

Question 83

Niclofolan use

Answer 83

It is active against adult and juvenile flukes, Paraphystomum cervi and larvae Hypoderma bovis in ruminants, pigs and horses.

Question 84

Nitroxinyl use

Answer 84

It is a low spectrum flukicide not very much used on cattle, sheep and goats because is destroyed by ruminal microorganisms so can only be used as an injection.

Question 85

Active substance of phenoxyalcans

Answer 85

diamphenethide

Question 86

Diamphenethide use

Answer 86

It is effective especially against very young flukes (from 1st day) in sheep, but it is inactive or less active in cattle.

Question 87

Benzimidazole active substances

Answer 87

albendazole, triclabendazole

Question 88

Triclabendazole use

Answer 88

It differs from other benzimidazoles in spectrum of activity, i. e. very active against liver fluke from 1 st day old to adult forms and has no antinemathodal activity.

Question 89

Why are organophosphates not used often anymore as antitrematodal drugs?

Answer 89

Trichlorphon and bromphenophos today are used only very occasionally because of their low activity (resistancy) & high toxicity.

Question 90

Which antitrematodal drug is effective against early immature, immature and mature liver flukes?

Answer 90

Check iPad pic (triclabendazole)

Question 91

Name some miscellaneous trematocidal compounds

Answer 91

Benzenesulfonamides, Clorsulon

Question 92

Clorsulon use

Answer 92

is a sulfonamide used against adult liver flukes in combination with ivermectin.

Question 93

Antiparamphistomosis drugs use and active substances

Answer 93

``` Rumen fluke (Paraphistomum spp.) infections are common in cattle and sheep. Adult flukes attach to the rumen wall. Intestinal paramphistomosis respond well to treatment with drugs effectives against liver fluke and/or cestode infection in ruminants: niclosamide, niclofolan, resorantel and bithionol. ```

Question 94

Antiparagonimosis drugs use and active substances

Answer 94

``` Lung fluke (Paragonimus spp.) infections occur in dogs and cats in the Americas and in the Far East. Apparently efficacious are bithionol, praziquantel, albendazole and fenbendazole, ```

Question 95

What are the 2 types of anticestodal drugs called?

Answer 95

Anticestodal drugs are referred to as taeniacides (cause death) or as taeniafuges (facilitate tapeworm expulsion).

Question 96

What is the aim of anticestodal treatment?

Answer 96

The aim of satisfactory treatment of tapeworm infection is the complete removal of the parasites, including the scolexes, by which the parasite is attached to the mucosa. Today a taeniacidal action is required.

Question 97

Characterize the newer anticestodal drugs

Answer 97

The newer modern anticestodal drugs remove also scolexes, have activity in various animal species and are tolerated well.

Question 98

What are the most important anticestodal drugs?

Answer 98

synthetic compounds: niclosamide, praziquantel, epsiprantel, bunamidine, resorantel, dichlorphen, nitroscanate

Question 99

Describe niclosamide and it’s use

Answer 99

It is a salicylanilide derivative used as an oral tapeworm remedy. Activity: It is effective against cestodes Echinococcus, Taenia spp., Dipylidium caninum in dogs and cats and in ruminants against intestinal flukes such as Paramphistomum spp. In some countries it is also used in cattle and sheep against Moniezia benedeni infections and in horses against species of Anoplocephala magna.

Question 100

Niclosamide mechanism of action

Answer 100

Mode of action is based on an attacking the proteosynthesis of worms and inhibition of oxidative phosphorylation.

Question 101

What is praziquantel and what is it’s use?

Answer 101

``` It is an excellent taenicide belonging to the chemical class of the isoquinolines. It is very much used in dogs and cats but it is less used in livestock or birds. ``` Already in very low doses it is effective against larvae from 4 days old. It is active against scolexes, which are expulsed from GIT. In higher doses eliminates 90% of Dicrocoelium dendriticum (small hepatal fluke).

Question 102

Praziquantel mechanism of action

Answer 102

It affects the permeability, facilitates Na a Ca ions to penetrate through the membrane in muscles. As consequence the worms are paralysed and die. It also affects carbohydrate metabolism and causes a vacuolization of the tegument.

Question 103

How often must Niclosamide and Praziquantel need to be administered for prophylaxis.

Answer 103

Praziquantel and niclosamide are administered in dogs 2-4 times a year for prophylaxis to avoid the infection by cestodes.

Question 104

Praziquantel toxicosis and when not to use

Answer 104

Toxicity occurs at 40 times the therapeutic dose in dogs, the only toxic symptoms seen is occasional vomiting. The injection is painfull. It is not recommended to be given to puppies under 4 weeks of age and kittens under 6 weeks.

Question 105

Name the combinations of Praziquantel with other active substances

Answer 105

praziquantel + pyrantel praziquantel + pyrantel + febantel Praziquantel + emodepside

Question 106

Describe epsiprantel and its use

Answer 106

It is a isoquinoline derivative very potent and safe novel tapeworm remedy with excellent oral activity against tapeworms in dogs, cats, sheep and horses.

Question 107

Describe dichlorphen and its use

Answer 107

It is a phenol derivative, extremely well tolerated in dogs and cats, but only of narrow spectrum activity. It has moderate activity against Taenia spp. and Dipylidium spp. in dogs, but is ineffective against Echinococcus spp. Worms are killed in the gut, disintegrated prior to expulsion.

Question 108

Describe nitroscanate and what animals is it used in?

Answer 108

It is a phenylthiocyanate derivative active against tapeworms in dogs. It may be used in young puppies, pregnant and lacting bitches.

Question 109

Bithionol use

Answer 109

It is a phenolic compound used for treatment of tapeworm infection in dogs, cats, poultry and ruminants. It is highly effective in dogs against Taenia spp., but less against Dipylidium spp. In poultry against Raillietina spp., in ruminants against Moniezia spp. and Paramphistomum spp.

Question 110

Describe resorantel and its use

Answer 110

It is a resorcylanilide derivative with highly activity against Moniezia spp. in ruminants and also against Paramphistomum spp.

Question 111

Name some acanthocephalic drugs

Answer 111

dichlorophen, bithionol, thiabendazole, albendazole, niclosamide. However in last years there are in verification also newer generations of agents tested for the effectivenes against acanthocephala (loperamid).