Parasitology lecture: Antiparasitic Drugs

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Parasitology lecture: Antiparasitic Drugs
2015-07-02 20:34:05

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  1. Ideal characteristics of drugs
    • Selective toxicity
    • Doesnt induce resistance
    • Economical 
    • Effective and easy to apply
    • Fragrant odor
    • Environmentally safe
  2. Compounds that kill various types of internal parasites
  3. Drug that kills the worm
  4. Paralyzes worm and results in passage of the parasite alive
  5. Nonprescription drugs
    Over the counter
  6. Antinematode drugs
    • Piperazine- "Happy Jack" only kills ascarids
    • Benzimidazoles
  7. Thibendazole (TBZ)
    • Prototype
    • Treats ascarids and stongyles
    • Anti-inflammatory and antifungal 
    • Drug of choice from Ascaris lumbricoides
  8. Fenbendazole
    • Panacur
    • Anthelmintic
    • Small animals, food animals, and horse
    • Tapeworms, ascarids and ancylostoma 
    • Drug of choice in small animals for whips
  9. Organophosphates
    • Contraindicated against heartworm positive
    • Effective against Gaterophilus
  10. Organophosphate proprietary names
    • Task (dogs)
    • Equigard (Diclorous, horses)
    • Combot (Trichiofuron)
  11. Avermectin drugs
    • Ivermectin (Merial)
    • Selemectin (Zoetis)
    • Moxidectin (Bayer)
    • Doramectin (Zoetis)
    • Eprinomectin (Merial)
    • Abamectin (Merck)
  12. Ivermectin facts
    • Heartworm preventative/treatment, cattle dewormer, microfilaria treatment
    • Ivomec, Eqvalan, Heartgard
    • Kills by enhancing effects of inhibitory neurotransmitters
  13. Acetylcholine (ACH)
    Neurotransmitter released by automatic nervous system
  14. Neurotransmitters in CNS
    • Glutamate (glutamic acid)
    • Aspartate (aspartic acid)
  15. Inhibitory neurotransmitters that open chlorine channels
    • Gamma Aminobutyric Acid 
    • Glycine
  16. Pyrantel
    • Nemex, Banminth and Imathal
    • Pyrantel pamoate (Strongid C)
    • Pyrantel tartrate (Strongid T)
    • Stimulates neuro-muscle junction by mimicing acetylcholine and paralyses muscles of respiration inhibiting the enzyme acetylcholinesterase
  17. How do pyrantel and organophosphates kill?
    • Nerve comes down to muscle, sodium and potassium release acetylcholine in synapse. Impulse goes to the muscle where actin and mycin contract the muscle. Acetylcholinesterase blocked by the drug and ACH remains in neuromusclar junction sending impulses to muscles causing the muscle to run out of ATP and go into rigor. 
    • Injection of anticholinergic will block the organophosphate and pyrantel in turn stopping contraction of the muscle.
  18. External Antiparasitics
    • Chlorinated hydrocarbons
    • Organophosphates 
    • Carbamates
  19. Chlorinated hydrocarbons
    • Oldest, absorbed in body and resistant to biodegradation 
    • Requires certificate by EPA to use (Lindane)
  20. Organophosphates and Carbamates
    • Kill but decompose easily
    • Contain cholinesterase inhibitor, bind to and continue receptor stimulation
  21. 2 classes of acetylcholine receptors
    • Nicotinic
    • Muscarinic
  22. Muscarinic receptors
    Postganglionic neuron of parasympathetic (cranial and sacral)
  23. Symptoms when acetylcholinesterase are blocked
    • Salivation
    • Lacrimation
    • Urination
    • Defecation
    • Dyspnea
    • Emesis
  24. Nicotinic receptors located in 2 places
    • Between preganglionic and postganglionic neurons of both parasympathetic and sympathetic systems
    • Between spinal and cranial motor neurons and somatic motor
  25. Treatments for receptors
    • Muscarinic- Atropine or glycopyrolate
    • Nicotinic- Pralidoxime (2-PAM)
  26. Pyrethrins and Pyrethroids
    • Largest group of insecticides 
    • Derived from chrysanthemum flowers
    • Can be used with organophosphates and carbamates
  27. Amitraz
    • Mitaban
    • Upjohn Company
    • Treatment for demodex
    • OTC versions: Preventic (collar for dogs)
    • Taktic (topical/collar for cattle)
  28. Imidacloprid
    • Advantage
    • Bayer
    • Kills fleas
  29. Fipronil
    • Frontline
    • Merial
    • Fipronil Plus (with methoprene)
    • Treats fleas/ticks
    • Produces paresthesia (hair loss at site of application)
  30. IGR meaning
    • Insect growth regulators 
    • Affect immature stages of insects and prevents maturation
  31. 2 types of IGR
    • Insect development inhibitors (Lufenuron)
    • Juvenile Hormone Analogs (Methoprene)
  32. How insect development inhibitors work
    • Interferes with chitin development, unable to harden
    • Flea must bite animal
  33. How Juvenile hormone analogs works
    • Female absorbs drug and incorporates into flea egg
    • Doesnt have to bite animal to work
    • Egg wont develop or larvae will be dead on hatch
  34. Old IGR
    Nylar (Pyripoxyfen)