16 Questions
What is the term for the period of time before, during, and after a seizure?
Post-ictal
What type of seizure involves both hemispheres of the brain?
Generalised seizure
What is the term for a seizure that lasts for more than 5 minutes or where one seizure starts before the previous one has finished?
Status epilepticus
What is the purpose of anticonvulsant therapy?
To stabilise neuronal membranes to prevent depolarisation
What is the term for a seizure that involves sudden stiffness followed by jerking movements?
Tonic-clonic seizure
What is the term for seizures that occur without a known cause?
Idiopathic epilepsy
What is a characteristic of goats when it comes to metabolizing antiparasitics?
They nearly always require a higher dose of antiparasitics than sheep.
What is the mechanism of action of Benzimidazole?
Inhibiting microtubule formation by binding to β-tubulin
What is the primary mechanism of action of praziquantel against cestodes?
Increase of Ca2+ influx into cestodes.
Which antiparasitic is particularly effective against liver fluke and Barber's pole worm?
Closantel
What is the target of Levamisole?
The parasite's nicotinic ACh receptors
What is a characteristic of praziquantel's effectiveness against nematodes?
It is very poor against nematodes.
What is the significance of the rumen in the context of Benzimidazole?
It acts as a reservoir for the drug, prolonging its duration of action
What is a notable feature of praziquantel's safety profile?
It has a very wide margin of safety.
Why is Triclabendazole used for trematodes?
It is more effective than Closantel
What is the safety profile of Tetrahydropyrimidines?
They are very safe
Study Notes
Seizures
- A seizure is a sudden depolarization of a group of neurons leading to an abnormal synchronous electrical discharge from the Central Nervous System (CNS)
- Types of seizures:
- Partial seizure: involves a focal part of the brain
- Generalized seizure: involves both hemispheres of the brain
- Epilepsy: a condition associated with multiple unprovoked seizures
Ictal Periods
- Ictal: the physiological event itself (seizure)
- Pre-ictal: the period before a seizure
- Intra-ictal: the period during a seizure
- Inter-ictal: the period between seizures
- Post-ictal: the period after a seizure
Types of Seizures
- Tonic-clonic seizure (grand mal): an intense seizure characterized by stiffening (tonic) and jerking (clonic) movements
- Absence seizure (petit mal): a seizure characterized by brief periods of "tuning out"
Status Epilepticus
- A prolonged seizure lasting more than 5 minutes
- One seizure starting before the previous one has finished
Causes of Seizures
- Idiopathic epilepsy: no known cause
- Infectious causes:
- Toxoplasmosis
- Neosporosis
- Cryptococcosis
- Neoplasia (tumors)
- Toxins:
- Snail pellet
- Snake bite
- Strychnine
Anticonvulsant Therapy
- Goal: stabilize neuron membranes to prevent unwanted depolarization
- Mechanisms:
- CNS depression (most anticonvulsants)
- Poorly understood mechanisms (some anticonvulsants)
- Examples of anticonvulsants:
- Benzodiazepines
- Imepitoin
- Barbiturates
- Propofol
- Potassium bromide
- Levetiracetam
- Gabapentin
Seizure Management
- Two scenarios:
- Stopping a seizure that is occurring (seizure treatment)
- Preventing a future seizure (seizure prevention)
Antiparasitics in Goats and Sheep
- Goats metabolize antiparasitics faster than sheep, requiring higher doses.
- Praziquantel is the gold standard against cestodes, with a wide margin of safety.
Praziquantel
- Effective against cestodes, with some activity against trematodes and poor activity against nematodes.
- Modes of action (MOA) include increasing Ca2+ influx into cestodes and release from intracellular stores, leading to neuromuscular toxicity and paralysis.
Antitrematodals
- Closantel is effective against trematodes (flukes) and has some activity against nematodes.
- Effective against Haemonchus contortus (Barber's Pole Worm), with varying resistance levels.
- MOA involves complex spastic paralysis.
- Has good oral bioavailability, extensive protein binding, and a long elimination half-life.
- Mainly used in sheep for Barber's Pole Worm and Liver fluke.
Benzimidazole
- Binds to β-tubulin, inhibiting microtubule formation, disrupting cell division and maintenance.
- Has a wide safety margin.
- Broad-spectrum anthelmintic, effective against adult nematodes, trematodes (weak, except triclabendazole), and cestodes (weak).
- Rumen acts as a reservoir for the drug, prolonging its duration of action.
- Widespread resistance in ruminants, less so in other animals.
Triclabendazole
- More effective against trematodes than closantel.
Levamisole
- Agonist at the worm's nicotinic ACh receptors, leading to sustained muscle contraction and spastic paralysis.
- Has a narrow safety margin (2-6x).
- Water-soluble, used in in-water medication.
- Effective against nematodes only.
- Still used in combination drenches for sheep.
Tetrahydropyrimidines
- Mainly used in small animals.
- Causes spastic paralysis in nematodes.
- Closely related to levamisole (the "clear" drench).
- Very safe, used in puppies and kittens.
- Dog dose rate: 6.6mg/kg once.
- Toxic to dogs at 50mg/kg sid x 3 months.
- Includes pyrantel and oxantel.
Test your knowledge on seizures, partial and generalized seizures, epilepsy, and ictal periods. Learn about the different types of seizures and their characteristics.
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