PHARMACLOGY - Antiepileptic Drugs Flashcards
What are epileptic seizures?
Epileptic seizures are a disturbance of the neuronal environment which lowers the threshold for the firing of action potentials, leading to excessive electrical activity within the cerebral cortex
What are the two main causes of epileptic seizures?
Decreased neuronal inhibition
Increased neuronal excitation
What is the main inhibitory neurotransmitter in the central nervous system?
GABA
What is the main excitatory neurotransmitter in the central nervous system?
Glutamate
What are the two possible mechanisms of natural seizure termination?
Input from subcortical areas
Development of lactic acidosis
What are the eight main anti-epileptic drugs used in veterinary medicine?
Phenobarbital
Potassium bromide
Pexion
Levetiracetam
Zonisamide
Gabapentin
Diazepam
Midazolam
Leve-tri-cetam
Which classification of drugs does phenobarbital belong to?
Barbituates
Which classification of drugs do diazepam and midzolam belong to?
Benzodiazepines
Which three anti-epileptic drugs are licensed in dogs?
Phenobarbital
Potassium bromide
Pexion
Which anti-epileptic drugs are licensed in cats?
None of the anti-epileptic drugs are licensed in cats
Describe briefly how you should manage epileptic seizures
Address any underlying causes of the epileptic seizures along with symptomatic control of the seizures with antiepileptic drugs
What are the four main purposes of chronic therapy for epileptic seizures?
Reduce frequency, severity and duration of seizures
Delay progression of seizures
Minimise post-ictal effects of seizures
Minimise the demand on owners
Which anti-epileptic drugs could be used initially for chronic therapy in dogs?
Phenobarbital
Pexion
Which anti-epileptic drug should be used if a dog is refractory to phenobarbital or pexion?
Phenobarbital combined with potassium bromide
Which anti-epileptic drugs could be used initially for chronic therapy in cats?
Phenobarbital
Levetiracetam
Diazepam
What is the therapeutic range of anti-epileptic drugs?
Therapeutic range is the serum concentration of the drug which provides optimal epileptic seizure control whilst minimising side effects
What is serum steady state?
Steady state occurs when the amount of a drug being absorbed is the same amount that’s being cleared from the body
How many half lives are reached before a drug can reach steady state?
Five half lives
What is the purpose of a loading dose of anti-epileptic drugs?
A loading dose would bring the serum concentrations of the anti-epileptic drug up to steady state quicker however is only used in emergencies due to the side affects associated with such a high dose
What is the mechanism of action for phenobarbital?
Potentiates the inhibitory action of GABA neurotransmitters
What are the five initial side affects of phenobarbital?
Polyuria
Polydipsia
Polyphagia
Sedation
Ataxia
What are the four side affects associated with long-term administration of phenobarbital?
Hepatic toxicity
Reduction is serum albumin
Increased thyroid hormone metabolism
Induction of hepatic p450 enzymes
How does the induction of hepatic p450 enzymes affect phenobarbital metabolism?
The induction of hepatic p450 enzymes speeds up the metabolism of phenobarbital
What can be done to reduce the risk of hepatic toxicity associated with long-term administration of phenobarbital?
Maintain the serum concentrations of phenobarbital within the therapeutic range
How often should you measure serum concentrations in patients on long term phenobarbital administration?
Every six months
How often should you monitor hepatic function in patients on long term phenobarbital administration?
Every six to twelve months
What is the best way to monitor hepatic function in patients on long term phenobarbital administration?
Bile acid assay
What is the mechanism of action for potassium bromide?
Bromide will influx cells via GABA receptors in preference to chloride, potentiating the inhibitory effect of GABA neurotransmitters
What are the two initial side effects of potassium bromide?
Vomiting
Anorexia
Why should you never administer potassium bromide to cats?
Potassium bromide can cause fatal pneumonia in cats
What are the four side affects associated with long-term administration of potassium bromide?
Sedation
Ataxia
Pancreatitis
Pruritis (itching)
(T/F) Pexion serum concentrations do not need to be monitored
TRUE.
What is the main purpose of emergency management of epileptic seizures?
Abolish the acute seizure activity
What are the two indicators for emergency management of epileptic seizures?
Cluster seizures
Status epilepticus
What are cluster seizures?
Cluster seizures are two or more seizures which occur within 24 hours
What is status epilepticus?
Status epilepticus is a prolonged seizure which lasts over five minutes
What are the three suitable anti-epileptic drugs for emergency treatment?
Diazepam
Midazolam
Levetiracetam
Why can diazepam also be used for chronic therapy for epileptic seizures in cats?
Diazepam has a longer half life in cats
What is the course of action if a status epilepticus seizure doesn’t terminate after emergency drug administration?
Patient should be put under sedation or general anaesthesia
