Drugs to treat Epilepsy Flashcards
What is epilepsy?
A very common neurological disorder exhibiting periodic seizures
What are seizures?
Abnormal electrical activity in the brain
Burst of uncontrolled electrical activity between brain cells that causes temporary abnormalities in muscle tone (stiffness, twitching or limpness), behaviour, sensations or state of awareness
All seizures have convulsions. True or false
False; not all seizures have convulsions
What are convulsions?
This is when a persons body shakes rapidly and uncontrollably
Uncontrollable shaking that is rapid and rhythmic with muscles contracting and relaxing repeatedly
Describe the tonic phase of convulsions
Sudden loss of consciousness, skeletal muscles tense, extremities pull rigid towards or away from body, short (last for seconds)
briefly described as stiffening of muscle
Describe the clonic phase of convulsions
muscles contract/relax rapidly, violent shaking, eyes roll back, injury to tongue and jaw
characterised by jerking or twitching
What are the main types of seizures?
Partial seizures
Generalised seizures
What are the types of partial seizures?
Complex partial seizures
Simple partial seizures
What is a complex partial seizure?
Altered awareness and behaviour e.g. confusion, repetitive movements
What is a simple partial seizure?
remains alert e.g. jerking of a limb, nausea, strange taste or smells
Complex and simple partial seizures can lead to …
secondary generalised seizures
What is a partial seizure ?
this is when seizure activity is localised to one area of the brain
What is a generalised seizure?
this is where the seizure involves the whole brain and consciousness is affected
What is a secondary generalised seizure?
this is when seizure spreads from one area to the whole brain
What are the types of generalised seizures?
Tonic Clonic (Grand-Mal)
Absence (Petit-mal)
Tonic/atonic
Myoclonic
What is the main type of secondary generalised seizure?
Tonic Clonic (Grand-mal)
What is a tonic clonic (grand-mal) seizure?
convulsion with loss of consciousness, stiffing body then jerking limbs
What is a absence (petit mal) seizure?
staring or trance like state
What is a tonic or atonic seizure?
abrupt fall, either with stiffening muscles (tonic) or loss of muscle tone (atonic)
What is a myoclonic seizure?
sudden muscle jerks
What kinds of partial seizures lead to secondary generalised seizures
both complex and simple partial seizures
What does status epilepticus refer to?
Life threatening condition in which seizure activity is uninterrupted.
A seizure that lasts > 5 minutes or having >1 seizure in a 5 minute period without returning to a normal level of consciousness between seizures
Briefly describe the pathogenesis of epilepsy?
there is a pathologic imbalance between inhibitoy and excitatory transmission
Briefly state the MOA of anticonvulsant drugs
they control seizures either by either increasing inhibition or decreasing excitation
What are the main MOAs of anticonvulsant drugs?
Enhancement of GABA action
Inhibition of sodium channel function
Inhibition of calcium channel function
What are the functions of calcium ions in neurons?
Neurotransmitter release (diffuse into neurons and interact with vesicles, causing them to migrate to active sites)
Membrane excitability
Apoptosis (remember neurodegeneration)
List anticonvulsant drugs that enhance inhibition of signals
Phenobarbital
Benzodiazepines
Vigbatrin
Tiagarbine
Gabapentin
List anticonvulsant drugs that reduce excitation of neurons
Phenytoin
Carbamezapine
Lamotrigine
Felbamate
Topiramate
Ethosuximide
What is MOA of phenobarbital?
Enhances activation of GABA receptor (inhibit excitatory effects of glutamate)
Increases the amount of time Cl- channels are open, depressing the CNS (increase Cl- influx)
Cl- ions flow through GABA receptors into neurons causing hyperpolarisation; inhibits AP generation
What is the main use of phenobarbital?
All types of epilepsy except absence seizures
What are the adverse effects of phenobarbital?
Sedation
Depression
Give examples of benzodiazepines used as anticonvulsants
Clonazepam
Diazepam
Lorazepam
What is the MOA of benzodiazepines?
Enhance activation of the GABAa receptor
Potentiate the action of GABA; increase the power
What is the main use of benzodiazepines as anticonvulsants?
All epilepsy types
What benzodiazepines control status epilepticus?
IV lorazepam
Diazepam
What are the main adverse effects of benzodiazepines?
Sedation Withdrawal syndrome
What is the MOA of vigabatrin?
GABA transaminase inhibitor (irreversible)
Prevents GABA metabolism
What is the main use of vigabatrin as an anticonvulsant?
Partial seizures with or without secondary generalised when other drugs are ineffective
What are the main adverse effects of vigabatrin?
Sedation
Irritability
Peripheral visual defects
Psychosis (rare)
What is the MOA of tiagabine?
Inhibits GABA uptake (it is a GABA analogue)
What is the main use of tiagabine as an anticonvulsant?
Partial seizures with or without secondary generalised when other drugs are ineffective
What are the main adverse effects of tiagabine?
sedation
dizziness
confusion
tremor
What is the MOA of gabapentin and pregabalin?
may affect synthesis and release of GABA
They may also inhibit voltage gates Ca2+ channels ?- doesn’t this mean less calcium to stimulate GABA release?
They can prevent release of excitatory neurotransmitters
What is the main use of gabapentin and pregabalin as anticonvulsants?
Partial seizures with or without secondary generalised when other drugs are ineffective
What are the main adverse effects of gabapentin and pregabalin?
Sedation
Dizziness
Headache
Ataxia
Nausea (well tolerated)
What is the MOA of phenytoin?
use-dependent block of voltage gated sodium channels
What is the main use of phenytoin as an anticonvulsant?
partial seizures with or without secondary generalised
What are the main adverse effects of phenytoin?
Gingival hyperplasia (maintain good oral health)
excessive hair growth (hirsutism)
Anaemia
Skin rashes
Teratogenesis (congenital malformations of embryo, fetus)
What is the MOA of carbamazepine?
use-dependent block of voltage gated sodium channels
What is the main use of carbamazepine as an anticonvulsant?
partial seizures with or wihtout secondary generalised
What are the main adverse effects of carbamazepine?
Sedation
Ataxia
Blurred vision
Water retention
hypersensitivity reactions
leukopenia
What is the MOA of lamotrigine?
voltage gated sodium channel blocker and inhibits synaptic glutamate release
What is the main use of lamotrigine as an anticonvulsant?
All epilepsy types
What are the main adverse effects of lamotrigine?
Sedation
Blurred vision
Nausea
Dizziness
ataxia
Hypersensitivity reactions
What is the MOA of ethosuximide?
T-type voltage gated Ca2+ channel blocker
What is the main use of ethosuximide as an anticonvulsant?
main drug for treating absence seizures
What are the main adverse effects of ehtosuximide?
Anorexia
Abdominal pain and diarrhoea
Nausea and vomiting
What is the MOA of valproate?
inhibits T-type voltage gated Ca2+ ion channels
Inhibits voltage gated Na+ channels
Weak inhibitor of GABA transaminase (prevents GABA metabolism)
What is the main use of valproate as an anticonvulsant?
most epilepsy types including absence seizures
What are the main adverse effects of valproate?
Nausea
Transient hair loss
weight gain
teratogenesis (congential malformations of fetus or embryo)
What is the MOA of felbamate?
positive modulator of GABAa receptors
Blocks NMDA receptors
What is the main use of felbamate as an anticonvulsant?
used mainly for severe epilepsy - Lennox Gastaut syndrome (LGS)
Only available on a limited named-patient basis
Lennos Gastaut syndrome (LGS) is a __________ onset epilepsy
Childhood
What are the main adverse effects of felbamate?
decreased appetite, nausea and vomiting, dizziness, headache
Two rare but serious effects include:
-aplastic anaemia
- hepatic failure
What is the MOA of topiramate?
Voltage gated Ca2+ blocker
Voltage gated Na+ blocker
Potentiates GABAa receptors
Inhibits glutamatergic AMPA/Kainate receptors
Weak inhibitor of carbonic anhydrase
What is the main use of topiramate as an anticonvulsant?
Partial and generalised tonic-clinic seizures
Lennox Gastaut syndrome
What are the main adverse effects of topiramate?
Sedation
Ataxia (coordination, balance and speech)
visual disturbances
parasthesias
Urinary disorders (kidney stones)
Teratogenesis
Kainate is an ionotropic glutamate receptor. True or false
True
What are the symptoms and signs of an epileptic seizure?
-may be a brief warning (variable)
-sudden loss of consciousness, patient feels rigid, falls, may give cry, and become cyanotic (tonic phase- blue or grey skin/lips)
-after 30 seconds, jerking movements of lips, tongue may be bitten in clonic phase
-may be frothing from mouth and urinary incontinence
Typically lasts a few minutes, patient becomes flaccid but remains unconscious; confusion on gaining consciousness
How to manage an epileptic seizure
- ensure pt is not at risk of any injury; do not put anything in mouth
- give oxygen to support if necessary
- do not attempt to restrain convulsive movements
- after convulsive movements have subsided place pt in recovery position and check airway
-reassure pt and offer sympathy - pt should not be sent home if they have not made a full recovery
- transfer pt to hospital if it was first episode of epilepsy of convulsion was atypical, prolonged or resulted in injury
