Anticonvulsants Flashcards
What is epilepsy
its a chronic brain disorder characterised by recurrent (>_ 2 unprovoked seizures)
Characteristics of epilepsy
Abnormal electrical discharges
loss of consciousness
abnormal movements
odd behavior
distorted perceptions
What determines the symptoms of epilepsy
the origin of the abnormal firing
Aetiology of epilepsy
often idiopathic but various brain disorders; malformations, strokes and tremors can cause symptomatic epilepsy
Where do epileptic seizures originate from
they originate in a group of neurons (the epileptogen focus) which is hyperexcitable and discharges periodically
What is a generalised seizure
aberrant/unusual electrical discharge diffusely involves the entire cortex of both hemispheres from the onset, consciousness is usually lost
Causes of generalised seizures
from metabolic disorders
sometimes genetic disorders
Generalised seizures include
AMAIT
infantile spasm
absence seizures
tonic-clonic seizures
atonic seizures
myoclonic seizures
What is a tonic-clonic seizure
seizure that causes loss of consciousness and violent muscle contractions
Another name for tonic-clonic seizures
Grand mal
What is an absence seizure
its a type of seizure that causes brief, sudden lapses in attention.
More common in children than in adults
What is a myoclonic seizure
type of seizure that causes quick, uncontrollable muscle movement with no change in the level of awareness or consciousness.
What is an atonic seizure
a type of seizure that causes sudden loss of muscle strength.
Person may not loose consciousness
Define febrile convulsions
a fit that can happen when a child has a fever
What are focal(partial) seizures
caused by excess neuronal discharge that occurs in one cerebral cortex
Focal seizures are results from
structural abnormalities
Effect of focal seizures on consciousness
may be simple (no impairement of consciousness) or complex (decr. but not complete loss of consciousness)
Can a generalised seizure occur after a focal seizure
Yes
How to know if one is about to have a focal seizure
its preceded by an aura- may consist of sensory, autonomic or psychic sensations
How long do focal seizures last
1-2 mins
What does status epilepticus involves
Either of the following:
1. tocic-clonic seizure lasting >5-10mins
2. >_ 2 seizures between which patients do not fully regain consciousness
What does abrupt withdrawal of anticonvulsants cause
Status Epilepticus
Prophylactic drugs for Grand mal
Carbamazepine
Phenytoin
Phenobarbitone
Valproic acid
Prophylactic drugs for Petit mal in children
Ethosuximide
Clonazepam
Valproic acid
Prophylactic drugs for myoclonic and atonic seizures in children
Valproic acid
Prophylactic drugs to avoid in myoclonic and mixed seizures
Carbamazepine as it may complicate seizures
Prophylactic drugs for Status epilepticus
LD PP MC
Diazepam
Clonazepam
Phenytoin
Phenobarbitone
Lorazepam
Midazolam
Prophylactic drugs for Febrile Convulsions
Paracetamol
Diazepam
Clonazepam
Phenytoin
Phenobarbitone
Na channel blockers are
PVT LC
Phenytoin
Valproic acid
Topiramite
Lamotrigine
Carbamazepine
HV dependents Ca channel blockers are
LT
Lamotrigine
Topiramate
T-type Ca Channel blockers are
Valproic acid
*Ethosuximide
GABA Transaminase blockers are
Vigabatrin
Valproic acid
MOA of Phenytoin
blocks voltage gated Na channels
*is a CYP450 inducer
I of Phenytoin
focal and generalized tonic-clonic seizures
(all forms except absence)
Status Epilepticus
Dosage of Phenytoin
200-600mg daily
MAX: 400 mg nocte
DI of Phenytoin
Is a CYP450 inducer= exhibits zero-order kinetics
AE of Phenytoin
NV
Headaches
Disorientation
megoblastic anaemia
gingival hyperplasia
hirsutism
loss of bone density;
Idiosyncratic rash
Exfoliative dermatitis
Incr. dose of Phenytoin cause
Nystagmus
Ataxia
lethargy
MOA of Carbamazepine
Blocks NA channels–> inhibits generation of repetitive APs in epileptic focus and prevents their spread
I of Carbamazepine
1st line monotherapy for generalised tonic-clonic and partial (focal) seizures
Trigeminal neuroglia
Bipolar disorder
Dosage of Carbamazepine
200mg po bd for 2/52 then 300 mg
MAX: 900mg bd
DI of Carbamazepine
is a CYP450 Inducer–> incr. toxicity of MAOIs (tranylcypromine) by unknown mechanism;
discontinuse MAOI use 14days prior to starting Carbamazepine
AE of Carbamazepine
Sedation
Ataxia
dizziness
NV
rashes including SJS
Jaundice
Dry mouth
aplastic anaemia
Leukopenia
Hyponatraemia (esp. in elderly)
MOA of Lamotrigine
Blocks Na channels and HV dependent Ca channels
I of Lamotrigine
focal seizures
generalized seizures
absence seizures
Bipolar disorder
Lennox-Gastaut syndrome
Dosage of Lamotrigine
slow-up titration of dose essential to minimse risk of serious and life-threatening skin rxns (SJS)
AE of Lamotrigine
Blurred vision
Ataxia
Dizzines
Rash
MOA of Topiramate
Block voltage gated Na channels (AMPA)
Reduce HV Ca currents
Target Glutamate (NMDA) sites: block
Indications for Topiramate
Partial (focal) seizures
Primary generalised seizures
Migraine headache
Obesity
AE of Topiramate
Drowsiness
Fatigue
weight loss
nervousness
renal stones
glaucoma
hyperthermia
parasthesia (pins and needles)
MOA of Gabapentin
is a GABA analogue:has no effect on GABA Rs
Indications for Gabapentin
focal seizures
other: post-herpetic neuralgia
Dosage of Gabapentin
dose-dependent in renal disease is required
Gabapentin dose in elderly
well-tolerated by elderly population with partial seizures with fewer DIs
AE of Gabapentin
Fatigue
Ataxia
Dizziness
Drowsiness
MOA of Vigabatrin
irreversibly inhibits GABA-T enzyme (enzyme responsible for GABA metabolism)
Indications of Vigabatrin
Infantile spasms (west syndrome)
AE of Vigabatrin
Dizziness
drowsiness
weight gain
mental confusion
psychosis
MOA of Pregabalin
binds to auxiliary subunit of voltage-gated Ca channels
Indications of Pregabalin
Focal-onset seizures
Other: diabetic peripheral neuropathy
post-herpetic neuralgia
fibromyalgia
Dosage of Pregabalin
dosage adjustments needed in renal disease
AE of Pregabalin
Weight gain
peripheral oedema
Impaired memory
MOA of Levetiracetam
Has high affinity for SV2A protein (synaptic vesicle protein) and increases/enhances its activity
Indications of Levetiracetam
Focal seizures
myoclonic
generalised tonic-clonic seizures
other: perioperative neurosurgery
AE of Levetiracetam
Mood alterations
Ataxia
dizziness
agitation
somnolence
Indications of Phenobarbitone
all forms of epilepsy except absence seizures
Dosage of Phenobarbitone
60-180 mg/day po in 1-2 divided doses
DI of Phenobarbitone
Is a hepatic enzyme inducer–> incr. metabolism of anti-epileptic drugs, estrogens and progesterone, ARV agents, alcohol or other CNS depressants- concomitant use leads to additive CNS depressants
AE of Phenobarbitone
Sedation
Ataxia
Nystagmus
Paradoxical stimulation
Behavioral and learning problems in children
megoblastic anaemia
idiosyncratic rash
MOA of Ethosuximide
inhibits T-type Ca channels–> reuced propagation of abnormal electrical activity in brain
Indications of Ethosuximide
1st line monotherapy in typical absence seizures
AE of Ethosuximide
NV
headache
sedation
ataxia
dizziness
euphoria
GIT disturbances (epigastric pain)
skin rashes- SJS
bone marrow suppression
BDZs used in seizures
CCD
Clonazepam
Clobazam
Diazepam
MOA of BDZs
bind to GABA inhibitory receptors to reduce firing rate
Indications for BDZs
reserved for emergencies of seizure attacks
Which BDZs are used for Adjunctive therapy for particular types of seizures
Clonazepam and Clobazam
Administration of Diazepam in kids
Rectal admin.
When is Diazepam also used
to avoid/interrupt prolonged generalised tonic-clonic seizures
MOA of Valproic acid
Blocks voltage gated Na channels
Blocks T-type Ca channels
Blocks GABA-T
Indications of Valproic acid
Focal
Primary generalised seizures
all forms of epilepsy
1st choice drug for patients on ART
Dosage of Valproic acid
500mg po bd
MAX: 2500mg daily
DI of Valproic acid
induces Hepatic enzymes
AE of Valproic acid
Nausea
anaroxia/incr. appetite
ataxia
sedation
hepatotoxicity
alopecia
thrombocytopenia
tetragenicity
