Anti-epileptics Flashcards
Valproate - indications ?
- epilepsy - first line for prophylaxis of tonic clonic seizures, absence, focal and myoclonic
- some Status epilepticus - those not responding to benzos
- Bipolar - acute treatment of manic and prophylaxis against recurrence
valproate - MOA?
Weakly inhibits neuronal sodium channels, stabilising resting membrane potentials and reducing neuron excitation.
+ increases GABA
valproate SE
GI upset
neuro and psych: ataxia, tremor and behaviour change
thrombocytiopenia
deranged lfts
hair loss
BMF, Pancreatitis, antiepileptic hypersensitivity syndrome
Teratogenic
Valproate warnings
not for women of child bearing age esp not in 1st trimester
avoid in hepatic impairment and reduce dose in severe renal impairment
valproate interactions
- inhibits cyp450
- increases plasma conc of lamotrigine and cyp450 drugs e.g. warfarin
valproate starting dose for epilepsy
600mg
valproate starting dose for bipolar
750mg 1-3 divided doses . maintain at 1-2g
what advice can you give to patients on valproate to avoid upset tummy
take with food
DVLA advice on valproate
Advise patients not to drive unless they have been seizure-free for 12 months, and for 6 months after changing or stopping treatment.
Carbemazepine indications
- epilepsy - prophylaxis for tonic clonic and focal
2. trigeminal neuralgia
MOA of carbemazapine
inhibit neuronal sodium channels -
SE of Carbemazapine
Gi upset
neurological effects - ataxia and dizzy
odoema
hyponatraemia
hypersensitvity - rash
antiepileptic hypersensitivity syndrome - 2 months of treatment - SJS and pyrexia
what are the teratogenic effects of carbamezapine
neural tube defects, cardiac and urinary tract problems and cleft palate
if must take during pregnancy - high dose folic acid.
what situations should you prescribe carbamezapine with caution
hepatic, renal or cardiac disease
important interactions of carbemazapine
cyp 450 inducer. do not give with cyp450 inhibiters e.g. macrolides
what two routes can you prescribe carbamezapine
PO
PR
how should you stop carbamezapine
taper slowly
gabapentin and pregabalin indications
- add on for focal epilepsies if others have failed
- neuropathic pain including painful diabetic neuropathy
- an option for generalised anxiety disorder
MOA of gabapentin and pregabalin
bind with pre-synaptic voltage sensitive calcium channels. stopping release of excitatory NTs = reduced neuronal excitability. similar structure to GABA.
same effect in peripheral nerves so reduces pain
main side effects of gabapentin and pregabalin
- drowsy
- ataxia
- dizziness
improve after first few weeks of treatment
When should the dose of gabapentin and pregabalin be reduced
when there is renal impairment
what other drugs should you be careful prescribing gabapentin and pregabalin in
benzodiazepines due to overload of sedation
what affect does gabapentin have on urine dip
Protein +ve. send protein creatinine ratio instead
Lamotrigine indications
- seizure prophylaxis in epilepsy. esp in focal, tonic clonic and absence
- bipolar depression
MOA of Lamotrigine
- reduces na influx into neuron.
- inhibits post synaptic glutamate receptor - helps depression
lamotrigine SE
Headache, drowsy, irritable, blurred vision, dizzy, GI symptoms
severe - skin rash, hypersensitivity
when should you avoid prescribing lamotrigine
if patients have hypersensitivity to other antiepileptic drugs
when should dose of lamotrigine be adjusted
moderate or severe hepatic impairment
can you use lamotrigine in pregnancy
yes - plasma concentration measurement should be considered as metabolism changes
Lamotrigine interactions
- as it is metabolised by glucoronidation - CARBAMEZAPINE, PHENYTOIN, OESTROGENS, RIFAMPICIN AND PROTEASE INHIBITORS. = conc reduces
- glucorinidation inhibited by valproate so rise in levels.
levetiracetam (keppra) indications
- seizure prophylaxis in epilepsy. - focal 1nd line or add on for myoclonic and tonic clonic
- for refractory cases of status epilepticus
moa of keppra
synaptic vesicle protein 2a (SV2A) - glycoprotein in excitatory and inhibitory synapses . keppra interferes with vesicles function = modulates neuronal excitability.
SE keppra
usually none
- drowsiness
- weakness
- dizzy
- headache
- rare - mood disturbance and psychiatric issues. suicidal ideation and serious hyepersensitivity
when is dose reduction of keppra needed
renal impairment
can you give keppra in pregnancy
yes
can and should keppra be given IV
Yes it can be given however is more expensive. also it has good bioavailability so oral and iv dose remains same
indications for benzos
- Status epilepticus and seizures
- alcohol wihdrawal reaction
- sedation for intervention
- short term anxiety or insomnia treatment
MOA of benzos
facilitate enhanced binding of GABA to GABAaR. = depress synapses
SE of benzos
drowy
sedation
coma
in overdose - loss of airway reflexes = airway obstruction and death
dependancy if ltm
abrupt cessation = withdrawal reaction
benzos - when do you adjust dose
elderly - giv elower dose
who do you avoid giving benzos
- respiratory impaired patients
NM disease patients - liver failure - can cause hepatic encephalopathy - is must then use lorazepam
what drugs to benzos interact with
- additive to sedating drugs e.g. opioids including alcoho and opioids. mostly depend on CYP450 so dont use with CYP-i.
which are the longer acting benzos
lorazepam, diazepam
what benzo is used for alcohol withdrawal
chlordiazepoxide
2nd = Di or lor
what benzo is used for sedation
midazolam - short half life
what benzo is used for anxiety and insomnia
- temazepam - no longer than 2/52
OD of benzo? what drug?
flumenazil. not in mixed OD
