Epilepsy- focal Flashcards
1
Q
Carbamazepine
A
- Epilepsy- first-line choice for those with focal seizures with and without secondary generalisation and for primary generalised seizures
- Trigeminal neuralgia- first choice treatment to control pain and reduce frequency and severity of attacks
- Bipolar disorder- as an option for prophylaxis in patients resistant or intolerant of other medications
2
Q
Carbamazepine
MOA
A
- The mechanism of action is not completely understood
- It appears to inhibit neuronal sodium channels, stabilising them and so resisting membrane potentials and reducing neuronal excitability
- This may inhibit seizure activity in epilepsy control neuralgic pain by blocking synaptic transmission in the trigeminal nucleus and stabilise mood in bipolar disorder by reducing electrical kindling in the temporal lobe and limbic system
3
Q
Carbamazepine
Adverse effects
A
- The most common dose-related effect is GI upset- N&V
- Neurological effects- dizziness and ataxia
- Hypersensitivity affects around 10% of people is usually a mild skin rash
-
Antiepileptic hypersensitivity syndrome- usually people taking carbamazepine or phenytoin
- Severe skin reactions, fever, lymphadenopathy with systemic (e.g. renal, hepatic, haematological) involvement 10% mortality
- Oedema and hyponatraemia are common
4
Q
Carbamazepine
Warnings
A
- Carbamazepine exposure in utero is associated with neural tube effect, cardiac and urinary tract abnormalities and cleft palate
- Women planning pregnancy should discuss treatment with a specialist and start taking high dose folic acid supplements
- Prior Antiepileptic hypersensitivity syndrome is a contraindication to both carbamazepine and phenytoin, due to cross-sensitivity
- Carbamazepine should be prescribed with caution in patients with hepatic, renal and cardiac disease due to increased risk of toxicity
5
Q
Carbamazepine
Interactions
A
- Carbamazepine induces CYP P450 enzymes, reducing plasma concentration and efficacy of drugs that are metabolised by P450 enzymes (Warfarin, oestrogens).
- CBZ is its metabolised by these enzymes so concentration and adverse effects are increased by Inhibitors
- Complex interactions can occur with other antiepileptic drugs as most alter drug metabolism
- Drugs which alter seizure threshold- SSRI, TCA, Anti-psychotics and tramadol
6
Q
Carbamazepine
Administration and communication
A
- Switching between formulation should be avoided due to differences in bioavailability between the preparations
- Explain that treatment aims to reduce seizure frequency not cure disease
- Look for hypersensitivity reactions: rash, bruising, bleeding, high temperature or mouth ulcers (blood toxicity),
- If these occur seek medical, advise
- Advise pregnant women or those who are trying to conceive seek doctor advise
7
Q
Carbamazepine
Monitoring
A
- Treatment efficacy is monitored by comparing seizure frequency before and after starting a treatment or dose adjustment
- The most useful way to monitor safety is by asking the patient to report any unusual symptoms
- Routine FBC and LFT is unlikely to coincide with unpredictable hypersensitivity reactions
- Plasma CBZ Concentrations are not routinely measured
- Blood should be taken immediately before the next dose when CBZ concentration should be 4-12 mg/L
- Time to steady state is around 2-4 weeks after starting dose
8
Q
2nd line
A
- Lamotrigine
- Levetericetam
- Oxcarbazepine
9
Q
Give Gabapentin for refractory focal seziures
Gabapentin and pregabalin
Common indications
A
- Both drugs are used in focal epilepsies (with or without secondary generalisation), usually as an add-on treatment when other antiepileptic drugs provide inadequate control
- Both drugs are used for neuropathic pain
- Gabapentin is used for migraine prophylaxis
- Pregabalin is used in generalised anxiety disorder
10
Q
Gabapentin and pregabalin
MOA
A
- Gabapentin us closely related to GABA, the major inhibitory neurotrasmitter in the brain
- MOA although not completely understood, appears largely unrelated to GABA
- It binds with voltage-sensitive Ca2+ channels, where it presumably prevents inflow of Ca and in so doing, inhibits neurotransmitter release
- This interferes with synaptic transmission and reduces neuronal excitability
- Pregabalin is a structural analogue of gabapentin that has a similar MOA
11
Q
Gabapentin and pregabalin
adverse effect
A
- Gabapentin and pregabalin are generally better tolerate than other antiepileptic drugs. Their main side effects are drowsiness, dizziness and ataxia which usually improve in the following weeks
12
Q
Gabapentin and pregabalin
Warnings
A
- Both drugs depend on the kidneys for their elimination, so their doses should be reduced in renal impairement
13
Q
Gabapentin and pregabalin
Interactions
A
- The sedative effects of gabapentin and pregabalin may be enhanced when in combination with other sedative drugs (BZ)
- Other than this no other interactions
14
Q
Levetiracetam
Indications
A
- Monotherapy of focal seizures with or without secondary generalisation
- Ajunctive therapy of myoclonic seizures and tonic-clonic seizures
15
Q
- Levetiracetam affects intraneuronal Ca2+ levels by partial inhibition of N-type Ca2+ currents and by reducing the release of Ca2+ from intraneuronal stores
- In addition it partially reverses the reductions in GABA and glycine-gated currents induced by zinc
- Levetiracetam binds to synaptic vesicles involved in vesicle fusion and neurotransmitter exocytosis
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