pharamacology of anticonvulsants Flashcards
When can someone get a seizure? What about in epilepsy?
Anyone can get seizure if stressed enough. Epilepsy is susceptible to seizures (threshold of stress not very high to cause seizure)
When do you start medication for seizures?
More than 1 seizure or evidence that threshold for seizure is low
What is the therapeutic objective for epilepsy?
Eliminate/reduce seizures, avoid side effects of long-term epileptic drugs, return person to normal psychological/vocational activities
What is important to tell people with epilepsy?
That they cant drive car (need to tell DVLA). If you don’t you can lose license
What is key to reducing frequency and severity of allergic skin reactions with lamotrigine?
introducing lamotrigine gradaually
When is sodium valproate contraindicated and why?
Women of child-bearing age because it has reproductive toxicity - can affect fetus (teratogenic effects) leading to neural defects, decreased IQ, autism etc
What is the relationship between lamotrigine and the oral contraceptive pill? What can you do to combat this?
Lamotrigine does not effect efficacy of OCP. OCP affects efficacy of lamotrigine because oestrogen induces metabolism of lamotrigine by upregulating enzyme that metabolises lamotrigine, so decreases lamotrigine levels. Either change contraception (best choice), change to different drug, or increase dose (hard to titrate doses)
What symptoms could they have if on OCP and lamotrigine at different times?
At 2nd/3rd weeks when oestrogen is high can get decreased dose of lamotrigine and therefore more seizures. On 4th week where there is pill break and oestrogen is low may get effects of too much lamotrigine giving depressed side effects.
When hospitalized for seizure what is first line treatment? What if this is unavailable?
First line treatment is lorazepam 4mg IV as single dose initially and repeat dose after 10-20 minutes if required (if seizure not terminated after first dose). If lorazepam unavailable give IV diazepam or buccal midazolam
What is difference in seizure in hospital treatment and seizure in community treatment?
In hospital benzodiazepines used. IV lorazepam works best. In community give buccal midazolam (quick administration)
What is mechanism of lamotrigine?
Blocks voltage gated sodium channels preventing sodium ion influx, preventing depolarisation of glutaminergic neurones & reducing glutamate excitotoxicity.
What is target of lamotrigine?
Voltage gated sodium channels
What are side effects of lamotrigine?
Drowsiness, rash. Less common/serious: steven johnsons syndrome, suicidal thoughts.
Why drowsiness with lamotrigine?
Block all excitatory channels so slows down other parts of brain giving generalised depressive effect (lethargy, sleepy)
Mechanism of sodium valproate?
Inhibition of GABA transaminase so prevents breakdown of GABA, increasing concentrations of GABA in synapse and indirectly prolonging GABA in synapse by inhibiting its metabolism
