Neurology & Mental Health

what is the MOA of carbamazepine?

inhibits neuronal sodium channels :. stabilises membrane potentials and inhibits firing :. inhibits spread of seizure activity

what are the important adverse effects of carbamazepine?

• GI upset

• neurological effects

• oedema

• hyponatraemia

• skin rashes and hypersensitivity reactions

what are the warnings associated with carbamazepine?

• caution in pregnancy → when planning, discuss treatment with specialist and start taking high dose folic acid before conception

• risk of stevens-johnson syndrome is strongly associated with carriage of the HLA-B 1502 allele → han chinese and thai origin :. test for allele before treatment

• caution in hepatic, renal or cardiac disease

what are important interactions with carbamazepine?

• carbamazepine = CYP450 inducer :. reduces efficacy of drugs metabolised by CYP enzymes e.g. warfarin

• adverse effects of carbamazepine are increased by CYP inhibitors

• interactions with other anti epileptic drugs due to altered drug metabolism

• efficacy is lowered by drugs that lower seizure threshold e.g. antipsychotics, tramadol

what are administration recommendations for carbamazepine?

• take at regular intervals

• avoid brand switching

what should you communicate to patients about carbamazepine?

• signs of severe hypersensitivity → skin rashes, bruising, bleeding

• contraception programme

• advise that driving is not allowed unless they have been seizure free for 12 months and for 6 months after changing or stopping treatment

what are the monitoring and stopping requirements for carbamazepine?

• efficacy is monitored by seizure frequency

• safety is monitored by enquiry about new symptoms

• treatment should not be stopped suddenly → withdrawn gradually under specialist supervision

what is the MOA of gabapentinoids?

they inhibit pre-synaptic voltage gated calcium channels in the hippocampus :. reduces calcium entry into neurones :. inhibits release of excitatory neurotransmitters such as glutamate :. reduces neuronal excitability

• INCLUDES GABAPENTIN AND PREGABALIN

what are the important adverse effects of gabapentinoids?

• tolerated better than older antiepileptic drugs

• drowsiness, impaired concentrations, dizziness

• weight gain

• recognised as drugs of misuse and dependency → has dissociative and relaxation effects

what are the warnings associated with gabapentinoids?

• cautioned in renal impairment

• careful assessment is required to identify risk factors for substance misuse

what are the important interactions associated with gabapentinoids?

• caution with other sedating drugs e.g. benzodiazepines

• gabapentin and pregabalin have few drug interactions in contrast to other antiepileptics

what are the prescription requirements for gabapentinoids?

schedule 3 CDs :. words and figures for total quantity

• no more than a 30 day supply to be prescribed at a time

what are the monitoring and stopping requirements for gabapentinoids?

• efficacy is assessed by symptom control

• taper gradually when withdrawing

what are some clinical tips for gabapentinoids?

gabapentin may cause false positive results for detection of proteins on urine dipstick testing :. positive results should be verified by sending a sample to the lab for quantitive analysis

what is the MOA of lamotrigine?

• binds to voltage sensitive neuronal sodium channels :. sodium influx into the neurone

• impedes repetitive neuronal firing :. reduce seizure activity

what are the important adverse effects associated with lamotrigine?

• headache

• drowsiness

• irritability

• blurred vision

• dizziness GI upset

• skin rash and severe hypersensitivity reactions

what are the warnings associated with lamotrigine?

• caution in patients with hypersensitivity to other antiepileptics due to risk of cross sensitivity

• dose reduction in moderate or severe hepatic impairment

• can be used in pregnancy :. okay for women of childbearing age

what are the important interactions for lamotrigine?

• lamotrigine is metabolised by glucoronidation :. dose increase (double dose) in drugs that induce glucoronidation e.g. carbamazepine

• dose reduction in drugs that inhibit glucoronidation e.g. valproate

• severe hypersensitivity reactions are more common when lamotrigine is co-administered with valproate

what are the monitoring and stopping requirements for lamotrigine?

• efficacy is determined by seizure control and frequency before and during treatment

• safety and tolerability are determined by enquiring about adverse effects

• withdraw over a period of 2-3 months

what is the MOA of valproate?

increases activity of GAD which increases GABA :. increases primary inhibitory neurotransmitter in the brain

what important adverse effects are associated with valproate?

• GI upset

• neurological and psychiatric effects

• thrombocytopoenia and transient increase in liver enzymes

what warnings are associated with valproate?

• avoid in girls and women who could become pregnant → especially around time of conception and first trimester of pregnancy

• antiepileptic with the highest risk of foetal abnormalities

• avoid in hepatic impairment

• dose reduction in severe renal impairment

what are the important interactions associated with valproate?

• valproate = hepatic enzyme inhibitor :. risk of toxicity with lamotrigine (glucoronidation) and drugs metabolised by CYP450 enzymes e.g. warfarin

• valproate is metabolised by CYP enzymes :. conc. is decreased by enzyme inducers and increased by inhibitors

• efficacy of antiepileptics is decreased by drugs that lower the seizure threshold e.g. antipsychotics and tramadol

what are the monitoring and stopping requirements for valproate?

• efficacy assessed by comparison of seizure control before and during treatment

• safety is assessed by symptom enquiry

• measure of liver function before and during the first 6 months of treatment is advisable

• taper dose over 2-3 months if withdrawing

what important clinical tip is associated with valproate?

important interaction between valproate and carbapenems → carbapenems = enzyme inducers :. valproate conc. falls rapidly :. avoid combination

what is the MOA of levetiracetam?

inhibits synchronised firing and reduces propagation of seizure activity

what are the important adverse effects of levetiracetam?

• generally well tolerated

• drowsiness

• weakness

• dizziness and headache

• mood disturbance

• suicidal ideation and serious hypersensitivity reactions have been reported rarely

what warnings are associated with levetiracetam?

• dose reduction in renal impairment

what important interactions are associated with levetiracetam?

• few clinically significant interactions

what are the monitoring and stopping requirements for levetiracetam?

• efficacy assessed by comparison of seizure control before and during treatment

• safety is assessed by symptom enquiry → especially for mood disturbance and suicidal thoughts

• taper dose over 2-3 months if withdrawing