Neurological Drugs Flashcards
What is lamotrigine
An anti-convulsant
Indications for the use of lamotrigine
1) Treats seizures
2) seizures associated with Lennox-Gastaut syndrome
3) Clinical depression - used off label
What is lennox-gastaut syndrome
A severe seizure disorder of young people
How does lamotrigine work
Sodium channel blocker - inhibits glutamate release hence having an anti-convulsant activity
Adverse effects of lamotrigine
Rashes Flu-like symtpoms Visual disturbances Diszziness Drowsiness GI disturbances Aggression
Warnings of the use of lamotrigine
Contraindicated in hepatic and renal impairment!!!
Use in pregnancy only if the risks dont outweigh the benefits
Interactions of Lamotrigine
OCP, carbamzazepine, ritonavir, phenytoin and rifampicin –> all decrease its concentration as it induces its glucorindation
Interactino of lamotrigine with valproate
Increases its concentration as valproate inhibits its glucorination
What is levitaracetam
An anti-convulsant
What do we use levitaracetam for?
1) Epilepsy - partial-onset, myoclonic or tonic-clonic seizures
How does levitaracetam work
Binds to synaptic vesicle glycopratein, SV2A, inhibts presynaptic calcium channels
This reduces neurotransmitter release –> acts as a neuromodulator
Impedes conduction across synapses
Adverse effects of levitaracetam
CNS effects –> most pronounced in the first month (somnolence, fatigue, headaches, dizziness, coordination problems)
Neuropsychiatric symptoms –> agitation, hostility, apathy, depression, suciidal thoughts
SJS and TEN
Warnings of use of levitaracetam
Reduce dose in renal impairment
Cautin in pregnanct
Interactions of levitaracetam
No significant drug interactions
What is phenytoin
An anti-convulsant
Indications of phenytoin
1) Status epileptics - if benzodiazepines are ineffective
2) Epilepsy - reduce frequency of generalised or focal seizures
Actiosn of phenytoin
Reduces neuronal excitability and electrical conduction among brain cells
Binds to neuronal Na+ channels in their inactive state
Also similar effect in cardaic Purkije fibres –> accoutns for antiarrhytmic and cardiotoxic effects
Adverse effects of Phenytoin
1) Appearance change - can corase skin coarsening, acne, hirsutism, gum hypertrophy
2) Neuro effects –> cerebellar toxicity
3) Haematological disorders and osteomalacia –> inducing folic acid and vitamin D metabolism
4) Hypersensitivity
5) CV collapse and respiratory depression - if phenytoin toxicity
Effects of phenytoin overdose
CV collapse and respiratory depression
Warning of using pheytoin
Metablised by liver at zero order kinetics
Low therapeutic index
Reduce dose of phenytoin in
Hepatic impaiment
Use of phenytoin in pregnancy causes what
Fetal hydantoin Syndrome
Causes craniofacial abnormalities ad a low IQ
Discuss with specialist and take folic acid supplements before conception
Interactions of phenytoin
Phenytoin inducers P450 enzymes
However it is also metablised by P450 enzymes - hence CP450 inhbiitos increase its effect
Name some CP450 inhibitros
Amiodarone
DIltiazem
Fluconazole
What type of drugs also lower the threshold potential causing the efficacy of phenytoin to reduce
SSRIs and tricuclic antidepressants
What do we need to ensure we do after giving phenytoin via a cannula
Flush the cannula to prevent venous irritation
Give it into a large vein
What is carbamazepine
An anti-convulsant
Indications of carbamazepine
1) Epilepsy
2) Trigeminal neuralgia –> First choice to control pain and reduce frequency and severity
3) Bipolar disorder - prophylaxis option
Action of carbamazepine
Appears to nihibit neuronal sodium channels
Stabilizes resting potentials and reducing neuronal excitability
Stops spread of seizure activity
Stabilises mood in bipolar –> reduces electrical kindling in the temporal lobe and limbic system
Adverse effects of carbamazepine
1) GI Upset
2) Neuro effects - dizziness and ataxis
3) Hypersensitivity - mac pac rash affects 10% of peoples
4) Antiepileptic hypersensitivity syndrome
What is anti-epileptic hypersensitivity syndrome
Usually starts within 2 months of treatment
Severe skin reactions
Fever
Lymphadenopathy
Systemic involvement (haematological, hepatic and renal)
Warnings of carbamazepine
1) In utero causes foetal abnormalities
2) Prior anti-epileptic hypersensitivity syndrome is a contraindication
Caution of using carbamazeinpine in
Hepatic
Renal
Cardiac disesae
Increased risk of toxicity
Interactions of carbamazepine
Carbamazepine is metabolised by CPP450 enzymes
It is also an inducer of CP450 enzymes itself
Also beware of other drugs that lower the threshold potential as these decrease its efficacy e.g. SSRIs, tricyclicl anti-depressants and antipsychotics and tramadol
What is valproate
An anti-convulsant
Indications of valproate
1) Epilepsy - 1st choice
2) Bipolar - acute treatment of manic episodes and prophylaxis against recurrence
Action of valproate
Weak inhibitor of neuronal sodium channels
Also increases GABA in the brain content
Adverse effects of valproate
GI Upset
Neuro and psychiatric effects: tremor, ataxia, behavioural distrubances
Thrombocytopenia and transient increase in liver enzymes
Hypersensitvity reactions
Rare life threatening idiosyncratic reactions
Who shoudl you avoid valpraote in
Child-bearing age, around time of conceptino and the first trimester
Who should we avoid valproate in
Pregnancy
Hepatic impairment
Dose reduction if renal impairment
Interactions of valproate
Itself inhibits CP450 enzymes
Valproate itself is metablised by the CP450 enzymes
Also be aware of drugs that lower the threshold potential as these reduce its efficacy
What should we warn patients about when they start taking valproate
Tummy upset
Urgent medical advice if they have lethargy, loss of apetite, vomiting and abdo pain
Indications of L-Dopa
1) Parkinsons disease - in earlier generally use dopamine agonists but L-DOPA is integral in later treatment
2) Treatment of secondary parkinsons
Action of L-Dopa
Levodopa - a precursor of dopamine that enters the brain via a transporter
What are ropinorole and pramipexol
Dopamine agonists - these are relatively selective
Pathogenesis behind parkinsons
Deficiency of dopamine in nigro-striatial pathway - therefore via direct and indirect pathways the basal ganglia exert greater inhibitory effects on the thalamus –> this reduces excitatory input to the motor cortex hence causing symtpoms e.g. bradykinesia
What is simenet and madopar
These are L-Dopa
Adverse effects of L-Dopa
Nausea, drowsiness, confusion, hallucinations, hypotension
Wearing off effect –> symptoms worsen at end of dosage interval
On-Off effects
Cautions of L-Dopa
Cauting in elderly.existing cogntiive/psychiatric disease duet o risk of confusion/hallucinatinos
Caution in cardiovascular disease –> risk of hypotension
What do we always need to prescirbe l-dopa with
a peripheral dopa-decarboxylase inhibitor e.g. carbidopa –> to reduce its conversion to dopamine outside the brain
What should you not comibne L-DOPA with
Antipsychotics –> particularly first generation and metacloparamide due to contraidctory effects on receptors
