Neurology Drugs Flashcards

1
Q

Phenytoin class

A

Anti-convulsants

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2
Q

Phenytoin indication

A
  1. To control seizures in status epilepticus where benzodiazepines are ineffective
  2. To reduce frequency of generalised or focal seizures in epilepsy, although drugs with fewer adverse effects and interaction are preferred.
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3
Q

Phenytoin MOA

A
  • Reduces neuronal excitability which inhibits spread of seizure activity
  • Binds to neuronal Na+ channels in their inactive state and prevents Na+ influx, therefore preventing an action potential
  • Also does this in cardiac Purkinje fibres which accounts for antiarrhythmic and cardiotoxic effects
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4
Q

Phenytoin administration

A

IV: for status epilepticus, loading dose 20mg/kg then 100mg 6-8 hourly

Oral: long-term for chronic epilepsy, 150-300mg daily

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5
Q

Phenytoin contraindications

A
  • Reduce in hepatic impairment as metabolised by liver with zero order kinetics and has a low therapeutic index
  • Associated with foetal hydantoin syndrome in pregnancy
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6
Q

Phenytoin side effetcts

A

Long-term:
Causes change in appearance: skin coarsening, acne, hirsutism, gum hypertrophy

Neurological effects: cerebellar toxicity (=nystagmus, ataxia, discoordination) , impaired cognition / cosciouness

Haematological disorders and osteomalacia due to induction of folic acid and vitamin D metabolism

Hypersensitivity: mild skin rash to life-threatening anti-epileptic hypersensitivity reaction

Phenytoin toxicity: death through cardiovascular collapse and respiratory depression

Antiepileptic hypersensitivity: 1 in 5000 patients, within 2 months treatment commencing. Features include:

  • Stevens-Johnson syndrome
  • Toxic epidermal necrolysis
  • Fever
  • Lymphadenopathy
  • Systemic involvement
  • 10% mortality
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7
Q

Phenytoin interactions

A
  • Metabolised by P450 enzymes
  • Also a P450 enzyme inducer
  • Efficacy reduced by drugs that lower the seizure threshold: SSRIs, tricyclics, antipsychotics, tramadol
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8
Q

Carbamazepine class

A

Anti-convulsant

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9
Q

Carbamazepine indications

A
  1. Epilepsy: 1st line for focal seizures ± secondary generalisation, and primary general seizures
  2. Trigeminal neuralgia: 1st line to control pain and reduce attack frequency and severity
  3. Bipolar disorder: prophylactic approach in patients resistant / intolerant to other medication
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10
Q

Carbamazepine MOA

A
  • Inhibits neuronal sodium channels and reducing excitability, similar to phenytoin.
  • Inhibits speed of transmission in epilepsy
  • Blocks synaptic transmission in trigeminal nucleus for TGN
  • Stabilises mood in BP by reducing electrical kindling in temporal lobe and limbic system
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11
Q

Carbamazepine administration

A

Oral
Rectal 2nd line
Start low dose then increase gradually

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12
Q

Carbamazepine contraidications

A
  • Associated with neural tube defects, discuss with specialist
  • Antiepileptic hypersensitivity - cross-sensitivity with phenytoin
  • Caution in hepatic / renal / cardiac disease
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13
Q

Carbamazepine side effects

A
  • GI upset: nausea and vomiting
  • Neurological: dizziness and ataxia
  • Hypersensitivity: affects 10% - maculopapular skin rash
  • Antiepileptic hypersensitivity reaction
  • Oedema and hyponatraemia due to ADH-like effect
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14
Q

Carbamazepine interactions

A
  • P450 inducer
  • Metabolised by P450
  • Complex interactions with other antiepileptic drugs
  • Efficacy reduced by drugs that lower seizure threshold: tricyclics, SSRIs, tramadol, antipsychotics
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15
Q

Sodium valproate class

A

Anti-convulsant

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16
Q

Sodium valproate indications

A
  1. Epilepsy: first line treatment for focal seizures ± secondary generalisation, and primary general seizures
  2. Bipolar disorder: acute management of manic episodes, prophylactic to prevent recurrence
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17
Q

Sodium valproate MOA

A
  • Weakly inhibits Na+ channels, stabilising membrane potential and reducing excitability
  • Increases brain content of GABA (primary inhibitory neurotransmitter)
18
Q

Sodium valproate administration

A

Oral

Sodium valproate 600mg for epilepsy

19
Q

Sodium valproate contraindications

A
  • Women of childbearing age: greatest risk of neural tube defects, foetal abnormalities (cardiac / craniofacial / limb), developmental delay
  • Avoid in hepatic impairment
  • Dose reduction in renal impairment
20
Q

Sodium valproate side effects

A
  • GI upset: nausea, gastric irritation, diarrhoea
  • Neurological / psychiatric: tremor, ataxia, behavioural disturbance
  • thrombocytopenia,
  • transient increase in liver enzymes
  • Hypersensitivity: hair loss, with subsequent air regrowth being curlier
  • Idiosyncratic: severe liver injury, pancreatitis, bone marrow failure, antiepileptic hypersensitivity syndrome
21
Q

Sodium valproate interactions

A
  • P450 inhibitor
  • Aspirin: displaces from binding site = increased adverse effects
  • Efficacy reduced by drugs that lower the seizure threshold: antipsychotics, tricyclics, SSRIs, tramadol
22
Q

Lamotrigine class

A

Anti-convulsants

23
Q

Lamotrigine indications

A
  1. Monotherapy of focal seizures, primary and secondary generalised tonic-clonic seizures
  2. Maintenance treatment of bipolar I disorder and depression
24
Q

Lamotrigine MOA

A

Inhibition of neuronal Na+ channels which prevents influx of Na+ therefore reducing neuronal excitability

25
Q

Lamotrigine contraindications

A
  1. Myoclonic seizures: may exacerbate these
  2. Parkinson’s disease: may exacerbate
  3. Hepatic and renal impairment: have caution
26
Q

Lamotrigine side effects

A

Commonly has GI and neurological disturbance

Can cause antiepileptic hypersensitivity syndrome

27
Q

Levetiracetam class

A

Anti-convulsants

28
Q

Levetiracetam indications

A
  1. Monotherapy or adjunct of focal seizures ± secondary generalisation
  2. Adjunctive therapy of myoclonic seizures and tonic-clonic seizures
29
Q

Levetiracetam MOA

A

Not understood.
May selectively prevent hyper synchronisation of epileptiform burst firing and propagation of seizure activity.
Binds to synaptic vesicle protein involved in vesicle exocytosis.

30
Q

Levetiracetam contraindications

A
  • Pancytopenia
  • Depressive thoughts
  • Ataxic gait
  • Hallucinations
  • CKD
31
Q

Levetiracetam side effects

A
GI upset 
Neurological disturbance
Nasal irritation
General malaise 
Convulsions
Rash
32
Q

Levetiracetam interactions

A
  • Sedatives
  • Anxiety drugs
  • Concurrent use can increase risk of CNS depression which may affect ability to perform skilled tasks
33
Q

Levetiracetam patient info

A

Avoid alcohol

34
Q

L-Dopa class

A

CNS agent

35
Q

L-dopa indication

A
  1. Parkinson’s disease: used to increase dopamine
36
Q

L-Dopa MOA

A
  • 60-80% decrease in dopamine in substantia nigra in symptomatic parkinson’s
  • Levodopa is precursor of dopamine, dopaminergic transmission enhanced by exogenous supply
  • Levodopa crosses blood-brain barrier and decarboxylated to dopamine
  • Newly formed dopamine stimulates dopaminergic receptors
37
Q

L-Dopa administration

A

Oral

Peripheral DOPA decarboxylase prescribed alongside to prevent peripheral dopamine synthesis. E.g. modapar

38
Q

L-Dopa contraindications

A
Caution in: 
Cushings / other endocrine disorders
DM
Convulsions
CVD
Psychiatric illness
Pulmonary disease
Susceptibility to angle-closure glaucoma
39
Q

L-Dopa side effects

A

Associated with impulse control disorders e.g. gambling, binge eating and hypersexuality

Psychiatric disturbance
Neurological disturbance
Vomiting

40
Q

L-Dopa interactions

A

Beta-blockers: hypotension