Anticonvulsants

Question 1

What do anticonvulsants do?

Answer 1

They reduce the frequency, duration, and subsequent detrimental effects of seizures.

Question 2

Benzodiazepines

Answer 2

Diazepam and Midazolam

• B-aminobutyric acid (GABA) receptor agonists
• produces an inhibitory effect to neuronal firing
• first-line Drugs
• immediate cessation of seizures

Question 3

Diazepam

Answer 3

• highly lipid soluble = passes quickly into blood-brain barrier
• short half life
• tolerance development = not a good long term drug
• causes vascular insult
• thrombophlebitis when given peripheral vessels
• formulated in propylene glycol
• absorb to plastic = reduce potency

Question 4

Midazolam

Answer 4

-shorter half-life than diazepam = CRI

Question 5

Barbiturates

Answer 5

• Used as a maintenance anticonvulsant
• E.g. phenobarbital
• increases seizure threshold by inhibiting acitivity of glutamate (excitatory neurotransmitter)
• potentiating the post-synaptic effect of GABA
• slower onset compared to benzos
• longer duration of action

Question 6

Phenobarbital

Answer 6

• increases seizure threshold by inhibiting the activity of glutamate and potentiating the post-synaptic effect on GABA
• Heavy sedation and respiratory depression
• Portion excreted unchanged by the kidneys
• avoid using or reduce dose in renal patients
• Majority inactivated by hepatic enzymes
• Causes hepatic injury if used long term

Question 7

Propofol

Answer 7

• Fast acting, short duration general anesthetic
• Enhances neuronal inhibition through GABA agonist activity
• CRI (Short duration)
• Not affected by hepatic or renal impairment
• Causes significant cardiovascular and respiratory depression

Question 8

Inhalants

Answer 8

• E.g. Isoflurane and desflurane
• Used in patients who have built a tolerance to GABAergic anticonvulsants
• Potent cardiovascular and respiratory depression
• ? If seizure activity is actually suppressed or simply hidden

Question 9

Levetiracetam

Answer 9

• decreases dose requirements of barbiturates
• Better control
• stops seizures with large safety margin
• not bound to plasma proteins
• metabolized independently of the liver
• mostly excreted unchanged by the kidneys
• secondline or inconjunction with a 1st line anticonvulsant

Question 10

Oral anticonvulsants

Answer 10

Potassium bromide, zonisamide, felbamate, gabapentin

Question 11

Gabapentin

Answer 11

• Facilitation of nonvescular GABA release
• Used as an add on to other anticonvulsant (i.e. phenobarbital or KBr)
• CNS depression = adverse side effect