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Treating Bipolar disorder: antimanic drugs > Antiepileptics- Li resistant mania or acute( lamotrigine, valproate,carbamazepine) > Flashcards

Antiepileptics- Li resistant mania or acute( lamotrigine, valproate,carbamazepine) Flashcards

1
Q

general features

A
  1. 1% prevalance (most common after stroke)
    2.chronic disorder needing life long treatment
    3.
    -seizures: recurrent, episodic, high frequency abnormal discharge of cortical neurons which might spread to other brain regions.
    -epilepsy: primary disorder of unpredictable and periodic recurrent unprovocted seizures.
  2. Central excitatory NT enhanced ( glutamate)
  3. Inhibitory NT decreased ( GABA)
  4. Cause epilepsy:
    no reason, idiopathic (50%)
    can be caused by tumor, infection,drug toxicity &withdrawal, hypoglycemia, injury or stroke
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2
Q

Partial/Focal seizures

A

-focus (discharge) is localised in a certain brain region
-based on the symptoms you can find the region of discharge
-eg symptoms of paresthesia–> sensory region
symptoms of muscle fasciculations–> motor region
autonomic regions–> brainstem affected

two types:
A. simple ( consciousness is maintained)
B. complex (consciousness is lost)
C. secondary generalised partial seizured

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3
Q

Generalized seizures

A

-bilateral, pts lose consciousness

types:
A. Grand Mal
-first loss of consciousness, then:
-“tonic phase”: increased muscle tone typically the back muscles
-“Clonic phase”: 1-2 min muscle shaking, mainly arms and legs
-Consciousness arrives back slowly
-post ictal sleep, confusion and amnesia

B. Petit Mal (Absence seizures)

  • starts usually in childhood
  • 10-20 sec loss of consciousness
  • not observable as a seizure
  • neuronal firing in thalamus caused by T-type calcium channels

C. Myoclonic seizures
-1 sec long muscle contractions

D. Atonic seizures
-all muscle tone lost

E. Lennox-Gastau

  • severe, usually in children
  • mental retardation also ( severe or progressive)

F. West syndrome

  • in newborns
  • they cross arms and move their head
  • develops to Lennox G. or disappears (the benign type)

G. Status epilepticus

  • repetitive seizures
  • grand mal type
  • consciousness not gained back between 2 seizures or there is one long seizure 30min long (can cause hypoxia and brain damage)
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4
Q

Treating generalised tonic/clonic & partial seizures ways

A
  1. Na+ channel blockers
    - resting/active/inactive
    - high affinity for inactive conformation. ‘selectivity’ they bind to neurons that have higher frequency with better affinity.
    - acute neurologic side effects (sedation,dizziness,ataxia,tremor,dyplopia and nystagmus-slowly diminished in course of treatment)
  2. GABAergic drugs
  3. Drugs with complex mechanism of action
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5
Q

Name the Na+ channel blockers

A
  1. Phenytoine
  2. Fosphenytoine
  3. Carbamazepine
  4. Oxcarbamazepine
  5. Primidone
  6. lamotrigine: all seizures &mood stabilizers (less teratogenic than others)
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6
Q

Phenytoine indications

A

-Blocks high frequency firing neurons
-orally or IV( need carrier solvent)
-changeable elimination!!! :
<300mg/day: linear eliminatinon proportional to serum level. 6-24 hr 1/2life
>300mg/day: 0 order(non linear) not proportional to serum level. 5 day 1/2life.
It is metabolised by CYP2C9, 2C19 and those enzymes seem to be saturated at these concentrations

  1. generalised clonic/tonic &partial seizures
  2. epileptic state
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7
Q

Phenytoine side effects

A

acute/neurological typical for all Na+ channel blockers:

  1. drousiness
  2. dizziness
  3. ataxia
  4. dyplopia/nystagmus
  5. tremor

diminished during treatment:

  1. gingival hyperplasia
  2. osteomalacia
  3. teratogenic (cleft lip)
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8
Q

Interactions of Phenytoine

A

-It is an enzyme inducer:
activates CYP3A4 which is responsible for the metabolism of 60% of drug metals
so accelerated drug metabolism and effect is diminished eg antigoaculants and contraceptives (not effective anymore)

-also belongs to class 1B antiarrythmic agents
IV will cause arrhythmias-basically caused by the solvent, propyline gycol
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9
Q

Fosphenytoine

A
  • more soluble but less effective

- no solvent needed so not arrythmogenic

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10
Q

Carbamazepine

A

indications same as phenytoine plus:

  1. trigeminal neuralgia
  2. lithium resistant mania
  3. acute alcohol withdrawal syndrome
  • given orally
  • metabolised by CYP3A4 & CYP2C9 and enhances the activity of these enzymes so basically enhances its elmination 36hr–> 20hr

side effects:

  1. acute neurologic effects
  2. chronically causes bone marrow suppression
  3. fluid retention (rarely)
  4. teratogenic
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11
Q

Oxcarbamazepine

A
  • analogue of carbamazepine
  • less effective though
  • less of an enzyme inducer
  • indicated for partial seizures
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12
Q

Name GABAergic drugs (5)

A
  1. Barbiturates
  2. Vigabatrine
  3. Tiagabine
  4. Gabapentine
  5. Pregabaline
  6. benzodiazepines

have:

  1. anxiolytic effect–> reduction of anxiety without influencing motor or mental functions
  2. sedative effect–> suppression of responsiveness to constant level of stimulation with decreased spontaneous activity.
  3. hypnotic effect–> producing drowsiness, promoting the onset and maintenance of a state of sleep that as far as possible resembles the natural sleep state.
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13
Q

Name the Barbiturates

mechanism of action

A
  • Long DA: Phenobarbital
  • Middle DA: Amobarbital, Pentobarbital
  • Short DA: Thiopental, Hexobarbital (during balanced anesthesia)
  • important IV anesthetics

MOA:
they facilitate the actions of GABA by increasing the duration of the GABA-gated channel openings

barbiturates not used as sedative-hypnotics now because:

  1. Low safety margin
  2. no antagonist
  3. dependance and tolerance
  4. enzyme induction
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14
Q

Phenobarbital (effect with dosage & indications)

A
  • acts on GABAa
  • slows down the dissociation and increasing the period of opening of the ion channel
  • old fashioned sedative, hypnotic but only used as an antiepileptic now

SMALL DOSE: acts as an allosteric modulator, potentiating the effect

LARGE DOSE: can activate the channel by itself! therefore can be lethal causing respiratory depression
and it might have further non-selective actions eg depression of excitatory neurotransmission.

-has narrow therapeutic range

AS YOU INCREASE DOSE:
-sedation, then sleep, anesthesia, resp depression then comma!–> dose and response is a straight line through the origin with a steep slope

indications:

  1. only for epileptic stage, 2nd line
  2. newborn hyperbilirubinemia (strong enzyme inducer)
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15
Q

Vigabatrine( side eff and indic.)

A
  • blocks GABA transaminase, increasing GABA, slight inihibition of GAT1
  • causes irreversible visual field loss
  • indicated LAST choice for partial seizures or West syndrome
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16
Q

Tiagabine( side eff and indic.)

A
  • blocks GAB transporter (GAT1) therefore blocking GABA reuptake
  • indicated for partial seizures
  • side effects: confusion, ataxia, dizziness and tremor
17
Q

Gabapentine & Pregabaline( side eff and indic.)

A
  • blocks N type Ca channels therefore decreasing Glutamate release
  • indicated for partial seizures, neuropathic pain, mania and profilaxis from migranes
18
Q

Name drugs with complex mechanism of action

A
  1. Valproic Acid
  2. Topiramate

–> broad spectrum, indicated for all type of seizures

19
Q

Valproic Acid( mech of action, indications, side effects)

A

indcations:
1. used in GrandMal and PetitMal (1st choice)
2. all other seizures
3. Lithium resistant Mania
4. Profilaxis from migrane

mechanism of action:

  1. blocks Na+ channels
  2. increases GABA ergic neurotransmission by blocking GABA transaminases
  3. blocks T type Ca channels
  4. activates glutamate decarboxylase( degrades glutamate to GABA)

side effects:

  1. tremor (blocks Na+ Channels)
  2. nausea and vomiting
  3. abdominal pain, weight gain
  4. hair loss
  5. hepatotoxicity (fatal)–> called fulminant hep and increased risk for children <2yrs of age

because it is an enzyme inducer (but less than phenytoin and carbam.):

  1. teratogenic (spina bifida)
  2. less sedative
  3. less dependance
20
Q

Topiramate (mech of action, indic. and side eff)

A
  1. blocks Na+ channels
  2. potentiates the effect of GABA
  3. Blocks AMPA

Indications:

  1. general and partial seizures
  2. absent seizures
  3. profilaxis from migrane

side effects:

  1. neurologic (bec blocks Na+ ch)
  2. weight gain
  3. kidney stones ( blocks Carbonic anhydrase)
  4. teratogenic
  5. enzyme inducer (CYP3A4 so makes contraceptives less effective)

Treating Bipolar disorder: antimanic drugs (8 decks)

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