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Questions and Answers

Which of the following is classified as a hydantoin used for treating seizures?

  • Lamotrigine
  • Phenytoin (correct)
  • Clonazepam
  • Ethosuximide
  • What characteristic of phenytoin is highlighted as optimal for its activity?

  • Hydroxyl groups
  • Bulky C5 substitution (correct)
  • Presence of a carbonyl group
  • Aromatic benzene rings
  • Which drug is classified under oxazolidinediones?

  • Trimethadione (correct)
  • Phenobarbital
  • Felbamate
  • Zonisamide
  • Which of the following is primarily a GABA analog?

    <p>Gabapentin</p> Signup and view all the answers

    What is the primary mechanism of action for anti-seizure drugs?

    <p>Promoting synaptic inhibition or modulating synaptic excitation</p> Signup and view all the answers

    Which agent is NOT typically used for myoclonic seizures?

    <p>Ethosuximide</p> Signup and view all the answers

    Which of the following anti-seizure drugs is known for its additional uses in neuropathic pain?

    <p>Gabapentin</p> Signup and view all the answers

    What class of drugs does phenobarbital belong to?

    <p>Barbiturates</p> Signup and view all the answers

    What is a major advantage of fosphenytoin compared to traditional phenytoin?

    <p>Greater water solubility</p> Signup and view all the answers

    Which characteristic of oxazolidinedione (trimethadione) contributes to its activity against petit mal seizures?

    <p>Absence of bulky C5 groups</p> Signup and view all the answers

    What is the mechanism of action for valproic acid?

    <p>Promotes GABA transmission by inhibiting GABA metabolism</p> Signup and view all the answers

    What is the primary metabolic pathway for ethosuximide?

    <p>Excretion unchanged</p> Signup and view all the answers

    Which of the following statements is true regarding gabapentin and pregabalin?

    <p>Both are GABA analogs with minimal metabolism</p> Signup and view all the answers

    What critical effect does lamotrigine have in managing seizures?

    <p>Blocks both sodium and calcium channels</p> Signup and view all the answers

    Which methylxanthine is primarily known to act as a CNS stimulant?

    <p>Caffeine</p> Signup and view all the answers

    What is a notable side effect of felbamate that limits its use?

    <p>Aplastic anemia and hepatic failure</p> Signup and view all the answers

    Which mechanism is NOT associated with the action of Anti-Parkinson drugs?

    <p>Norepinephrine reuptake inhibition</p> Signup and view all the answers

    What is the primary therapeutic use of Levadopa in treating Parkinson's Disease?

    <p>Enhance dopamine synthesis</p> Signup and view all the answers

    Which of the following drugs acts as a DA agonist in the treatment of Parkinson's Disease?

    <p>Pramipexole</p> Signup and view all the answers

    The therapeutic effect of Amantadine in Parkinson's Disease is primarily due to its role as a:

    <p>DA agonist and reuptake inhibitor</p> Signup and view all the answers

    Which treatment option specifically targets the inhibition of COMT in Parkinson's Disease management?

    <p>Entacapone</p> Signup and view all the answers

    Anticholinergics are primarily effective in managing which symptom of Parkinson's Disease?

    <p>Resting tremors</p> Signup and view all the answers

    Selegiline and Rasagiline both act as:

    <p>Monoamine oxidase-B inhibitors</p> Signup and view all the answers

    Which neurotransmitter's deficiency is primarily responsible for the symptoms of Parkinson's Disease?

    <p>Dopamine</p> Signup and view all the answers

    Study Notes

    Anti-Seizure Drugs: Old Agents

    • Hydantoins: Phenytoin and Fosphenytoin
      • SAR: Activity increased by bulky C5 group, phenytoin's 5,5-diphenyl structure leads to maximum activity
      • Metabolism: Primarily via CYP3A4 (N-demethylation, N-oxidation), also CYP2D6 (aromatic hydroxylation)
      • Adverse Effects: Sedation, associated with 5-HT2 and 5-HT3 antagonism

    Oxazolidinedione (Trimethadione)

    • SAR: Lack of bulky C5 groups eliminates grand mal activity, but increases petit mal (absence seizure) activity
      • High toxicity limits its therapeutic use.

    Succinimide (Ethosuximide)

    • Drug of choice for absence seizures (petit mal)
      • SAR: No bulky C5 group, replaces -O- (in oxazolidinedione) with -CH2, resulting in safer drug with retained activity
      • Metabolism: ~20% excreted unchanged, via CYP 3A4 and 2E1

    Valproic acid

    • Used for both grand and petit mal seizures
      • MOA: Promotes GABA transmission by inhibiting GABA metabolism; blocks VGSC, decreasing neuronal firing
      • Adverse Effects: Limited use due to rare hepatotoxicity and teratogenicity

    Anti-Seizures: New Agents

    Iminostilbene (Carbamazepine)

    • SAR: 2 phenyl groups are essential for activity, substitutions at C10 (keto, hydroxy, acetate ester) result in less potent but still active compounds
      • MOA: Inactivation of excessive neuronal firing by VGSC blockade
      • Note: Derivatives of TCAs (tricyclic antidepressants)

    GABA Analogs (Gabapentin and Pregabalin)

    • SAR: Both are analogs of GABA (inhibitory neurotransmitter)
      • MOA: Regulates Ca+2 influx via VGCC, activating GAD (glutamic acid decarboxylase) to inhibit glutaminergic neurotransmission
      • Metabolism: Minimal

    Phenyltriazine (Lamotrigine)

    • Useful for grand mal, petit mal, and partial seizures in adults
      • MOA: Blocks VGSC and VGCC, stabilizing presynaptic neurons; inhibits glutamate release, preventing excitatory response
      • Metabolism: Glucuronidation

    Dicarbamate (Felbamate)

    • Potent and widely used, but associated with severe adverse effects: aplastic anemia and hepatic failure
      • MOA: Interacts with NMDA, decreasing glutamate transmission and reducing neuronal excitation
      • Metabolism: Via ester hydrolysis and oxidation

    CNS Stimulants

    Methylxanthines

    • Xanthine derivatives found in plants, act as CNS stimulants.

    Epilepsy

    • Disorder characterized by recurrent seizures, not caused by identifiable factors.

    Seizures

    • Symptom of disturbed electrical activity in the brain

    Generalized Seizures

    • Absence (petit mal): Brief loss of awareness, blank stare, postseizure amnesia, no loss of motor activity.
    • Myoclonic: Short duration, no loss of consciousness, involves muscular jerks.
    • Tonic-Clonic (grand mal): Bilateral muscle jerking, loss of consciousness, tonic-clonic spasms

    Partial Seizures

    • Simple: Affects an entire hemisphere or a lobe of the brain.
    • Complex: Temporal/psychomotor seizures, can be mistaken for psychotic behavior.

    MOA of Anti-Seizure Drugs

    • Drugs alter ion channel or receptor function to promote synaptic inhibition or modulate synaptic excitation.

    Sites of Action for Anti-Seizure Drugs

    Glutamate Presynaptic Neuron

    • Lamotrigine
    • Ezogabine
    • Ethosuximide
    • Valproate
    • Zonisamide
    • Benzodiazepines
    • Carbamazepine
    • Lamotrigine
    • Lacosamide
    • Oxcarbazepine
    • Phenobarbital
    • Phenytoin
    • Rufinamide
    • Topiramate
    • Valproate
    • Zonisamide

    GABA Presynaptic Neuron

    • SSAH
    • GAD
    • GABA-T
    • Vigabatrin
    • Benzodiazepines
    • Phenobarbital
    • Topiramate
    • Valproate
    • Tiagabine
    • Topiramate
    • Felbamate

    Partial and Generalized Tonic-Clonic Seizures

    • Benzodiazepines
    • Carbamazepine
    • Ezogabine
    • Lacosamide
    • Felbamate
    • Oxcarbazepine
    • Phenobarbital
    • Phenytoin
    • Pregabalin
    • Primidone
    • Rufinamide
    • Tiagabine
    • Topiramate
    • Vigabatrin

    Myoclonic Seizures

    • Felbamate
    • Lamotrigine
    • Levetiracetam
    • Valproate
    • Zonisamide
    • Gabapentin
    • Clonazepam
    • Topiramate

    Absence Seizures

    • Ethosuximide
    • Methosuximide
    • Trimethadione

    Anti-Parkinson Drugs

    • Parkinson's Disease (PD): Slowly progressive, neurodegenerative disorder affecting the extrapyramidal dopaminergic pathway

    • Clinical Manifestations:

      • Resting tremor (improved by voluntary activity)
      • Bradykinesia (slow initiation and paucity of voluntary movements)
      • Muscle and joint rigidity (postural disturbances)
    • Treatment:

      • L-A-B-A-S-E drugs and related substances: Levadopa, Amantadine, Bromocriptine, Anticholinergics, Selegiline, Entacapone

    Normal vs Parkinsonism

    • Normal: Substantia nigra, Corpus striatum, Dopamine, Acetylcholine, GABA
    • Parkinsonism: Lack of dopamine, resulting in deficient DA neurotransmitter; lack of direct stimulation for thalamus modulation (responsible for excitatory outflow to motor cortex).

    Anti-Parkinsonism

    • Drugs and Mechanism of Action:
      • Lipophilic DA Precursor: Levadopa (dopamine precursor)
      • DA Agonist and Reuptake Inhibitor: Amantadine
      • DA Agonists: Bromocriptine, Pergolide, Pramipexole
      • Anticholinergics: Treat tremor (Benztropine, Biperiden, Trihexypeħnidyl)
      • MAO-B Inhibitors: (Without hypertensive crisis): Selegeline and Rasagiline
      • COMT Inhibitors: Entacapone and Tolcapone

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