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Flashcards in Pharmacology Deck (32)
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1
Q

MOA of anti-epileptic drugs

A
  1. Enhancement of GABA action
  2. Inhibition of Na+ channels
  3. Inhibition of Ca2+ channels
2
Q

Which drugs inhibit Na+ channels?

A
  • Phenytoin
  • Carbamazepine
  • Lamotrigine
  • Oxcarbazepine
  • Valproate
3
Q

Which drugs inhibit Ca2+ channels?

A
  • Ethosuximide

- Valproate

4
Q

Which drugs enhance GABA action?

A
  • Barbiturates
  • Benzodiazepines
  • Gabapentin
5
Q

MOA of phenytoin

A

Slows the rate of Na+ channel recovery following inactivation. Prevents the repetitive firing of neurons by selectively blocking of channels which are opening and closing rapidly.

Limited clinical use - unpredictable pharmacokinetics and drug interactions

6
Q

Adverse effects of phenytoin

A
  • Nystagmus
  • Dipolpia
  • Ataxia
  • Headache, vertigo
  • Confusion
  • Skin rashes
  • Anaemia
  • Gum hyperlasia
7
Q

MOA of Carbamaepine

A

Similar MOA to phenytoin, although structurally unrelated and has less drug interactions

Slows the rate of Na+ channel recovery following inactivation. Prevents the repetitive firing of neurons by selectively blocking of channels which are opening and closing rapidly.

8
Q

Adverse effects of Carbamazepine

A
  • Diplopia
  • Ataxia
  • Sedation (high doses)
  • GIT upset
  • Mental disturbances
  • Water retention
  • Aplastic anaemia
9
Q

MOA of Ethosuximide

A

Specific for T-type calcium channels. Lowers T-type calcium currents in a dose dependent manner

No effect on sodium channels or at GABA neurons

10
Q

Adverse effects of ethosuximide

A
  • Nausea, vomiting
  • Transient lethargy or fatigue
  • Skin rashes
11
Q

Indications for valproate

A
  • Primary generalised seizures
  • Simple and complex partial seizures
  • Bipolar
12
Q

MOA of Valproate

A
  • Slows Na channel recovery from inactivation
  • Limits activity of low threshold T-type calcium channels
  • Increases activity of glutamic acid decarboxylase which increases the synthesis of GABA
  • Inhibits activity of enzymes that degrade GABA
13
Q

Adverse effects Valproate

A
  • Nausea, vomiting
  • Sedation, Increased appetite, weight gain
  • Ataxia
  • Hair loss, menstrual irregularities (infrequent)
14
Q

Indication for Na+ channel inhibitors

A

Partial and generalised seizures

15
Q

MOA Barbiturates

A

Acts on GABA A, chloride ion channel to increase the DURATION of opening

Phenobarbitone, primidone

16
Q

Indication for Barbiturates

A

Limited clinical use due to availability of other drugs with lower toxicity and adverse effects

17
Q

MOA of Benzodiazepines

A

Acts on GABA A chloride ion channels to increase the FREQUENCY of opening

Diazepam, Clonazepam*, midazolam

    • Also inhibits T-type calcium channels
18
Q

Indication for Benzodiazepines

A

Adjudicative treatment for epilepsy refractive to other antiepileptic drugs.

Acute treatment of seizures including status epilepticus

19
Q

MOA of Gabapentin

A
  • Lipophilic analogue of of GABA
  • Does not act on GABA receptors
  • Inhibits Na and Calcium channels
  • Causes an increase in intracellular GABA levels in vitro
20
Q

Adverse effects of Gabapentin

A
  • Sedatin
  • Dizziness
  • Ataxia
  • Fatigue
  • GIT irritation
  • Tremor
  • Nystagmus
  • Amnesia
21
Q

MOA of levodopa

A

Levodopa can cross the BBB. It is a precursor of dopamine which is broken down to increase the dopamine levels

22
Q

What is Levodopa co-administered with

A

Carbidopa or benserazide (dopa decarboxylase inhibitors)

These drugs do not cross the BBB. They prevent the breakdown of levodopa in the periphery to reduce the adverse effects and increase the concentration of dopamine in the brain

23
Q

Adverse effects of levodopa

A

GIT –>

24
Q

Catechol-O-Methyltransferase Inhibitor

A

Entacapone

25
Q

MOA of entacapone

A

Prolongs the action of levodopa by reducing its peripheral metabolism. Through the blockade of dopa decarboxylase by the COMP pathway.

Decreases levodopa clearance and increases the relative bioavailability

26
Q

Monoamine oxidase inhibitors

A

Selegiline, Rasagiline

27
Q

Stalevo

A

Combination of carbidopa, levodopa and entacapone

28
Q

MOA of monoamine oxidase inhibitors

A
  • Selective for MAO-B which is mainly found in dopamine containing region of the CNS
  • Protects endogenous dopamine from degradation and improves motor fluctuations
29
Q

Amantadine

A
  • 1st introduces as an antiviral drug
  • Increases dopamine release and inhibits reuptake
  • Less effective than Levodopa, loses efficacy with time
30
Q

Muscarinic receptor antagonists (Parkinson’s Disease)

A
  • Atropine, Benztropine
  • Blocks the effects of ACh
  • Used to treat tremors in Parkinsons
  • Also used to treat patients taking anti-psychotic-like medication (DA agonists) that causes PD-like symptoms
31
Q

Treatment of Huntington’s Disease

A

Drugs which block dopamine effective (dopamine receptor antagonists)

  • Haloperidol, chlorpromazine
  • Fluphenaine

Huntingtons results from:
Imbalance of dopamine (increased levels), ACh and GABA in basal ganglia

32
Q

4 main classes of glutamate

A
  • NMDA
  • AMPA
  • Kainate
  • G-protein coupled receptors or metabotropic