Anticonvulsants Flashcards

1
Q

Anticonvulsants

A

Anti-seizure, Anti-epileptic Drug used to treat seizures **Control signs not cause of problem**

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2
Q

Seizure (convulsion)

A

Clinical manifestation of abnormal activity in the brain

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3
Q

Epilepsy

A

Multiple seizures during long period of time

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4
Q

Status epilepticus

A

Seizure lasting 5+mins, or two or more discrete seizures without full recovery of consciousness between seizures

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5
Q

Anticonvulsant Causes of seizures

A

Primary Secondary Reactive

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6
Q

Primary type causes of seizure

A

Idiopathic epilepsy

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7
Q

Secondary type causes of seizure

A

Distemper Head/Injury Encephalitis CNS tumors

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8
Q

Reactive type causes of seizure

A

Fever/ Heatstroke Poisoning

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9
Q

Anticonvulsant Mechanism of action

A

Limit either the initialization or spread of seizure focus *PICTURE*

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10
Q

Anticonvulsant- Status Epilepticus At-Home treatment

A

Diazepam - Emergency! 1-2 mg/kg per rectum (teat cannula, rubber catheter) up to 3x within a 24 hour period -Suppositories, gel formations

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11
Q

Anticonvulsant- Status Epilepticus In-hospital management

A

ABC - airway, breathing, circulation STOP SEIZURES Treat cause Prevent further brain damage

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12
Q

Anticonvulsant- Status Epilepticus Stop Seizure! Treatment Name the drugs

A

Diazepam (IV, Rectal, CRI) Lorazepam Midazolam Clonazepam Clorazepate Phenobarbital General anesthesia (last resort)

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13
Q

Anticonvulsant- Status Epilepticus - Treatment Diazepam - IV

A

5-10 mg to effect ~= 0.5 mg/kg

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14
Q

Anticonvulsant- Status Epilepticus - Treatment Diazepam - Rectal

A

1-2 mg/kg if no IV access

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15
Q

Anticonvulsant- Status Epilepticus - Treatment Diazepam - CRI

A

0.5 mg/kg/h - absorption into plastics -If seizures recur after diazepam boluses

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16
Q

Anticonvulsant- Status Epilepticus - Treatment Phenobarbital

A

10-20 mg/kg IV increments to effect

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17
Q

Anticonvulsant Prevention When to start treatment?

A

More than one seizure per month Seizure within one week of head injury Brain lesion identified

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18
Q

Anticonvulsant Treatment

A

Drugs given long term Quality of life Reduce frequency & severity while avoiding serious side effects

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19
Q

Anticonvulsant - Long term treatment stats

A

Effective in about 33% Some control in 33% Ineffective in the rest

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20
Q

Anticonvulsant Benzodiazepines Used for long term treatment?

A

No! not for long-term

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21
Q

Anticonvulsant -Benzodiazepines Duration of action?

A

Short, frequent administration

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22
Q

Anticonvulsant -Benzodiazepines Cross tolerance?

A

No further use in status epilepticus Enzyme induction

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23
Q

Anticonvulsant -Benzodiazepines Oral diazepam in cats

A

Leads to fatal liver necrosis

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24
Q

Anticonvulsant - Client education

A

Client compliance Goals of treatment Potential side effects Missed dose Supply of medication Data log

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25
Q

Anticonvulsant - Drug choice criteria

A

Efficacy Safety Price Pharmacological information Clinical experience Single drug vs. combination

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26
Q

Anticonvulsant - Drug dose

A

Recommended doses are only a guide Lower end for new patients, (adjust upward as needed) Higher end of “loading dose” for frequent & severe seizures (then adjust downward)

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27
Q

Anticonvulsant - PK considerations

A

Loading Dose PK change over time (phenobarbital)

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28
Q

Anticonvulsant - PK considerations - Loading Dose

A

For drugs eliminated slowly (brombide & phenobarbital) No time for tolerance to sedative side effects

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29
Q

Anticonvulsant - Drug list

A

Peanut Butter Love Zone Feels Very Good Phenobarbital Brombide Levetiracetam Zonisamide Felbamate Valproate Gabapentin

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30
Q

Anticonvulsant Phenobarbital Length of action

A

Long-acting barbiturate

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31
Q

Anticonvulsant Phenobarbital Receptor activity

A

Potentiates GABAa receptor activity

32
Q

Anticonvulsant Phenobarbital Drug of choice in what species

A

Dog & Cat

33
Q

Anticonvulsant Phenobarbital Loading dose administration

A

Loading Dose can be given IV

34
Q

Anticonvulsant Phenobarbital Target concentration

A

Target concentration = 15-40ug/ml

35
Q

Anticonvulsant Phenobarbital Side Effects

A

Cytochrome p450 induction Sedation Hyperexcitability Restlessness Polyuria/Polydipsia/Polyphagia

36
Q

Anticonvulsant Phenobarbital Cytochrome p450 induction

A

Initial T1/2 beta in dogs ~100hrs T 1/2 beta after induction ~24hrs

37
Q

Anticonvulsant Phenobarbital Toxicosis

A

Hepatotoxicity Anorexia Sedation Ataxia Icterus Ascites

38
Q

Anticonvulsant Brombide

A

Unknown mechanism of action

39
Q

Anticonvulsant Brombide Ways it is used

A

Initial therapy or as add-on to phenobarbital

40
Q

Anticonvulsant Brombide T 1/2

A

21-24 days!

41
Q

Anticonvulsant Brombide Excretion

A

Filtered & reabsorbed in kidneys High chloride intake increases elimination

42
Q

Anticonvulsant Brombide Loading dose

A

Use NaBr if given IV KBr - congestive heart failure NaBr- hypoadrenocorticism

43
Q

Anticonvulsant Brombide Side effects

A

Vomiting Sedation Ataxia Weakness Polyuria/ Polydipsia/ Polyphagia Pancreatitis

44
Q

Anticonvulsant Brombide Toxicosis

A

Blindness Ataxia Paresis Altered behavior Dysphagia Megaesophagus

45
Q

Anticonvulsant Brombide Toxicosis protocol

A

Reduce/stop Br Diuresis (IV fluids, furosemide) Do not use in cats! Pneumonitis!

46
Q

What anticonvulsant drug should not be used in cats?

A

Brombide! Pneumonitis!

47
Q

Anticonvulsant Levetiracetam

A

Unknown mechanism of actio Synaptic vesicle protein GABA- & Glycine-gated currents Voltage-dependent K+ currents

48
Q

Anticonvulsant Levetiracetam Half life

A

T 1/2= 3-4 hours (Dogs) = 3 hrs (Cats)

49
Q

Anticonvulsant Levetiracetam Uses/ Combinations

A

Monotherapy or as add-on with phenobarbital

50
Q

Anticonvulsant Levetiracetam Side effects

A

Sedation & decreased appetite (uncommon)

51
Q

Anticonvulsant Zonisamide

A

Unknown mechanism Blocks voltage-gated sodium channels Blocks T-type calcium channels Potentiates GABAa receptors Enhances Glu uptake Reduces GABA uptake

52
Q

Anticonvulsant Zonisamide Uses/Combination

A

Monotherapy or as add-on to phenobarbital

53
Q

Anticonvulsant Zonisamide Half-life

A

T 1/2 beta = 15 hr in dogs = 35 h in cats

54
Q

Anticonvulsant Zonisamide Side effects

A

Cytochrome P450 induction Sedation, ataxia, vomiting Metabolic acidosis

55
Q

Anticonvulsant Gabapentin Mechanism of action

A

Blocks N-type voltage-gated calcium channels (a2 gamma subunit)

56
Q

Anticonvulsant Gabapentin Metabolism/Excretion

A

Excreted in urine Only partially metabolized in liver to N-methyl-gabapentin

57
Q

Anticonvulsant Gabapentin Half-life

A

T 1/2b = 2-4 hours in dogs

58
Q

Anticonvulsant Gabapentin Uses/ Combination

A

As add-on with phenobarbital & /or bromide

59
Q

Anticonvulsant Gabapentin Effect

A

Mild sedation & ataxia

60
Q

Anticonvulsant Gabapentin Oral solution

A

Oral solution contains xylitol (toxic to dogs)

61
Q

Which drug’s oral solution is toxic to dogs? What is the toxic chemical?

A

Gabapentin oral solution Contains xylitol

62
Q

Anticonvulsant Felbamate Mechanism of action

A

Potentiates GABAa receptors Blocks voltage-dependent Na+ channels Blocks NMDA receptors

63
Q

Anticonvulsant Felbamate Metabolism/Excretion

A

Dogs: 30% metabolized in liver Rest excreted unchanged in urine

64
Q

Anticonvulsant Felbamate Half-life

A

T 1/2b = 5-6 hrs in dogs

65
Q

Anticonvulsant Felbamate Uses/ combinations

A

Monotherapy or Add-on with phenobarbital

66
Q

Anticonvulsant Felbamate Effects

A

Nervousness Mild thrombocytopenia Leucopenia Hepatic disease

67
Q

Anticonvulsant Valproate Mechanism of action

A

Blocks voltage-gated Ca channels Potentiates GABAa receptors Reduces T-type calcium currents

68
Q

Anticonvulsant Valproate Half-life

A

T 1/2B = 1.5-3 hr (dogs) = 8.5 hr (cats)

69
Q

Anticonvulsant Valproate Uses/Combination

A

As add-on with phenobarbital

70
Q

Anticonvulsant Valproate Effects

A

Alopecia Hepatotoxicity Vomiting (give with food)

71
Q

Anticonvulsant Primidone

A

Approved in dogs Metabolized to phenobarbital Very Hepatotoxic More expensive than phenobarbital Not controlled, not recommended Just use phenobarbital!

72
Q

Anticonvulsant Phenytoin

A

Not reliable Not recommended Hepatotoxic

73
Q

Anticonvulsant Phenytoin Problem at high doses

A

Zero-order kinetics @ high doses

74
Q

Anticonvulsant Phenytoin Half-life

A

T 1/2b = 2hour (dogs) = ~100hr (cats)

75
Q

Anticonvulsant Phenytoin Use in horses

A

Azoturia & antiarrhythmic treatment

76
Q

Anticonvulsant Drugs to avoid!

A

P-FOB Phenothiazines Fluoroquinolones (+NSAIDS) Opioid agonists Butryophenones

77
Q

Anticonvulsant Stopping treatment

A

Seizure-free for 1-2 years -Taper dose over ~6 months -2 weeks between dose changes -Retreat if seizures return