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Neurology > Principles of Neuropharmacology > Flashcards

Principles of Neuropharmacology Flashcards

1
Q

What are the actions of drugs involved in neuropharmacology?

A

Alter processes controlled by the nervous system

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2
Q

What is difficult to penetrate in regards to neuropharmacology?

A

Blood brain barrier

Many drugs are lipophilic to pass barrier easily - DIAZEPAM

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3
Q

How is p-glycoprotein involved in epileptic patients?

A

PGP is over-expressed in the BBB in the epileptic focus and can cause reduction in uptake of anti-epileptic drugs

some patients can have genetically over-expressed PGP - makes tx harder - PHARMACORESISTANT

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4
Q

Epilepsy:

Name the two types:

A

Chronic disease

Status epilepticus and animals with cluster seizures

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5
Q

What are some conditions to choosing tx for seizures?

A
  1. Monotherapy
  2. Seizure frequency may influence AED choice
  3. Need to monitor plasma levels (not toxic or able to tolerant)
  4. Owner compliance + money - lifelong commitment, 2/3 of dogs respond to AED, S/E
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6
Q

What are the two different nerve terminals AED can affect?

A

Excitatory - AP strong enough in pre-synaptic membrane will trigger it in the post-synaptic membrane

Inhibitory - releasing an inhibitory neurotransmitter into synapse from pre-synaptic membrane - causing inhibitory postsynaptic potential (IPSP) in the postsynaptic neuron, bringing the membrane potential farther away from the threshold

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7
Q

What is the mode of action for drugs at the excitatory nerve terminals?

A

Drugs eg. Carbamazepine, Phenytoin can slow down how fast neurons fire

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8
Q

What drug is used as a first line treatment for Epilepsy in dogs?

A

Phenobarbital (Barbiturate)

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9
Q

Where does the drug Phenobarbital work in dogs?

A

On the GABA receptor on the post synaptic membrane of Inhibitory nerve terminals - increases GABA - increases duration of the channel open (actually less GABA needed to work)

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10
Q

Phenobarbital: (DOGS)

a) What is the dose?
b) What is its half life?
c) how long does it take to work?
d) what is the therapeutic range?
e) how is it metabolised?
f) s/e?

A

a) 2.5mg/kg BID (oral)
a) 2.5mg/kg BID
b) 24-40 hours
c) 20 mins
d) 15.0 - 35 µg/ml
e) Liver,
f) sedation, PD, polyphagia, hepatotoxicity, TT4 and FT4 reduction, can become dependent on this drug (get withdrawals)

SEVERE cases: immune-mediated neutropenia, thrombocytopenia, anaemia

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11
Q

What do you do if there is severe s/e?

A

Stop drug immediately and load with another AED (KBr)

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12
Q

Potassium Bromide (DOGS)

a) What is the dose?
b) What is its half life?
c) what is the therapeutic range?
d) how is it metabolised?
e) s/e?

A

a) 30-40mg/kg SID
b) 15-20 days
c) 0.7-1.9mg/ml/2.3mg/ml
d) excreted by kidneys
e) sedation, weakness, PU, PD, GI irritation, (pancreatitis)

Bromide toxicity rare - renal insufficiencies (IV saline)

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13
Q

What is the difference in using Phenobarbitone and Potassium bromide?

A

Their time to steady rate is different - Pb is 10-14 days and KBr is 100 days (few months)
Pb works faster
However - Pb affects the liver whereas KBr is excreted unchanged

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14
Q

What is the action of KBr as an antiepileptic drug?

A

Replace chloride around the body

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15
Q

What is a new type of AED available?

Use?

A

Imepitoin - new drug for dogs with idiopathic epilepsy

  • dogs with unsatisfied seizure control
  • good side effect profile - treat less severe cases
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16
Q

Why does treatment fail?

A
  • Change in weight
  • developed other diseases
  • Incorrect ddx
  • Incorrect drug choice (monotherapy not sufficient)
  • refractory seizures
  • Difficult owners
17
Q

What do you do if treatment fails?

A

Monitor drug levels, add anticonvulsant, consider new drug

18
Q

What is the first line choice of AED in cats?

A

Phenobarbital

19
Q

What is the difference between the effect on cats and dogs of Phenobarbital?

A

Less affect on liver enzymes - tolerate better
-2-3mg/kg PO SID/BID (can give every day)
Don’t need as much as dogs
-s/e - polyphagia, bone marrow suppression/cutaneous hypersensitivies

20
Q

What is the second AED choice in cats?

A

Diazepam

21
Q

Diazepam

a) what is the half life?
b) what is the dose?
c) what are the s/e?

A

a) half life - 15-20hours (6x a dog)
b) dose 5-10mg PO BID/SID
c) hepatotoxocosis

22
Q

What are the other drugs available for cats?

A
  • KBr (bronchial asthma)
  • Levetiracetam
  • Gabapentin
23
Q

What type of drug is diazepam?

A

Benzodiazepines

24
Q

What is a status epilepticus?

A

Seizure that has occurred over 30mins

too much seizure activity - Brain loses energy

25
Q

What can occur in the body with a seizure that has happened for 30 mins?

A
  • Arterial hypertension (stress)
  • Increased cerebral blood flow (stress)
  • Hypoxaemia
  • Hypercarbaemia (excessive CO2 - not breathing properly)
  • hyperglycaemia
  • lactic acidosis
26
Q

What occurs in the body with a seizure over 30 mins?

A
  • Continuous muscle contraction
  • hyperthermia
  • acidosis
  • myolysis (muscles start failing) - myoglobulinuria, hyperkalaemia (Renal failure)
  • Hypoglycaemia (Energy depletion)
  • Hypotension
  • Cardiac arrhythmias

Cause multiple organ failure

27
Q

What would you do initially for a patient seizuring? (Phase 1)

A

Phase 1
1. ABC
2. Place an IV catheter (sometimes give Diazepam up bum)
3. Bloods - PCV, TP, glucose, electrolytes
Future - CBC, biochem, AED serum level (careful not to overdose)
4. Fluid therapy
5. Antiepileptic drug - Diazepam, phenobarbitone

28
Q

What are the doses for Diazepam?

A

0.5mg/kg IV every 5 mins up to 3 x (if on pb give 1mg/kg)
Rectal - 1mg/kg (if on pb give 2mg/kg)
Nasal

29
Q

What are the doses for phenobarbital?

sustained antiepileptic effect

A

up to 20mg/kg in 24 hours

if on pb - 1mg/kg for each µg/ml

30
Q

What therapy do you use to maintain the patient? (Phase II)

A

Phase II

  • keep on Pb
  • can add in KBr
31
Q

What other drugs can you add in Phase III?

A

Add second line AED -

Diazepam CRI, midazolam CRI, Propofol, Levetiracetam, Ketamin

32
Q

What happens in Phase VI?

A

Prolonged anaesthesia - eg barbiturate, gas: Isoflurane

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Neurology (13 decks)

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