Lecture 15: Anticonvulsants

Question 1

Seizures are ____firing of brain neurons

Answer 1

Disordered, synchronous, rhythmic firing

Question 2

Seizures may result from too much___ or too little ____

Answer 2

Glutamate, gaba

Question 3

What is the drug of choice for status epilepticus

Answer 3

Diazepam (or other benzos)

Question 4

What is the MOA for benzos

Answer 4

Bind GABAa receptor open Cl- channels resulting in hyperpolarization

Question 5

How does phenobarbital work

Answer 5

Bind GABAa receptors, open Cl- channels and hyperpolarize

Question 6

What is phenobarbital used for

Answer 6

Maintenance therapy of seizure disorders in dogs and cats

Question 7

Chronic use of phenobarbital can cause what

Answer 7

Increase P450- increase drug interactions

Question 8

What are some side effects of phenobarbital

Answer 8

PU/PD, polyphasia, sedation

Question 9

Phenobarbital can increase ___ and ___ enzymes

Answer 9

TSH and liver enzymes

Question 10

What are some adverse effects of phenobarbital

Answer 10

Liver toxicity, superficial necrolytic dermatitis

Question 11

How does levetiracetam work

Answer 11

Binds synaptic vesicular protein (SV2A) and inhibits NT release

Question 12

Levetiracetam seems to decrease ___and decrease ___

Answer 12

Likelihood of seizures and brain damage caused by seizures

Question 13

What is levetiracetam used for

Answer 13

Monotherapy or add on with phenobarbital to tx seizures

Question 14

What is the preferred tx for refractory epilepsy in dogs

Answer 14

Levetiracetam

Question 15

What are some side effects of levetiracetam

Answer 15

Sedation, vomiting, anorexia

Question 16

What is MOA of KBr

Answer 16

Br- enter via Cl- channels causing hyperpolarization

Question 17

What is KBr used for

Answer 17

Refractory seizures in dogs as monotherapy or with phenobarbital

Question 18

What species is KBr not recommended in and why

Answer 18

Cats- cause asthma d/t airway inflammation

Question 19

What anticonvulsant has greater excretion with high chloride and the owner should tell you of any dietary changes

Answer 19

KBr

Question 20

What are some side effects of KBr

Answer 20

PU/PD, polyphagia, lethargy, pancreatitis

Question 21

What are some signs of toxicity with KBr

Answer 21

Vomiting, constipation, ataxia, sedation, joint stiffness in rear limbs

Question 22

What is the MOA for gabapentin

Answer 22

Inhibits N type Ca2+ channels which are unregulated in epileptic or neuropathic pain and decreases excitatory NT release

Question 23

What is gabapentin used for

Answer 23

Adjunct tx for refractory seizures and tx of pain

Question 24

What is the MOA for felbamate

Answer 24

Multiple mechanisms- Na2+, Ca2+ and GABA

Question 25

What is felbamate used for

Answer 25

Add on for partial complex or generalized seizures that have not responded to other drugs

Question 26

Felbamate may increase ___levels

Answer 26

Phenobarbital

Question 27

Felbamate can cause ___ damage in dogs

Answer 27

Liver

Question 28

What is zonisamide used for

Answer 28

Add on for refractory epilepsy and occasionally used as monotherapy in dogs

Question 29

What are some side effects of zonisamide

Answer 29

Sedation, anorexia, vomiting, ataxia in cats

Question 30

Avoid zonisamide in what patients

Answer 30

Pregnant- teratogenic

Question 31

What is the mechanism of action of valorous acid

Answer 31

Blocks high-frequency repetitive firing on neurons, probably blocks Na+ channels and enhance GABA activity

Question 32

When is valproic acid used

Answer 32

Rarely used, use if other drugs not effective

Question 33

Valproic causes ___ especially with phenobarbital by increasing phenobarbital levels

Answer 33

Sedation

Question 34

You don’t want to give valproic acid to ___patients

Answer 34

Pregnant- teratogenic

Question 35

___toxicity can be severe with valproic acid

Answer 35

Hepatotoxicty

Question 36

What is the MOA of phenytoin

Answer 36

Blocks high frequency repetitive firing or neurons, prolongs inactivation of Na+ channels

Question 37

___is not recommended for maintenance therapy due to problems with half-life and toxicity

Answer 37

Phenytoin

Question 38

What are the problems with phenytoin half life and toxicity

Answer 38

Half life too short in dogs-ineffective Half life too long in cats- toxic

Question 39

Chronic use of phenytoin causes ___ and ___

Answer 39

Gingival hyperplasia and hepatotoxicity

Question 40

___ is used primarily as a last resort for status epilepticus (or antiarrhythmic) and as an add in to produce sedation for euthanasia

Answer 40

Phenytoin

Question 41

What is the order of drugs to tx seizures with normal liver function

Answer 41

1. Initial therapy- Phenobarbital 2. Add levetiracetam, KBr, zonisamide, gabapentin, prenatal in 3. Felbamate

Question 42

What is the order of drugs to tx seizures with abnormal liver function

Answer 42

1. KBr +/- Levetiracetam 2. Levetiracetam