Topic 10 - Anticonvulsants, Antiepileptics Flashcards
Indications for Anticonvulsants and Antiepileptics
Long Term treatment of Epilepsy and Management of Status
Epilepticus
Active substances of Long Term treatment of Epilepsy
Phenobarbital
Primidone
Potassium bromide (KBr)
Levetiracetam
Imepitoin
Gabapentin
Active substances of Management of Status
Epilepticus
Benzodiazepines
- Diazepam
- Midazolam
Indications for long term treatment of epilepsy
1. When a seizure lasts longer than 5 minutes (=status epilepticus)
2. When multiple seizures occur within 3 – 6 months
3. When postictal symptoms occur for more than 24 hours
(aggression, blindness) or 3 seizures
4. Confirmed lesions in the brain (or after a head injury)
pharmacokinetics for phenobarbital
Good oral absorption
IV administration: 10– 20 minutes (status epilepticus)
Intensive metabolism in the liver (ROS → chronic liver disease?)
Autoinduction! (not in Fe)
Long half-life 37-73 h
Cplasma steady state → 4-6x half-life→ approx. 2-3 weeks! (do not change until then…)
Optimal plasma concentration (1 hour before administration) → correction
Side effects of phenobarbital
- Sedation, ataxia
- Polyphagia
- PU/PD
- Elevated liver enzymes (when ALT»_space; ALKP…)
- Idiosyncratic reactions
- hepatotoxicity (rare, plasma concentration, Feø)
- pancreatitis
- necrolytic dermatitis
Pros and cons of potassium bromide
Pros
**1.*not metabolized → not hepatotoxic
2. Long action → 1x daily administration may be sufficient
Cons
1. NOT in feline patients!
2. Emesis (food, BID)
3. Ataxia, sedation
4. Polyphagia, pruritus, paraparesis, pancreatitis
Pharmacokinetics of potassium bromide
VERY long t1/2 (Long half life)
SID usually enough, but…emesis
Monitor plasma concentrations
What does SID mean?
once daily
What does BID mean?
Twice daily
Pros and cons of levetiracetam
Pros
1. Minimal side effects (sedation, ataxia, hyporexia)
2. Slightly metabolized in the liver, excreted by the kidneys(dose decrease)
3. Short half life
Cons
1. 20 mg/kg TID-QID
2. (IV dose increase)
Phenobarbital → CYP450 → dose increase!
Pros and cons of imepitoin
Pros
1. Minimal side effects (polyphagia, sedation, PU/PD, 3. eyelid)
2. 2-6 hours half-life→ quick plateau
3. Minimal changes in kinetics in patients with impaired liver or kidney functions
Mechanism of action in case of gapapentin
Calcium channel blocker
Pharmacokinetics for gabapentin
Slightly metabolized in the liver, excreted by the kidneys (dose decrease)
Dosage of gabapentin
10-20 mg/kg TID
