Pharm 31 Objectives Flashcards
What is the pharmacodynamics of Benzodiazepines?
They bind to GABA receptors and increase the frequency of GABA linked Cl- channel opening.
What is the pharmacodynamics of Barbiturates?
At low to moderate doses they prolong the time/duration of opening the Cl- channel causing them to have a more potent effect than benzos as well as inducing their own metabolism.
What is the pharmacodynamics of Gabapentin?
Blocks voltage gated n-type calcium channel by binding to the alpha2-delta and prevents the exocytosis of neurotransmitters by presynaptic cleft, and reduced glutamate.
What is the pharmacodynamics of Pregabalin?
Blocks voltage gated n-type calcium channel by binding to the alpha2-delta just like Gabapentin but has a more potent effect and its better absorbed.
What is the Pharmacokinetics of Phenytoin?
Saturable (non-linear) metabolism and a broad spectrum hepatic enzyme inducer. (makes other drugs less effective)
What is the Pharmacokinetics of Fosphenytoin?
It has an added phosphate group which increases solubility. Compared to phenytoin it is 3x faster administered IV but not faster acting.
What is the Pharmacokinetics of Diazepam?
Has some interpatient variability d/t having an active metabolite resulting in a longer duration of action
What is the Pharmacokinetics of Lorazepam?
Less interpatient variability, medium duration of action, no active metabolite, bypass phase 1 of metabolism.
- 1st line in ER for seizures
What is the Pharmacokinetics of Clonazepam?
Less interpatient variability, medium duration of action, no active metabolite, bypass phase 1 of metabolism.
Describe the mechanism of prolonging/enhancing an inactive state of Na+ channel?
Prevents repeat firing of a neuron.
Describe the mechanism of modulation/blockage of voltage gated Ca2+ channel?
Prevents the exocytosis of neurotransmitters by the presynaptic neuron.
Describe the mechanism of Pharmacologic enhancement of GABA neurotransmission?
Causes an activation of Cl- channel and hyperpolarizes the neuron which decreases the chance of an action potential.
Describe the mechanism of inhibited glutamate neurotransmission?
Glutamate is an excitatory neurotransmitter that increases the neuron firing and action potential so by inhibiting it, it decreased the chances of a neuron firing an action potential.
What is enzyme-inducing?
Increases the rate of hepatic metabolism causes other dugs to be less effective.
- Can lad to loss of hormonal contraception’s
- Induce congenital abnormalities
- Bone loss
What is enzyme-inhibiting?
Compete or displace protein bringing sites which results in increases free/active drug levels, increasing risk for toxicity.
What anti-seizure drug has the greatest potential for teratogenicity
Valproate
What anti-seizure drugs are FDA category D for pregnant pts?
Phenobarbital Carbamazepine Phenytoin Fosphenytoin Benzodiazepines
What is 1st and 2nd line tx for generalized tonic-clonic status epilepticus?
1st: Lorazepam
2nd: Phenytoin
What is 1st and 2nd line tx for absence epilepsy?
1st: Ethosuximide
2nd: Valproate
What 2 black box warnings are on antiseizure drugs?
- Depression/suicidality
2. Abrupt discontinuation
Why is Depression/suicidality a black box warning?
Death rates from suicide are 2.5-6x higher in pts with epilepsy and some drugs may cause worsening depression or suicidal ideation.
Why is abrupt discontinuation a black box warning?
Risk of withdrawal seizers especially true with benzos and barbiturates.
How would you adjust the dose of phenytoin during a toxicity episode?
Titrate to a lower dose and monitor serum levels
How would you adjust the dose of phenytoin during an increased seizure activity?
You cannot double phenytoin as it is an increased risk for tox d/t a very narrow therapeutic range
- slowly titrate to higher dose,
- Normal dose is 300-400 for 18-64 years old, <300 for elderly, and >400 for rapid metabolizers.
