chapter 3 CNS - benzodiazepines, barbiturates Flashcards
Barbiturates and benzodiazepines
- enhance GABA (inhibitory NT) or gamma-aminobutryic acid
- effective sedative hynotics (sleep inducing agents)
- antianxiety
- anticonvulsants
- benzo prescribed more than barbiturates b/c fewer side effects
benzodiazepines
- bind to neuronal GABA receptor complex (enhances GABA mediated chloride influx [neuronal inhibition)
therapeutic doses
* cause sedation, skeletal muscle relaxation
* “barbitutate fast wave” on EEG
* anticonvulsant effects
indication
* anxiety, neurotic state (anger, anxiety, self‐consciousness, irritability, emotional instability, and depression)
* nervous tension
* psychosomatic illness
* delerium tremens (Severe alcohol withdrawal symptoms such as shaking, confusion, and hallucinations.)
* skeletal muscle relaxant
* anticonvulsant
* sedative
effects
* drowsiness
* clouded mind
* dysarthria (difficulty speaking)
* ataxia (loss coordination)
* behavioral disinhibition
* dermatitis (common skin irritation)
tolerance and dependence
* high dose – may l/t dependence
* abrupt withdrawal — similar to alcohol withdrawal (convulsions, hyperthermia, delerium [serious change in mental abilities. It results in confused thinking and a lack of awareness of someone’s surroundings])
interaction
additive with alcohol
Diazepam
- choice for muscle relaxation and intractable seizures
barbiturates
- bind to receptor adjacent to GABA receptor on chloride channels
- retention of GABA at its receptor => influx of cl- through channel
induces
* sedation
* euphoria
* other mood alterations
* hypnosis
* barbiturate fast wave EEG
* resp depression
* HIGH Dose — CV depression or death
indication
* epileptic sz
* component of anesthesia
* benzo + antipsychotics better alternatives
effects
* drowsiness
* clouded mind
* dysarthria
* ataxia
* paradoxical stimulation (happens when a person experiences the opposite of what the drug is intended to do) d/t bh disinhibition
* CNS depression => coma and resp arrest
* laryngospasm (vocal cords suddenly spasm (involuntarily contract or seize)
pharmcokinetics
* induce P450 enzymes - inc metabolism of phenytoin + digitoxin, coumadin, others
tolerance
* dependence much like alcoholism
* withdrawal — convulsions, hyperthermia, dlerium => death
over 40 drug interactions
Zolpidem (ambien)
non barb/benzo
- act on GABA receptor
- mimic benzo
- short term tx of insomnia
chloral hydrate
non barb/benzo
sedation for children
- reduced to trichloroethanol (potent ethanol)
effects
* mucosal irritation
* lightheadedness
* malaise
* ataxia
* all these effects similar to ethyl alcohol
phenobarbital
mephobarbital
long acting barbiturate
- excreted via kidney
- metabolized by p450 enzymes
- anticonvulsant
- induce metabolism of other drugs
amobarbital
pentobarbital
secobarbital
short acting barbiturate
- amobarbital – psychiatist use to analyze or therapeutic (introduced into carotid artery to determine hemisphere of brain)
- prior for some neurosurgical procedure
thiopental
methohexital
ultra-short acting barbiturate
- deposited in fat
- 2ndary metabolized in liver
Partial seizures
simple partial sz consist of single detectable motor, sensory, or psychological dysfunction which does not change during episode
* consciousness retained during throughout
other signs:
* jerking of arms or legs on one side body
* tingling or unusual feeling on one side of the body
* turning of head or eyes to one side
* fearful or pained look on child’s face
partial complex sz begin in focal area
* usually in temporal lobe or limbic cortex
* focal signs are often followed by automatisms (lip smacking, sweating) + dulled consciousness
other signs
* staring into space
* chewing motions
* wandering room w/o purpose
* picking at his clothing
* trying to grab for objects out of air
* unable to respond
* saying words that don’t make sense
effective drugs –
1) carbamazepine (tegretol)
2) phenytoin (dilantin)
3) clonazepam (klonopin)
4) primidone (mysoline)
5) valprioc acid (depakene) ==> sometimes
absence seizures (petite mal)
- petit mal
- generalized sz (children or teens)
- brief episodes of blank staring but no convulsions
effective drugs
* ethosuximide (zarontin)
* valproate (dyzantil)
* clonazepam
* trimethdione
generalized tonic-clonic seizures (grand mal)
- start with prolonged contraction of muscles in extension followed by cyanosis d/t arrested breathing
- pt then experience whole body clonic jerks
- Tonic seizures cause a stiffening of muscles while clonic seizures are characterized by jerking or twitching.
treatment
1) phenytoin (dilantin)
2) diazepam (valium)
3) carbamazepine (tegretol)
4) phenobarbital
5) primidone (mysoline)
status epilepticus
- continuous series of sz w/o reawakening
- can cause permanent brain damage
treatment – IV
1) diazepam (valium)
2) phenytoin (dilantin)
3) phenobarbital
diazepam (valium)
- metabolized in liver to active metabolites (prolongs)
indication
* anxiety disorder
flurazepam (dalmane)
quazepam (doral)
- active metabolites - prolong!
indication
insomnia
