Anxiolytics and Hypnotics Flashcards
What are the benzos considered to have long half lives?
- chlordiazepoxide, diazepam, prazepam, clorazepate, flurazepam
What are the benzos with short half lives?
lorazepam and oxazepam (without active metabolites)
alprazolam and triazolam (with active metabolites)
benzodiazepine antagonist
flumazenil
What is an anxiolytic?
- has calming effects
- relieves anxiety
What is a hypnotic?
- promotes drowsiness
- promotes onset and maintenance of sleep
What is the chemical classification of benzos?
- basic foundation is a benzene ring fused with a diazepine ring
What is the chemical classification of barbiturates?
- all barbiturates are related to the structure of barbituric acid (thiopental, pentobarbital)
What is a GABA receptor?
- action site: GABA-A receptor
- what is GABA-A receptor
- GABA is the primary inhibitory NT in the brain
- GABA-A receptor is a hetero-oligomeric glycoprotein with 2xa, 2xB and 1xgamma subunits
- alpha subunit has 5 isoforms with alpha 1-5
- alpha 1- hypnotic
- -alpha 2-5- sedation, psychomotor effect
- GABA-A receptor is a chloride channel
- activation- chloride influx; hyperpolarizes neurons and decreases neuronal activity
How do benzos bind to the GABA-A receptors?
- enhance GABA actions - reduce excitability of neurons
- increase the frequency of channel opening events
- acts as CNS depressant
- has a low affinity for GABA-B receptors
How do barbiturates bind to the GABA-A receptor?
- bind to GABA-A receptor
- increased duration of channel opening events
- GABA mimetic at high concentrations
- inhibit glutamate AMPA receptor
What affects the onset of CNS drugs? (the time requires for drugs to be effective after administration)
- lipophilicity of drugs - affects onset of action
- why? BBB
- more lipophilic= more rapid onset of action
Duration of the effect of drugs depends on what? (duration is the amount of time that a measurable drug effect persists)
- biotransformation affects the duration of action:
- microsonal oxidation (cyt P450 isozymes: phase 1 reactions)
- conjugation (phase II reactions)
- metabolic conversion to more water soluble metabolites is required for clearance of CNS drugs from the body
Lipophilicity of BZDs?
triazolam> diazepam> lorazepam, oxazepam
Many __ metabolites of benzos are active
phase I
What is the main differences between benzos?
- the rate of onset and the duration of action
How do the therapeutic uses relate to the half lives of drugs
short acting: preferred as hypnotic
long acting: preferred as anxiolytic
Where are benzos excreted?
kidneys
Can benzos cross the placenta? Can be detected in breast milk?
yes to both
Where are benzos redistributed in obese patients?
adipose tissue
Where are barbiturates metabolized?
the liver
Barbiturates are ____ inducers
hepatic cyt P450 system
Are barbiturates lipophilic or hydrophilic?
lipophilic
What are the different duration of actions of barbiturates and what are they used for?
- ultra short acting (30 min)- thiopental for induction of anesthesia
- short acting (18-48 hrs)- secobarbital. phenobarbital for hypnotic and sedative
- long acting (4-5 days)- phenobarbital for seizures
Therapeutic used for benzos
- for relief of anxiety
- for treatment of insomnia
- for sedation and amnesia before and during surgical procedures
- for treatment of epilepsy and seizure states
- for muscle relaxation in specific neuromuscular disorder
- for control of ethanol withdrawal symptoms or other sedative hypnotic withdrawal states