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Benzodiazepines

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Benzodiazepines
Selective CNS depressants that bind to the BZ binding site on the GABAa receptor on the alpha subunit
GABA binding site
Beta subunit of GABA gated receptors is where this binds
alpha-1 subunit functions
anticonvulsive and and sedative-hypnotic actions
alpha-2 subunit functions
anxiolytic actions
alpha-5 subunit functions
memory impairment
Diazepam binds to these subunits
BZ that binds to a1,2,3, and 5
Zolpidem binds to these subunits
Binds more selectively to alpha-1 subunit
B-carbolines
these are inverse agonists at the BZ receptor that negatively modulate GABA function and oppose BZ action
Flumazenil
BZ antagonist used to reverse BZ actions.

Short half life
Ramelteon
Melatonin receptor agonist with hypnotic actions and lower abuse liablity.

Used for delayed sleep phase syndrome

Actions mediated by MT1 andMT2 receptors in the suprachiasmatic nucleus where the circadian pacemaker is located

CYP1A2 oxidation
-fluvoxamine (antidepressant) increase half life 190fold
-rifampin decrease serum levals via CYP1A2 activation

Affect hormone levels and is contraindicated in pubescent/ prepubescent patients and pregnancy
Busipirone
5ht partial agonist structurally unrelated to BZs used for general anxiety disorder due to gradual onset.

No anticonvulsant or hypnotic actions and minimal sedation or psychomotor impairment

Takes 1-3 weeks to take action and is rapidly absoprbed and undergoes extensive first pass metabolism

Can cause pupillary constriction, anti-cholinergic symptoms, and hypertension(when used with MAOI)
5 functions of Benzodiazepines
1.Anxiolytic
2. Hypnotic- idiopathic or behavioral (not in sleep apnea)
3. Anticonvulsant- status epilepticus, absence seizures
4. Preanesthetic
5. Muscle relaxant- suppreses reticular system (doesn't work at nmj)
Sedative and anticonvulsant actions*
Tolerance develops most for these two actions of BZs (*more slowly, clonazepam resistant)
Difference from Non-selective CNS depressants
BZ structure determines their actions at the GABAa receptor
(as opposed to lipophillic nature
Biotransformed in the liver via oxidation or conjugation
Benzodiazepines metabolism