4. Hypnotics, Anesthetics, Blocks Flashcards
(37 cards)
Barbiturates - Available Drugs
- Phenobarbital
- Pentobarbital
- Thiopental
- Secobarbital
Barbiturates - MOA
- Facilitate GABAa action by increasing duration of Cl channel opening and thereby decreasing neuron firing (Benzos, Barbiturates, and EtOH all bind GABAa receptor which is a ligand gated Cl channel)
“BarbiDURATe = increase Cl channel DURATion”
[Phenobarbital, Pentobarbital, Thiopental, Secobarbital]
Barbiturates - Clinical Use
(1st linen children)
- Simple partial seizures (Phenobarbital)
- Complex partial seizures (Phenobarbital)
- Tonic-clonic seizures (Phenobarbital)
- Sedative for anxiety
- Insomnia
- Induction of anesthesia (Thiopental)
[Phenobarbital, Pentobarbital, Thiopental, Secobarbital]
Barbiturates - Toxicities
- Dependence
- Additive CNS depression with alcohol (Benzos, Barbiturates, and EtOH all bind GABAa receptor which is a ligand gated Cl channel)
- Respiratory or Cardiac depression - can be fatal
- p450 induction
- CI in porphyria
- Overdose treated symptomatically
- —- Assist respiration, Increase BP[Phenobarbital, Pentobarbital, Thiopental, Secobarbital]
Benzodiazepines - Available Drugs
- Diazepam
- Lorazepam
- Triazolam
- Temazepam
- Oxazepam
- Midazolam
- Chlordiazepoxide
- Alprazolam
Benzodiazepines - MOA
- Facilitate GABAa action by increasing FREQUENCY of Cl channel opening (Benzos, Barbiturates, and EtOH all bind GABAa receptor which is a ligand gated Cl channel)
- Decrease REM sleep - Most have long half lives and active metabolites
“FREnzodiazepines = Increase Cl channel FREquency”
“SHORT acting - TOM thumb = Triazolam, Oxazepam, Midazolam” (highest addiction potential)
[Diazepam, Lorazepam, Triazolam, Temazepam, Oxazepam, Midazolam, Chordiazepoxide, Alprazolam]
Benzodiazepines - Clinical Use
- 1st line for acute status epilepticus (Lorazepam, Diazepam)
- Seizures of eclampsia (Lorazepam, Diazepam)
- Anxiety
- Spasticity
- Detoxification especially EtOH withdrawal DT’s
- Night terrors
- Sleepwalking
- General anesthetic (Amnesia, muscle relaxation)
- Hypnotic (insomnia)
[Diazepam, Lorazepam, Triazolam, Temazepam, Oxazepam, Midazolam, Chordiazepoxide, Alprazolam]
Benzodiazepines - Toxicities
- Dependence
- Additive CNS depression with EtOH (Benzos, Barbiturates, and EtOH all bind GABAa receptor which is a ligand gated Cl channel)
- Less risk of respiratory depression and coma than with barbiturates
- Treat overdose with Flumazenil (competitive antagonist at GABA benzodiazepine receptor)
[Diazepam, Lorazepam, Triazolam, Temazepam, Oxazepam, Midazolam, Chordiazepoxide, Alprazolam]
Non-Benzo Hypnotics - Available Drugs
- Zolpidem (Ambien)
- Zaleplon
- Eszopiclone
“Catch some Z’s”
Non-Benzo Hypnotics - MOA
Act via the BZ1 receptor subtype and are reversed by flumazenil
- Zolpidem (Ambien)
- Zaleplon
- Eszopiclone
Non-Benzo Hypnotics - Clinical Use
Insomnia
- Zolpidem (Ambien)
- Zaleplon
- Eszopiclone
Non-Benzo Hypnotics - Toxicities
- Ataxia, headaches, confusion
- Short duration of side effects due to rapid metabolism by liver enzymes
- Unlike older sedative hypnotics these cause only modest day after psychomotor depression and few amnetic effects
- Lower dependence risk than Benzos
- Zolpidem (Ambien)
- Zaleplon
- Eszopiclone
General Principles of Anesthetics
- CNS drugs must be lipid soluble to cross the BBB or be actively transported
- Drugs with low blood solubility have rapid induction and recovery times. Drugs with high blood solubtility = high blood/gas partition coefficient = Increaed solubility = Increasd gas required to saturate the blood = slower onset of action
- MAC = Minimal alveolar concentration at which 50% of the population is anesthatized
- Drugs with higher lipid solubility = Increased potency = 1/MAC
N2O has low blood and lipid solubility –> fast induction / Low potency
Halothane has high blood and lipid solubility –> Slow induction / High potency
- Increasing rate and depth of ventilation will increase gas tension
- Increased AV concentration gradient = Increased tissue solubility = Increased gas required to saturate tissue = Slower onset of action
Inhaled Anesthetics - Available Drugs
- Halothane
- Enflurane
- Isoflurane
- Sevoflurane
- Methoxyflurane
- NO
Inhaled Anesthetics - MOA
Unknown
Effects:
- Myocardial depression
- Respiratory depression
- Nausea/emesis
- Increased cerebral blood flow (decreased cerebral metabolic demand
(Halothane, Enflurane, Isoflurane, SEvoflurane, Methoxyflurane, NO)
Inhaled Anesthetics - Clinical Use
Anesthesia
(Halothane, Enflurane, Isoflurane, SEvoflurane, Methoxyflurane, NO)
Inhaled Anesthetics - Toxicities
- Malignant Hyperthermia (except NO)
- Halothane - Hepatotoxicity
- Methoxyflurane - Nephrotoxicity
- Enflurane - Proconvulsant
- NO - Expansion of trapped gas
(Halothane, Enflurane, Isoflurane, SEvoflurane, Methoxyflurane, NO)
IV Anesthetics - Available Drugs
- Barbiturates
- Benzodiazepines
- Arylcyclohexylamines (Ketamine)
- Opiates
- Propofol
“BB King on OPIATES PROPOses FOOLishly”
Barbiturate Anesthetic Effect
Tiopental
- High lipid solubility –> Rapid entry into the brain –> High potency
- Used for induction of anesthesia and short surgical procedures
- Effect terminated by rapid redistribution into tissure, ie skeletal muscle, and fat
- Decreases cerebral blood flow
Benzodiazepines Anesthetic Effect
- Midazolam most commonly used for endoscopy - used adjunctively with gaseous anesthetics and narcotics
- May cause severe postoperative respiratory depression, decreased BP (treat overdose with Flumazenil), and amnesia
Arylcyclohexylamines Anesthetic Effect
Ketamine
- Block NMDA receptor
- Cardiovascular stimulant
- Cause disorientation, hallucinations, and bad dreams
- Increae cerebral blood flow
Opiate Anesthetic Effects
Morphine and Fentanyl used with other CNS depressants during general anesthesia
Propofol Anesthetic Effects
- Used for rapid anesthesia induction and short procedures
- Less postoperative nausea than Thiopental
- Potentiates GABAa
Local Anesthetics - Available Drugs
Esters
- Procaine
- Cocaine
- Tetracaine
Amides
- Lidocaine
- Meplivacaine
- Bupivacaine
“amIdes have 2 I’s in their names”
