Pharmacology of Barbiturates
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Questions and Answers

What is the effect of barbiturates on the respiratory system?

Hypoventilation and Hypoxia

What is the effect of barbiturates on the uterus?

Decreased uterine contractility, leading to post-partum hemorrhage

What is the effect of barbiturates on the liver?

Induction of Hepatic Microsomal Enzymes, leading to increased metabolism of barbiturates and other drugs

What is the effect of barbiturates on the cardiovascular system?

<p>Hypotension, particularly at large doses</p> Signup and view all the answers

What is the effect of barbiturates on analgesia?

<p>Potentiation of analgesics, but can cause hyperalgesia and delirium when used alone</p> Signup and view all the answers

What is the effect of large doses of barbiturates on the central nervous system?

<p>Depression of vital medullary centers, leading to respiratory and cardiovascular depression</p> Signup and view all the answers

What is considered an 'Anxiety disorder'?

<p>Excessive anxiety that causes irrational thinking or behavior and impairs a person's functioning</p> Signup and view all the answers

Which of the following are symptoms associated with Anxiety Disorders? (Select all that apply)

<p>Physiological symptoms (e.g., tachycardia)</p> Signup and view all the answers

Genetic factors have been definitively identified as the main cause of anxiety disorders.

<p>False</p> Signup and view all the answers

Patients experiencing one or more negative life events have a _____ increased chance of developing Generalized Anxiety Disorder (GAD) or Panic Disorder (PD).

<p>3-fold</p> Signup and view all the answers

Match the following medications with their use in treating anxiety disorders:

<p>Buspirone = Partial agonist of 5-HT1A receptors Hydroxyzine = Reduction in serotonin levels Antidepressants = Pharmacological therapy for anxiety disorders Benzodiazepines = Short-term management of acute anxiety symptoms</p> Signup and view all the answers

What is the most extensively studied benzodiazepine for the treatment of Social Anxiety Disorder (SAD)?

<p>Clonazepam</p> Signup and view all the answers

Why is Clonazepam not desirable for long-term treatment of SAD?

<p>All of the above</p> Signup and view all the answers

Patients with Social Anxiety Disorder generally respond rapidly to treatment.

<p>False</p> Signup and view all the answers

Long use of benzodiazepines more than a week results in tolerance mainly to the _ effect.

<p>sedative</p> Signup and view all the answers

Match the following effects with benzodiazepines:

<p>Anxiety treatment = Clonazepam Anti-Convulsant &amp; Anti-Epileptic = Diazepam &amp; Clonazepam Daytime sedation or Anxiety = Short-acting Benzodiazepines Anterograde Amnesia = Triazolam</p> Signup and view all the answers

Define the term 'Sedatives' and 'Hypnotics'.

<p>Sedatives are drugs that calm behavior but produce drowsiness. Hypnotics are drugs that induce or maintain a state like sleep.</p> Signup and view all the answers

What is the difference in effect between a small dose of Sedative and a large dose of Hypnotic?

<p>Small dose causes drowsiness, large dose induces sleep</p> Signup and view all the answers

Barbiturates mainly affect the Cortex and Reticular Activating System.

<p>True</p> Signup and view all the answers

GABA-A transmission facilitated by Barbiturates results in increased ______ influx.

<p>Cl-</p> Signup and view all the answers

Match the following statements with the correct term: 1- Drugs that calm behavior but produce drowsiness 2- Drugs that induce or maintain a state like sleep 3- Classification of Barbiturates 4- Mechanism of Action of Barbiturates

<p>Sedatives = Hypnotics</p> Signup and view all the answers

Study Notes

Actions of Barbiturates on the CNS

  • Sedative action that leads to drowsiness
  • Hypnotic action that causes abnormal sleep, leading to hang-over and rebound paradoxical sleep after tolerance or stopping the drug
  • Cause amnesia
  • Can induce general anesthesia, especially with ultra-short acting barbiturates
  • Act as anti-convulsants, treating all types of convulsions (all barbiturates), while phenobarbital specifically treats Grand Mal epilepsy but worsens Petit mal epilepsy

Effects on Vital Centers

  • Large doses can suppress respiratory centers, leading to hypoventilation and hypoxia
  • Can suppress vasomotor centers, leading to hypotension
  • Affect heat regulating centers, causing hypothermia

Other Effects of Barbiturates

Cardiovascular System

  • Therapeutic doses have minimal effects
  • Large doses cause hypotension due to suppression of vasomotor centers, heart, and vasodilation

Respiratory System

  • Large doses cause hypoventilation and hypoxia

Gastrointestinal Tract

  • Cause hypomotility and hyposecretion

Kidneys

  • Cause oliguria due to suppression of blood pressure and antidiuretic hormone

Hormonal Effects

  • Suppress antidiuretic hormone and adrenocorticotropic hormone

Uterus

  • Suppress uterine contractility, leading to post-partum hemorrhage, and can pass the placental barrier, causing neonatal asphyxia

Skeletal Muscle

  • Large doses cause mild relaxation

Liver

  • Barbiturates induce hepatic microsomal enzymes, leading to increased metabolism of the drug itself, resulting in tolerance and cross-tolerance
  • Affect the metabolism of other drugs, leading to drug interactions

CNS Depressants

  • CNS Depressants: sedatives and hypnotics
  • Sedatives: calm behavior, produce drowsiness
  • Hypnotics: induce or maintain a state like sleep
  • Small dose: sedation, large dose: hypnosis
  • Reticular Activating System (RAS): responsible for alertness and wakefulness
  • Barbiturates: non-selective CNS depressants, interact with GABA-A receptors, leading to hyperpolarization and post-synaptic inhibition

Barbiturates

  • Classification:
    • Long-acting (e.g. phenobarbital)
    • Intermediate-acting (e.g. amobarbital)
    • Short-acting (e.g. pentobarbital)
    • Ultra-short acting (e.g. thiopentone)
  • Mechanism of Action:
    • Stimulate specific barbiturate receptors
    • Facilitate GABA-A transmission
    • Increase Cl- influx, leading to hyperpolarization and post-synaptic inhibition
  • Actions:
    • Sedative and hypnotic effects
    • Anticonvulsant and anti-epileptic effects (phenobarbital)
    • Anesthetic effects (ultra-short acting barbiturates)
  • Adverse Effects:
    • Idiosyncrasy (acute porphyria)
    • Induction of hepatic microsomal enzymes, leading to tolerance and drug interactions
    • Dependence and addiction
    • Respiratory depression and hypoventilation

Benzodiazepines (Bz)

  • Pharmacokinetics:
    • Well absorbed orally
    • Highly bound to plasma proteins
    • Metabolized by hepatic microsomal enzymes
    • Excreted renally
  • Mechanism of Action:
    • Bind to specific Bz receptors (Bz1 and Bz2)
    • Activate GABA-A transmission
    • Increase Cl- influx, leading to hyperpolarization and post-synaptic inhibition
  • Actions:
    • Anxiolytic (anti-anxiety) effects
    • Sedative and hypnotic effects
    • Muscle relaxant effects
    • Anticonvulsant effects
  • Adverse Effects:
    • Dependence and addiction
    • Withdrawal symptoms
    • Interactions with other drugs
    • Respiratory depression and hypoventilation

Anxiety and Anxiety Disorders

  • Anxiety: a normal response to stressful or fearful situations

  • Anxiety Disorders:

    • Generalized Anxiety Disorder (GAD)
    • Panic Disorder (PD)
    • Social Anxiety Disorder (SAD)
    • Post-Traumatic Stress Disorder (PTSD)

  • Treatment:

    • Benzodiazepines (short-term management of acute anxiety symptoms)
    • Antidepressants (long-term management of anxiety disorders)
    • Buspirone (non-benzodiazepine anxiolytic)
    • Hydroxyzine (5-HT2A receptor antagonist)
    • Psychotherapy (cognitive-behavioral therapy)### Panic Disorder (PD)

  • A panic attack typically lasts 20-30 minutes, with peak intensity within the first 10 minutes.

  • Common symptoms include anxiety about being in places or situations where escape might be difficult or help might not be available.

  • Agoraphobia often develops secondary to panic attacks, where patients avoid specific situations due to fear of a panic attack.

Treatment of PD

  • Pharmacological therapy: Antidepressants (TCAs, SSRIs, SNRIs, MAOIs), Benzodiazepines
  • Non-pharmacological therapy: Psychoeducation, Cognitive-behavioral therapy (CBT), Avoid stimulants
  • Patients with PD experience greater rebound anxiety and relapse when discontinuing benzodiazepines than GAD patients.

Social Anxiety Disorder (SAD)

  • Fear of social or performance situations in which the person is exposed to possible scrutiny by others.
  • Physical symptoms include blushing, diarrhea, sweating, tachycardia, and trembling.

Treatment of SAD

  • Pharmacological therapy: Antidepressants, Benzodiazepines (Clonazepam)
  • Non-pharmacological therapy: Cognitive-behavioral therapy (CBT), Psychotherapy
  • Patients with SAD generally respond slowly to treatment, and many will not achieve a full response.

Benzodiazepines (Bz)

  • Classification: Hypnotic, Anxiolytic, Anticonvulsant, Skeletal muscle relaxant, Antidepressant
  • Mechanism of action: Enhance GABA transmission, bind to GABA receptors
  • Pharmacological actions: Anxiolytic, Sedative-hypnotic, Anticonvulsant, Skeletal muscle relaxant, Antidepressant

Adverse Effects of Bz

  • Dependence and addiction
  • Daytime sedation, anxiety, and rebound anxiety
  • Affect mental, psycho-motor, and sexual functions
  • Anterograde amnesia, especially with Triazolam
  • Aged patients: mental confusion, hypotension
  • Additive effects with alcohol, ataxia, and teratogenic effects

Barbiturates vs. Benzodiazepines

  • Barbiturates: Marked suppression of REM sleep, tolerance, and dependence, low therapeutic index
  • Benzodiazepines: Less suppression of REM sleep, less tolerance and dependence, high therapeutic index

Non-Benzodiazepines (Z-Drugs)

  • Zolpidem and Zopiclone: GABA-A receptor agonists, hypnotics with minimal REM suppression, minimal muscle relaxation or anticonvulsant effect
  • Minimal tolerance and dependence, short-acting

Flumazenil (Anexate)

  • Selective and competitive block of Bz-receptors, antagonizes ALL actions of Bz
  • Used to treat benzodiazepine overdose, extensive hepatic first-pass metabolism, short half-life

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Description

This quiz covers the effects of barbiturates on the central nervous system, including sedative, hypnotic, amnesic, anesthetic, and anticonvulsant actions. Learn about the different effects of barbiturates on the CNS and their pharmacological uses.

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