Anxiolytics

  • Created by: LBCW0502
  • Created on: 23-10-18 18:41
What is anxiety?
One of the most frequent human emotions. It is associated with the perception or anticipation of a danger threatening the integrity, security, well-being and self-esteem of the individual
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What is normal anxiety?
A stressful situation, for example before an exam or an interview, or during a worrying time such as illness.
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What is pathological anxiety?
Very prolonged and severe occurs without a stressful events and interferes with normal life. Associated with illness (thyroid disorders) or depression or personality disorders. Clinical conditions - phobic anxiety, panic disorders
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What are the major manifestations of anxiety?
Somatic/autonomic effects (restless, agitation, insomnia). Psychological symptoms (irritability, insomnia, inability to concentrate) - Neural circuitry involving amygdala and hippocampus - thought to underlie anxiety (limbic system)
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Which part of the brain is most specifically involved with emotional experience?
Amygdala. Pathological anxiety conceptualised as exaggerated fear, hyperexcitability, expressed as hypervigilance and increased behavioural responsivity to fearful stimuli
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Describe features of pre-clinical testing
Anxiety is a particular form of behavioural inhibition that occurs is response to events that are novel, non-rewarding or punishing. Two tests - animal in transparent box with bottle initiating electric shock, elevated maze with 2 open/2 closed arms
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What were the results for the subject treated with diazepam compared to the control?
Subject treated with diazepam should lower levels of anxiety e.g. drinking more water from bottle despite electric shock, subject remains in open areas for longer
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Describe features of anxiolytic drugs (1)
Benzodiazepines, 5-HT 1A receptor agonists (buspirone). Barbiturates - largely obsolete. B-adrenergic antagonists - propranolol (some forms of anxiety where physical symptoms e.g. tachycardia are troublesome
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Describe features of anxiolytic drugs (2)
Miscellaneous other drugs - chloral hydrate, meprobamate and paraldehyde (mainly used in hospitals)
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Describe features of benzodiazepines
Different durations of actions, different half lives, different uses (e.g. hypnotic, muscle relaxant, anxiolytic)
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What are the pharmacological effects of benzodiazipines? (1)
Reduction of anxiety/aggression (anxiolytic). Sedation/induction of sleep (sedative/hypnotic). Reduction of muscle tone and co-ordination (muscle relaxant). Anticonvulsant effect
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What are the pharmacological effects of benzodiazipines? (2)
Most BDZ have sedative effects, no antidepressant effects except alprazolam
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Describe features of anxiolytic effects (1)
Anxiety/panic disorders (chronic illnesses). Chlordiazepoxide (60s). Diazepam widely used: longer half life, multiple doses results in accumulation of diazepam/desmethyldiazepam in adipose tissue
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Describe features of anxiolytic effects (2)
Alprazolam: short half life (10-24h), less likely to accumulate and to cause cumulative sedation when multiple daily doses are taken
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Describe features of hypnotic effects (1)
BDZ decrease time taken to get to sleep and increase total duration of sleep. BDZ affect the REM sleep less than other hypnotic. Proportion of slow wave sleep is reduced through growth hormone secretion is unaffected
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Describe features of hypnotic effects (2)
Patients suffer from withdrawal symptoms when treatment is removed (sleep becomes worse than before starting treatment). BDZ does not effect growth hormone secretion (barbiturates affect growth hormone secretion)
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Describe features of muscle relaxant effects
BDZ reduce muscle tone by central action/independent on sedative effect. Reduction of muscle tone produced without appreciable loss of coordination. Increased muscle tone/common feature of anxiety. Relaxant effect of BDZ clinically useful
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Describe anticonvulsant effects of benzodiazepines
All of the BDZ have anticonvulsant activity in pre-clinical tests. Clonazepam is used as anti-epileptic. Diazepam given as IV is used to treat status epilepticus. Most BDZ are not used as maintenance anti-epileptic therapy because of sedative effect
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Describe the mechanism of action of benzodiazepams (1)
BDZ act selectively on GABA-A receptor. They are not GABA agonists. They exert GABA-mimetic action when GABA is functional
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Describe the mechanism of action of benzodiazepams (2)
GABA-A receptor can be in conformation A where BDZ and GABA bind to allow ion channel to open/Cl influx. GABA-A receptor can be in conformation B were B-carbolin binds as an inverse agonist (no efficacy)
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Give an example of a benzodiazepine antagonist
Flumazenil - can bind to both A and B conformations of GABA-A receptor
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Describe the pharmacokinetics of benzodiazepines
BDZ well absorbed when given orally. Peak plasma concentration in about 1h. Strong plasma protein binding. Lipid soluble, accumulate in body fat. Metabolised and excreted in the urine as glucuronides. BDZ vary greatly in duration of action
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What are the undesired effects of benzodiazepines?
Acute overdosage - toxic effects. Side effects during therapeutic use. Tolerance and dependence
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Describe features of acute toxicity
BDZ overdose causes prolonged sleep without serious depression of respiration or cardiovascular function. BDZ and alcohol can cause severe respiratory depression. BDZ overdose can be treated with flumazenil (risk of seizures)
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What are the side effects during therapeutic use?
Drowsiness, confusion, amnesia and impaired co-ordination. Interaction with alcohol. When used as hypnotic, BDZ can cause day-after impairment of job performance and driving skills
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Describe features of tolerance and dependence
All BDZ induce physical dependence which is the main drawback. Stopping BDZ treatment causes anxiety, tremor and dizziness. Severe psychological dependence is not a major problem
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Describe features of Buspirone
Potent 5HT1A receptor agonist. May act on inhibitory pre-synaptic receptors thereby inhibiting serotonin release. Takes days/weeks to show efficacy in man. Ineffective in controlling panic attacks. Side effects - nausea, dizziness, headache, restless
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Describe features of barbiturates (1)
Hypnotics/sedatives. Barbiturates have depressant activity on CNS. Cause death from respiratory/cardiovascular depression in large doses. Pentobarbitone (hypnotic/anxiolytic). Phenobarbitone (anticonvulsant). Thiopentone (anaesthetic/IV)
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Describe features of barbiturates (2)
Enhance action of GABA but are less specific than BDZ. Induce tolerance, dependence and increase metabolic degradation of other drugs
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Card 2

Front

What is normal anxiety?

Back

A stressful situation, for example before an exam or an interview, or during a worrying time such as illness.

Card 3

Front

What is pathological anxiety?

Back

Preview of the front of card 3

Card 4

Front

What are the major manifestations of anxiety?

Back

Preview of the front of card 4

Card 5

Front

Which part of the brain is most specifically involved with emotional experience?

Back

Preview of the front of card 5
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