The Use of Anxiolytic and Sedative Drugs Flashcards
1
Q
What are barbiturates?
Describe their use.
A
- Still used as IV induction agents in anaesthesia and as second and third line anticonvulsants.
- BUT:
- Dependence
- Addiction
- Misuse
- Narrow therapeutic index
- These are OBSOLETE as anxiolytics.
2
Q
What are the classes of drugs used for anxiety?
A
- Antidepressants
- Benzodiazepines
- Z-drugs
- Beta-blockers (blocking effects of sympathetic system)
- Other
- Melatonin
- Sedating antihistamine
3
Q
Describe the properties of benzodiazepines.
A
- Highly lipophilic
- Well absorbed orally
- Highly protein bound
- Hepatic metabolism
- Active metabolites
- Excreted as glucoronide conjugate
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4
Q
Describe the pharmacokinetics of benzodiazepines.
A
- Pharmacokinetics = what the body does to the drug.
- Well absorbed orally - peak effects 30 minutes - 2 hours.
- Highly lipophilic - absorbed fast and enter the CNS quickly.
- Highly protein bound - big reservor and tend to be long acting.
- Duration of action - redistribution. Passes out of the brain and redistributes to muslce and fat where it has little to no effect. It is not eliminated by the body but it no longer has any effect.
- Hepatic metabolism (cytochrome p450).
- Many have active metabolites.
- Renal excretion.
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5
Q
What are the 5 major effects of benzodiazepines?
A
- Anxiolytic: reduce anxiety (α2 and α3)
- Hypnotic: induce sleep (α1)
- Reduce muscle tone
- Anterograde amnesia (pros and cons)
- Anticonvulsant effect
6
Q
How are benzodiazepines administered?
A
- Normally given orally or IV
- Can be given by intranasal or rectal route
- Not advised to give IM simply because it is very painful
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7
Q
Describe GABAA receptors.
A
- Pentameric arrangement.
- Central Cl- ion channel pore.
- 18 possible sub-units.
- Approximately 30 forms of receptor.
- Some subunits location specific.
- Anaesthetics and benzos allosterically activate the receptor.
- Increase the frequency of opening.
- Act alosterically on GABAA receptors.
- Sedation mediated via GABAA with α1 subunit.
- Anxiolysis mediated via GABAA with α2 and α3 subunits.
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8
Q
What is flumazenil?
Describe its use.
A
- Competative benzodiazepine antagonist.
- Short half-life compared with benzodiazepines.
- May precipitate agitation and seizures.
- Given IV in 100µg increments.
- Side Effects:
- Nausea
- Vomiting
- Supportive management is better - let them sleep it off. If you give this and send them home, they will get sleepy again when the antagonist wears off.
9
Q
How do Z drugs work?
A
- Act via benzodiazepine receptors.
- Structurally different.
- Very similar pharmacodynamic profile.
- Examples:
- Zopiclone
- Zaleplon
- Zolpidem
10
Q
What is tolerance?
Describe tolerance with respect to benzodiazepines.
A
- Tolerance: is a physiological reaction (neuroadaptation) characterised by a decrease in the effects of a drug with chronic administration.
- Benzodiazepines:
- Tolerance develops quickly for sedative effects.
- More slowly for anxiolytic and anticonvulsant effects.
- Neuroadaptive: desensitisation of inhibitory GABA receptors.
- Sensitisation of (excitatory) NMDA receptors.
11
Q
What is dependence?
A
- 3 of these 6 criteria in the last 12 months.
- The drug induces a rewarding experience.
- Drug taking becomes compulsive.
- Psychological dependence.
- Physical dependence.
- Genetic factors.
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12
Q
Describe withdrawl from benzodiazepines.
A
- A result of physical dependence
- Increased anxiety, onset / exacerbation of depression
- Disturbed sleep
- Pain, stiffness, muscular aches
- Convulsions
- Can occur after relatively short courses of treatment (4 weeks)
13
Q
Describe the misuse of benzodiazepines.
A
- Common drug of misuse / abuse
- Usually part of polydrug misuse
- Enhances “highs”
- Attenuates “crashes”
- In part iatrogenically driven
14
Q
When will you prescribe benzodiazepines?
A
- To enable potentially uncomfortable diagnostic & therapeutic procedures to be carried out.
- Management of acute alcohol withdrawal
- Management of insomnia
- Management of generalised anxiety states
- Other: anticonvulsant
15
Q
Describe the use of benzodiazepines in the management of acute alcohol withdrawl?
A
- Acute admissions to hospital
- Supply of alcohol interrupted
- Index of suspicion
- Alcohol history
- Severity of alcohol dependence questionnaire
- Assessment of withdrawal symptoms
- Chlordiazepoxide 1-2 week reducing regime