17. Anxiolytics Flashcards
General role of anxiolytic
alleviate fear and anxiety
General role of sedatives
- alleviate fear and anxiety
- produce a degree of amnesia and analgesia
General role of hypnotics
induce sleep
Why do dentists need to know about anxiolytics-sedative-hypnotic drugs?
- administered to patients who can’t handle emotional stress of the dentists
- like in anxiety (feeling uneasy, palpitations, sweating, tense muscles, headache)
- some patients may need sedation
What does the GDC think about conscious sedation?
- can be effective method of facilitating dental treatment
- produces a state of depression of the CNS
- verbal contact with patient is maintained
- deep sedation … must be regarded as general anaesthesia
- patient … is able to understand and respond to verbal commands
3 methods of administration in dentistry and what sedatives are admitted like this
- inhalation - nitrous oxide
- oral - benzodiazepines and H1 antagonists
- intravenous - benzodiazepines
What must be used alongside a sedative?
- local anaesthesia
- sedation alone can’t effectievly control pain
Difference in sedation and anaesthesia
- degree of unconsciousness
Explain effect of nitrous oxide
- light and rapid anaesthesia
- 50% NO in oxygen - entonox
- recovery in around 4 minutes
- mild nausea and vomiting
Negatives to nitrous oxide
- expensive
- limited patient groups (COPD)
- prolonged or repeated exposure causes changes to bone marrow and teratogenic risk
How is sedative effect dose dependent?
- relief of anxiety
- sedation
- hypnosis
- general anaesthesia
What is a barbiturate?
- positive allosteric modulator of GABAa receptors
- distinct binding site of benzodiazepines
What do barbiturates do?
- direct effect on ion channel gating/opening
- increase effects of GABA and inhibit glutamate neurotransmission
- clinical use limited by increased toxicity in overdose
3 types of anxiety disorders
- panic disorder
- generalised anxiety disorder
- simple phobia
What is panic disorder?
discrete periods of intense fear
What is generalised anxiety disorder?
chronic worry
What is simple phobia?
fear of object or situation
What treats anxiety disorders?
benzodiazepines
Pharmacological effects of benzodiazepines
- reduction of anxiety and aggression
- sedation and induction of sleep
- muscle relaxation
- anticonvulsant effects
- amnesia
How do benzodiazepines sedate and induce sleep?
- decrease time taken to get to sleep
- increase total duration of sleep
- decrease REM sleep (dreaming)
- decrease SW sleep (deep sleep)
How do benzodiazepines cause muscle relaxation?
- increased muscle tone usually in anxious people
- may cause aches and pains like headache
- relaxant effect so clinically useful
Mode of action of benzodiazepines
- benzos act by binding to specific regulatory site of GABAa receptor
- this binding enhances neuronal inhibitory effect of GABA
- GABA and benzo bind to independent sites of same receptor-Cl-ion channel complex
- benzo don’t open Cl-ion channel by themselves, just increase the affinity for receptor for GABA
Pharmacokinetics of benzodiazepines
- well absorbed when given orally
- binds strongly to plasma proteins
- high lipid solubility leads to accumulation in body fat
- inactivated by metabolism and excreted as glucoronides in urine
- varys on action length
Why are some benzos short acting?
- metabolised to inactive compounds
- short half life e.g temazepam
Why are some benzos long acting?
- metabolised to pharmacologically active metabolites with long half lives
- diazepam is metabolised to noridazepam which has a half life of around 60 hrs for example
Which benzo goes straight to glucuronide?
lorazepam
Which benzos become hydroxylated metabolites before glucuronide?
- triazolam
- alprazolam
- midrazolam
- clonazepam
Unwanted effects of benzos
- interacts with alcohol
- long lasting ‘hangover effects’ e.g drowsiness, confusion
- development of dependence
- sexual fantasies
Why can benzos be used in suicide attempters?
- reasonably safe in overdose
How do benzos act in dentistry?
- ensure undisturbed sleep before a dental appointment
- sedation as adjunct to local anaesthesia - amnesia
- pre-anaesthetic medication (anti-anxiolytic)
What do beta-adrenoceptor antagonists do?
- anxiolytic but not sedative - reduce physcial symptoms like tremor, palpitations
- inhibit somatic or autonomic responses - decreases noradrenergic transmission
Example of a beta-adrenoreceptor antagonist
- propranolol
Unwanted side effects of beta-adrenoceptor antagonists
- cardiac depression, bradycardia
- non-selective beta-adrenoceptor inhibition (beta1/beta 2)
What do 5-HT1a agonists do ?
- anxiolytic but not sedative - partial agonist of inhibitory autoreceptors (5-HT1A)
- long anxiolytic development time - over 2 weeks
Example of a 5-HT1a agonist
buspirone
Do 5-HT1a agonists have lots of withdrawal effects?
- no
- generally mild nausea and dizziness but not much
