Pharmacology of benzodiazepines Flashcards
What are ideal agents that we want in a drug for sedation
- Rapid onset
- Predictable
- Enough working time
- Rapid recovery
- Reduce anxiety
- Amnesia – will not remember the tx
- Affordable
If a sedation agent is given in very high dose what would this lead to
indue GA
What are ways to deliver sedation drug
- Inhalation sedation – mask is put around the nose and pt inhales the drug
- Oral – tablet – not common
- Intravenous sedation – given through injection the vein
- Intranasal sedation – drug is placed near pt’s nose and pt inhales the drug
What is the routine drugs used in sedation?
- Benzodiazepines – midazolam
- Nitrous oxide
How is NO delivered
inhalation
How can midazolam be delivered?
Intra-nasal, oral or IV
Nitrous oxide: clinical effects
- Poorly soluble in blood
- poor anaesthetic
- good analgesic so used for muscle pain and in delivering baby
- causes CNS depression
- when given in combination with oxygen it does not affect cardiovascular and respiratory efforts
- rapid metabolism
- rapid recovery
- predictable action and duration
- rapid onset
What are the side effects of NO
- very few – generally safe
- overdose – nausea, vomiting, unpleasant
- high dose – mild depression of alveolar ventilation
- chronic exposure can lead to pregnancy issues – this is why it is important to scavenge gasses
What are the pharmacodynamics of a drug?
Effects of the therapeutic and side effects
what are the pharmacokinetics of a drug
the absorption, distribution and elimination of the drug
what are the key effects of BZD
- reduces anxiety and aggression
- anticonvulsant effect
- sedation and induction of sleep
- reduces muscle tone and coordination
what can high dose of BZD lead to
high dose can lead to respiratory depression – stop them from breathing
if you keep increasing the dose of BZD you will get GA
How is the BZD drug activated
- specific BZD receptors on nerve cells within the brain
- GABA INHIBITORY NEURORECTOR which is released attaches to the postsynaptic neuron and the number of sensory messages perceived by the brain is reduced – BZD prolongs the effect of GABA
What are the disadvantages of BZD
- Respiratory depression affects all pt so need to monitor RR – it’s due to the reduction in sensitivity of chemoreceptor
- cardiovascular depression – reduces CO and BP – effects of this are minor in healthy pts as they can compensate for this using baroreceptors – in pts who are cardiovascular compromised this will be more of an issue
- drug interactions: alcohol, antihistamines, opioids and some calcium channel blockers, anti-psychotics
When and how is diazepam given
- given orally as a premed night before tx or morning of – need to have sedation training to administer this
how is temazepam administered
oral
what are the benefits of temazepam
rapid onset
What are the benefits of midazolam
- water soluble
- non-irritant
- penetrates the blood-brain barrier
- rapid onset
- rapidly metabolised in liver
How can midazolam be administered
IV, intramuscular, through the rectum, intra-nasal, buccal, sublingual
What is the dose of midazolam given
5mg in 5ml (1ml given at a time)
What factors affect midazolam
factors that affect midazolam
- age – over 60 need to be careful and no more than 5mg given
- hepatic/renal function – effects the metablosim and excretion of the drug
- cardiovascular function – they may have hypotensive episode
- respiratory function
- BMI
- Sleep apnoea
- Drug interactions
What is flumazenil used for
reverse BZD in serious complications
How does flumazenil work
- Similar shape to BZD so it blocks the BZD from reaching the receptor site
- prevents GABA from releasing
- sensory messages perceived by brain increases
when can you not use flumazenil to reverse BZD effects
if the pt is allergic to BZD
cannot use this drug for routine reversal of BZD so if pt is still a bit sleep after sedation you cannot give flumazenil to reverse the BZD because there is a risk of resedation afterwards
is flumazenil short or long acting
short
