Pharm Flashcards
Describe “context-sensitive half time”
Context-sensitive half-time often cannot be predicted by the elimination half-life when a drug is continuously infused (vs administered via single bolus).
Distribution of the drug and accumulation in tissues results in a longer half-life of drugs administered via continuous infusion.
With these drugs, it is important to occasionally rouse patient to assess CNS function.
What are examples of drugs that are more severely affected by context-sensitive half times, and an example of a drug that is not? What does this mean?
Fentanyl and benzodiazepines are significantly affected by their context-sensitive half-time; their half-lives are increased dramatically, and it is especially important to monitor patients’ CNS function during continuous infusion.
Propofol is not especially affected by its context-sensitive half-time; with both bolus and continuous infusions, patients wake quickly (half-life is not dramatically extended during continuous infusion).
Name some sedative/anesthetic drugs that work via GABA receptors
Barbituates
Propofol
Etomidate
Benzodiazepines
Name a sedative/anesthetic that works via glutamate receptors
Ketamine
Describe the MOA of and indications for benzodiazepines
Benzos work via modulation of GABA receptors. They do NOT directly bind GABA receptor sites - they bind allosterically to potentiate GABA’s effect. More Cl- flows through channels and GABA’s inhibitory effect is increased.
These are used perioperatively (for anterograde amnesia, anxiolysis, and induction), sedation/hypnosis, seizure control, and ICU sedation
Describe the MOA of and indications for barbituates
Effect GABA receptors (not emphasized in lecture)
Barbituates are potent anticonvulsants. These are used for induction, but are largely being replaced by propofol. They provide no analgesia.
Describe the MOA of and indications for propofol
Propofol acts on the GABA receptor to increase its binding affinity, increasing GABA-mediated inhibition.
It is indicated for use as a sedative/anxiolytic agent; can be used as an antipruritic, and as an antiemetic agent as subanesthetic doses. It is used in induction.
Describe the MOA of and indications for etomidate
Etomidate enhances the effects of GABA by binding a subunit and opening more Cl- channels, increasing inhibitory effects.
It is a short-acting hypnotic, indicated for use in induction (in conjunction with BZs), and used in cases of CV risk or neurosurgery. It does not provide analgesia.
Name a sedative/anesthetic that works on a-adrenergic receptors
Dexmedetomidine
Describe the MOA of and indications for ketamine
Ketamine inhibits the NDMA receptor complex at the glutamate receptor
It is indicated for analgesia at subanesthetic doses; as an anesthetic, it provides analgesia, amnesia, and unconsciousness
Often used in conjuction with BZs in emergent/trauma situations, and used in induction
Describe the MOA of and indications for dexmedetomidine
Dexmedetomidine is an a2-adrenergic agonist (2a and 2b, specifically)
It is indicated for analgesia and sedation (especially in ICU) but does not provide amnesia
What drug is used to block the effects of benzos? What’s an important characteristic of this drug?
Flumazenil - competitive antagonist to benzos.
Important to remember that flumazenil does not increase elimination of benzos and it has a shorter half life; if flumazenil is administered because benzos have caused respiratory distress/arrest, it’s important to intubate/be ready for respiratory depression as the flumazenil is redistributed.
Describe the administration of benzodiazepines
Midazolam is the MC used: can be used PO, IV for induction or IM (peak effect 30-90 minutes)
Diazepam is available PO (also available as lollipop/syrup for pediatrics)
Lorazepam can be used PO or IM
Describe the onset of benzoidazepines
In general, benzos have a slower onset than most other agents
Of the benzos, IV midazolam has the fastest onset (~3 minutes)
What is significant about the duration of action and metabolism of benzos?
They are the shortest of the drugs we discussed: 3-10 minutes. They undergo rapid redistribution to the tissues.
Midazolam and diazepam undergo hepatic metabolism to produce active metabolites –> renal elimination, which may be a consideration in patients with low GFR.
Lorazepam does not produce active metabolites.
Describe the effects and drawbacks of benzos.
Provide sedation and amnesia, incld ICU sedation
\+ Minimal CV effects \+ Minimal respiratory depression \+ Produce retrograde amnesia \+ Reduce anxiety \+ Anti-convulsant \+ Can minimize fasciculations
- Does NOT provide analgesia
Rarely used alone (short duration and lack of analgesia) but can be used to balance the CV/respiratory impact of other drugs
Which anesthetic class has the shortest duration of action?
Benzodiazepines (3-10 minutes)
Name the barbituate drugs we discussed
Methohexital (MC) and thiopental (not used)
What are important characteristics of proprofol that impact its administration?
Propofol is not water soluble, so it is delivered as a 10% lipid emulsion. The egg component of the emulsion can promote bacterial growth, so preservatives are needed and it is imperative that sterile technique and use within proper time frame is observed.
Long-term use is not appropriate for this reason.
Describe the effects and drawbacks of propofol.
Anesthetic and anticonvulsant
- REDUCES BP
- Dose-related RESPIRATORY DEPRESSION
Other effects: \+ Anti-convulsant \+ Anti-pruritus \+ Anxiolytic \+ Anti-emetic \+ Safe in pregnancy \+ Rapid awakening
- No muscle relaxation
- Hypertriglyceridemia –> pancreatitis when used >48 hours
- Pain with injection
Describe the effects and drawbacks of etomidate
Management of delirium
+ MINIMAL decline in SVR (good for high-risk CV pts)
- Suppresses synthesis of cortisol = DO NOT USE for ICU sedation (inhibits 11-B-hydroxylase)
- Fasciculations/hypertonus/myoclonus
- N/V
- No analgesia
Describe the effects and drawbacks of ketamine
Dissociative anesthesia
+ Minimal respiratory depression
+ Can act as bronchodilator
+ Analgesia (instant, lasts ~40 min)
+ Amnesia (instant, lasts ~40 min)
- INCREASES HR, BP, CO via inhibition of NE re-uptake
- Emergence reactions: delirium, excitation, confusion, euphoria, fear, hallucinations (minimize with benzos)
- Increased salivary/trachiobronchial secretions
- Increased muscle tone (spec uterine muscle contraction)
What is the indication for use of fospropofol?
Moderate IV sedation (monitored anesthesia care)
Describe the onset and duration of ketamine
Onset: 15-30 seconds
Dissociative anesthetic effects last ~10-15 minutes
Analgesia/amnesia effects last ~40 minutes
Describe the effects and drawbacks of dexmedetomidine
Sedation
+ Analgesia
+ Little respiratory depression
+ Immediate rouse to consciousness
+ Can be used for ICU sedation
- No amnesia
- CV effects: hypotension, bradycardia
- Withdrawal effects when used >24 hours
What was the emphasized recommendation for pharmacologic sedation?
Use propofol or dexmedetomidine for sedation instead of benzos
What was the emphasized recommendation for prevention/treatment of delirium?
Don’t use haloperidol or atypical antipsychotics to prevent or treat delirium
(dexmedetomidine can be used in certain patients)