Opioid Agonist & Antagonist Flashcards
A synthetic analog of codeine
Tramadol (Ultram)
This prodrug is helpful with pain management in patients unable to take NSAIDs
Tramadol (Ultram)
Tramadol MOA
Weak mu agonist from inhibition of NE and serotonin and presynaptic stimulation of 5-HTP release.
How does Naloxone effect Tramadol SE?
analgesia partially intact
respiratory depression reversed
Toxicity seen in Tramadol overdose is related to what?
amine uptake inhibition
Tramadol is a racemic mixture, what are the effects of the + and - enantiomers?
+ binds to mu and decreases serotonin while the - inhibits NE uptake and stimulates alpha 2 receptors
Tramadol(Ultram) half-life:
5-6h
Significant CNS SE of Tramadol
Seizures
Tramadol toxicity symptoms include:
hypotension, bradycardia, seizures, coma, rhabdomyolysis
Disadvantages of Tramadol:
Interaction with Warfarin, occurrence of serotonin syndrome, and increased risk of seizures in epileptic/high-risk patients.
Tramadol (Ultram) causes what significant GI side effects?
High incidence of N/V
Why is PO use of meperidine limited?
Significant first-pass effect
Meperidine interacts with which class of drugs, and how do the SE present?
MAOIs; respiratory depression, excitation, and delirium
How does Meperidine toxicity present, and what is the cause?
Active metabolite Normeperidine leads to CNS excitation and seizures.
Use of Meperidine (Demerol) in anesthesia:
postop shivering
The potency of meperidine to morphine:
Meperidine has 1/10 the potency of morphine.
What SE occur if Meperidine is given in high enough doses?
negative inotropic and histamine release
What are these symptoms reflective of? Autonomic instability with hypertension, tachycardia, diaphoresis, hyperthermia, behavioral changes including confusion and agitation, and neuromuscular changes manifesting as hyperreflexia
Serotonin Syndrome
Severe Serotonin Syndrome symptoms include:
Coma, seizures, coagulopathy, and metabolic acidosis
Which medications place patients at increased risk of Serotonin Syndrome?
Those on medication including MAOIs, Fluoxetine, and other antidepressants.
Meperidine receptor activity:
Mu & Kappa agonist
Fentanyl receptor activity:
Mu antagonist
Fentanyl v. morphine potency:
Fentanyl 100x more potent than morphine.
After high doses of fentanyl, dopaminergic stimulation in the corpus striatum may lead to what SE?
Muscle rigidity
This accounts for the rapid onset and duration of fentanyl:
high lipid solubility
Fentanyl peak effect:
3-5m
Fentanyl Vd
4L/kg
What happens when fentanyl doses exceed 20mcg/kg?
Redistribution is insufficient to drop plasma levels as fentanyl sequesters itself in the lungs.
Fentanyl induction dose:
1-2mcg/kg
Fentanyl metabolism:
Lungs (75%) & Liver (phase 1)
Which opioid requires reduced doses of benzos, propofol, or IA with induction:
Fentanyl (Sublimaze)
Pros of sole fentanyl use in anesthesia
lacks cardiac depressant and histamine effects, and also suppresses stress
Cons to sole fentanyl use in anesthesia:
fails to blunt SNS, awareness, ventilatory depression
Compare the potency of sufentanil to both fentanyl and morphine:
Sufentanil is 1000x more potent than morphine and 100x more potent than fentanyl.
Sufentanil has greater affinity for opioid receptors and a shorter EHL than fentanyl, why?
Twice as lipophilic as fentanyl
Sufentanil induction & infusion doses:
IVP: 0.1-0.2mcg/kg
Infusion: 0.1-0.2mcg/kg/hr
Alfentanil potency v fentanyl; alfentanil v. morphine:
Alfentanil is 1/3 potency of fentanyl, alfentanil is 20x more potent than morphine
Compare lipid solubility of alfentanil and fentanyl:
Alfentanil is less lipid soluble than fentanyl
Why did alfentanil lose popularity?
Unpredictable responses to medication administration, and the development of remifentanil.
What drug has been shown to prolong the metabolism of alfentanil (Alfenta) leading to prolonged respiratory depression and sedation?
Erythromycin
Drug 100x more potent than morphine, and equipotent to fentanyl:
Remifentanil
Metabolism of Remifentanil:
Non-specific plasma and tissue esterases
How does the Vd of remifentanil compare to the other opioids?
smallest Vd
Remifentanil CSHT:
<5 minutes
Remifentanil has the potential to cause glycine neurotoxicity, how does this impact administration?
No epidural/intrathecal administration
What plan should be in place for patients on remifentanil in the OR once they head to the PACU.
The administration of a longer-acting opioid.
This drug is an NMDA antagonist used in heroin addiction, it is a racemic mixture with a long half-life and has the potential to prolong QT intervals:
Methadone (methadose, dolophine)
Opioid usually combined with Tylenol:
Hydrocodone
This oral opioid is 10x more potent than morphine, has rapid onset, but poses high risk of N/V:
Oxymorphone (Opana)
This prodrug is metabolized into morphine. It is used as a cough suppressant, and has minimal sedation, but can lead to N/V, constipation, and dizziness:
Codeine
Patients lacking CYP2D6 or taking Quinidine will have difficulty metabolizing this drug into it’s active form:
Codeine
Rapid metabolizers of codeine experience:
Toxicity
Pure opioid competitive antagonist:
Naloxone (narcan)
Naloxone dose:
0.4-0.8mg IV
onset 1-2m
duration 1-4h
Naloxone SE:
Pain
Pulmonary edema
sudden death
This peripheral opioid mu antagonist maintains analgesia while also treating delayed gastric emptying and N//V.
Methylnaltrexone (Relistor)
Mu selective oral peripheral antagonist that depends on gut flora for metabolism, is approved for ileus and constipation treatment, but could lead to unwanted CV effects:
Alvimopan (Entereg)
Peripherally acting mu-opioid antagonist with high abuse potential, used for constipation:
Naloxegol (Movantik)
This oral opioid antagonist with high oral efficacy, used in the treatment of opioid dependence and ETOH withdrawal; however, active metabolite can lead to prolonged elimination:
Naltrexone (Vivitrol)
All opioid agonist-antagonists have a ceiling on their clinical effects, what does this mean?
Increased doses will not increase respiratory depression or analgesic effects further.
What effects seen with opioid agonist-antagonist differ from pure agonists?
Dysphoria, competitive antagonism at mu receptors, and agonize kappa receptors.
This agonist-antagonist reverses narcotic-induced postop ventilatory depression, maintains analgesia, and relieves itching.
Nalbuphine-Nubain
NSAIDs act as:
analgesic, antipyretic, and anti-inflammatory