Opioids Flashcards
MOA of opioids
Have G protein coupled actions on neurons doing the ff:
- Close voltage gated Ca++ channels on presynaptic terminals and reduce transmitter release
- Open K+ channels and hyperpolarize and thus inhibit postsynaptic neurons
Opioid side effects with minimal or no tolerance
Miosis
Constipation
Convulsions
Side effects of opioids NOT mediated by opioid receptors
Nausea and vomiting (stimulaitaon of CTZ at 4th ventricle)
Hypotension - histamine release
Pruritus - histamine release
Triad of opioid overdose
Pupillary constriction
Comastose state
Respiratory depression
Antidote for opioids
Naloxone
Opioid with shortest and longests half-lives
Shortest: REMIFENTANIL
(3-4 mins)
Longest: BUPRENORPHINE
(4-8 hours)
Opioid receptor that has euphoria effect
Mu1
Opioid receptor that has constipation effect
Mu2 (marked)
Kappa
Opioid receptor that has dysphoria effect
Kappa
Agonists of mu receptors
Endorphines
Morphines
Synthetic opioids
Agonists of kappa
Dynorphins
Agonists of delta
Enkephalins
List the drugs: full agonists to opioid receptors
Morpine Meperidine Methadone Hydromorphone Oxymorphone Fentanyl (100x more potent than morphine) Levorphanol Heroine
List the drugs: weak-to-moderate agonists to opioid receptors
Tramadol (dual-acting) Loperamide Codeine (central antitussive)* Dextrometorphan* Oxycodone* Hydrocodone* Dihydrocodeine* *partial agonists
Mixed agonists-antagonists
Buprenorphine Butorphanol Nalbuphene Nalorphene Pentazocine Levallorphan
Antagonists to opioid receptors
Naloxone
Naltrexone (also used for alcohol dependence)
Nalmefene
Diprenophene
Doesn’t cause contraction of sphincter of oddi
Meperidine
Good for acute pancreatitis
NMDA receptor antagonist
Dextrometorphan
List the drugs:weak agonists
Propoxyphene (used for opioid withdrawal, restless leg syndrome)
Levopropoxyphene
Dextropropoxyphene
“Actually lowers seizure threshold”
Meperidine
“Long half-life, so dapat admitted”
Methadone
“Partial agonist , so may cause precipitation of withdrawal” (???)
Buprenorphine
“Kappa agonist, di tayo masaya, dysphoria”
Nalbuphene
May cause serotonin syndrome when used with SSRIs or MAOIs
Codeine
Dextrometorphan
Withdrawn because of fatal cardiotoxicity
Propoxyphene
Group 1c antiarrhythmic activity
Commonly used in suicides
Propoxyphene
Used for opioid withdrawal states
Bupronorphine
Used for post-op shivering
Butorphanol
May cause seizures and delirium
Meperidine
(1/10th as potent compred to morphine)
*decreases seizure threshold (also tramadol)
*c/i in patients with epilepsy
*if given with MAOi -> hyperpyrexic coma
*if given with SSRI -> serotonin syndrome (also tramadol
Most pronounced anti-shivering effect
Meperidine
a2 antagonism
Used for opioid dependende
Methodone
(Methadone maintenance therapy)
*currently being investigated as a novel treatment for leukemia
Will not cause miosis
Meperidine
D/t atropine-like effects
Notes on tramadol
5-10x less potent than morphine
S/E profile vs other opioids: low tendency for respiratory abuse and low chances for developing tolerance and dependence
