Opioids
Mu receptors
: activation includes analgesia, respiratory depression, euphoria and sedation
Kappa receptors
: produces analgesia, sedation, and respiratory depression
Pure Opioid Agonists
: activate Mu and Kappa receptors, product analgesia, euphoria, sedation,
respiratory depression, physical dependence, constipation
Two subgroups
Strong opioid agonists: morphine
Moderate to strong opioid agonist: codeine oxycodone, hydrocodone,
Agonist-Antagonist Opioids
: when administered alone they produce analgesia, in combination with pure
opioid agonist they can antagonize analgesia caused by the pure agonist
Ex: Pentazocine (Talwin), butorphanol, buprenorphine
Pure Opioid Antagonist:
acts as an antagonist to Mu and Kappa receptors, used for reversal of CNS
depression
Ex: Naloxone (Narcan)
Opioid Agonists
Morphine
: pure opioid agonists, used for moderate to severe pain
Adverse Effects
Respiratory depression
Constipation
Orthostatic Hypotension
Urinary retention
Emesis
Euphoria and dysphoria
Sedation
Neurotoxicity
Precautions
Give sparingly with pts with impaired pulmonary function (asthma, emphysema, kyphoscoliosis,
chronic cor pulmonale, extreme obesity)
With other respiratory depressant drugs
Pt with inflammatory bowel disease can cause toxic megacolon or paralytic ileus
Could be intensified in pts with liver impairment
Pt with BPH could have urinary retention
Infants and older adults are more prone to respiratory depression
Pt with hypotension and reduced blood volume
Toxicity: coma, respiratory depression, pinpoint pupils
Fentanyl:
(Duragesic)
strong opioid agonist, 100x more potent than morphine
Routes:
parental
transdermal: change patch q72h, do not exposure to heat, not to be used for post-op pain
transmucosal: approved only for breakthrough pain in pts with CA at least 18 yeas old who
already take opioids around the clock and have tolerance
intranasal
Adverse effects: same as morphine, but greatest concern is respiratory depression
-levels can be increased by CYP34A inhibitors (ritonavir & ketoconazole)
Hydromorphone
: (diladid) strong opioid agonist
-less N/V than morphine
Routes
IR, ER, Oral Suppositories
Oxymorphone
: (Opana) strong opioid agonist, can cause less N/V than morphine
Routes
IR, 2mg q4-6h
ER
Oral
Suppositories
Codeine
: moderate to strong opioid agonist, also used as a cough suppressant, acts on Mu receptors
-schedule II alone but schedule III when combined with other drugs
-only available in tablets
Hydrocodone:
Equivalent to codeine, indicated for moderate to severe pain and cough suppression
-Schedule 2 drug, can be reversed with naloxone.
- IR 5mg tablet, can be combined with Acetaminophen or Ibuprofen (Norco, Vicodin, Lortab).
ER every
12-24hours.
