| What are analgesics? | Nociceptive Pain (headache, arthritic pain - non opioids)
Neuropathic Pain (Use Opioids, Anticonvulsants, TCAs, SNRIs)
Severe/Chronic Pain (Opioids) |
| What are pain transmission pathways? | Transduction (From peripheral nociceptors)
Transmission (Myelinated & Unmyelinated fibers to dorsal root)
Transmission (along spinothalamic tract ascending path)
Perception (In thalamus and hypothalamus)
Modulation (descending path) |
| How is classification of opioids? | Natural (Morphine and Codeine)
Semi-Synthetic (Hydromorphine, Hydrocodeine, Oxycodone, Oxymorphone, Diacetylmorphine (heroin))
Synthetic (Fentanyl, Meperidine, Methadone, Bramadol, Propoxyphene)
Endogenous Peptides (Endorphins, Enkephalins, Dynorphins) |
| How is morphine mechanism of action? | Strong mew R agonist, acts on opioids Rs in CNS and k Rs in spinal cord (decrease release of substance P) |
| What are the actions done by morphine? | Analgesia (no loss of conscious, relieve pain by raising pain threshold and altering perception, sense of euphoria)
Histamine Release (cause urticaria, sweat, vasodilation, bronchoconstriction)
Respiration (resp depression most common cause of death, tolerance quickly w/repeated exposure, depresses cough reflex)
Miosis (enhanced parasymp eye stimulation)
GI (Emesis, opioid induced constipation [inc tone and dec motility], increased biliary tract pressure [gallbladder contract])
CV (large dose: hypotension, bradycardia, CI in brain injury)
Hormone (increase PRL, GH, ADH)
Labor (prolongs stage 2 of labor) |
| What are therapeutic uses of morphine? | Analgesia, acute PE (relieves dyspnea due to vasodilation effect, reduces pre and after load), severe diarrhea, relief cough (although codeine and dextromethopran are better) |
| How are pharmacokinetics of morphine? | A (SC, IM, Oral, IV)
1st pass bioavailability 25%, affects fetus, least lipophilic opioid, metabolism (junction of glucuronic acid either very potent opioid or inactive), duration 4-6 hours
E: glomerular filtration |
| How are drug interactions and CI of morphine? | Interactions (Blocks serotonin reuptake -Serotonin hyperstimulation causing serotonin syndrome pt taking them w/SSRIs/Meperidine)
CI (Delivery women, asthma, cranial injury/ increased pressure) |
| What are opioid agonists? | Codeine, Tramadol, Heroin, Meperidine, Loperamide, Fetanyl, Methadone, Propoxyphene |
| What is codeine? | Moderate agonist, effective oral analgesic, less potent than morphine
low affinity for opioid Rs, converts to morphine to exert analgesic effect.
low potential for abuse, less euphoria than morphine |
| What is tramadol? | Synthetic codeine analog, weak mew R agonist, analgesic blocks NE and serotonin reuptake, tx mild to moderate pain. |
| What is heroin? | It gets converted to morphine with an intermediate monoacetylmorphine.
More fat soluble than morphine, enters brain easily.
Not for medical use. |
| What is meperidibe? | mew Rs agonist, control smooth muscles, dilates pupils (atropine like)
primary analgesic (not cough or diarrhea)
less urinary retention than morphine, less effect on uterine smooth muscle contraction employed in OBGYN. |
| What is loperamide? | Slows GI motility (antidiarrhea) reduces GI secretions |
| What is fentanyl? | Synthetic opioid, more potent than morphine 100%, anesthetic, highly lipophilic w/rapid onset and short duration of action (15-40 min)
Admin (IV, epidural during labor, intrathecal, sublingual, transdermal
Sufentanil more potent than fentanyl, Remifentanyl and Alfentanyl less potent |
| What is methadone? | Relief of chronic pain, tx of opioid abstinence syndrome and heroin dependence.
less euphoria, long duration of action, oral admin increase biliary pressure and constipation and physical dependence made. |
| What are opioid mixed agonists? | Pentazocine (agonist k Rs, weak antagonist at mew, analegesia and sedation, less euphoria than morphine, causes dysphoria and psychotomimetic effects, doesn't antagonize resp distress of morphine)
Nalbuphine (potent mew antagonist and k agonist, analgesic less dysphoric than pentazocine)
Buprenorphine |
| What is buprenorphine? | Semi-synthetic opioid, more potent than morphine
partial mew agonist
Admin: sublingual/PRL
long duration of action
Tx (opioid dependence (tablets), relief moderate to severe pain (PRL))
Shorter duration of withdrawal compared with methadone |
| What are opioid antagonists? | Naloxone (reverses coma and resp depression of opioids, effects of heroin overdose. IV injection after 30 s reverse the effects
half life 1-3 hours, competitive antagonist at mew (10 times higher affinity), k and lambda)
Naltrexone (longer duration of action than naloxone, hepatotoxic)
These have high affinity for opioid Rs but don't activate response, normal individuals no effect, if pt takes opioids reverses effect rapidly w/ sx of opiate withdrawal |
