Pain Management Flashcards
What are the steps of processing pain?
- Transduction (stimulation of the nociceptors)
- Conduction
- Transmission (Pain traveling up spinal cord)
- Perception
- Modulation
What is the cause of sharp, well-localized pain?
- large diameter
- sparsely myelinated fibers
What fibers are involved with aching, poorly localized pain?
- small-diameter
- unmyelinated
Somatic Pain
- from skin, bone, joint, muscle, connective tissue
- throbbing, well localized
Type of pain from large-diameter sparsely myelinated Alpha and Delta
sharp, well-localized pain
Type of pain from unmyelinated, small-diameter C fibers
dull, aching, poorly localized
Where is the blockade of N-methyl-D-aspartate (NMDA) receptors found
dorsal horn
Central sensitization
- increase in excitability or responsiveness of neuron within the CNS
- Associated with inflammatory pain after injury
Neuropathic pain
nerve damage
ex. post-herpetic neuralgia, diabetic neuropathy
Functional pain
abnormal operation of nervous system
ex. Fibromyalgia, IBS, tension-type headache
Non-pharmacologic therapy for pain
- physical manipulation
- heat or cold
- massage
- exercise
- TENS (transcutaneous electrical nerve stimulation)
- cognitive and behavioral
Pain - PPQRST
Palliative Provocative factors Quality Radiation Severity Temporal
Treatment goal difference between acute and chronic pain?
acute - pain reduction
chronic - functionality
Salicylates
- Acetysalicylic acid (ASA)
- irreversibly binds to platelets for 7-10 days - Choline and magnesium trisalicylate
- no acetyl group, doesn’t alter platelets - Diflunisal
- no acetyl group, doesn’t alter platelets
Non-opioid analgesics
- Salicylates
- Acetaminophen
- anthranilic acid (ex. Mefenamic acid)
- Indolacetic Acid ( ex. Etodolac)
- Phenylacetic acids (ex. Diclofenac)
- Propionic Acids (ex. Ibuprofen, Naproxen)
- Pyrrolacetic acids (ex. Ketorolac (toradol))
- Cox-2 selective (ex. Celecoxib)
Acetaminophen max dosing
Elderly: max of 2gm/day
-Normal adults: max of 3gm/day
Phenylacetic Acids
Diclofenac potassium
Diclofenac epolamine, (patch)
Diclofenac sodium (topical gel, for osteoarthritis)
Propionic acids
- Ibuprofen (max daily dose for inflammation: 3200mg, max dose of fever/dysmenorrhea: 1200mg)
- Naproxen - osteoarthritis; Naproxen sodium for acute pain
Pyrrolacetic Acids
- Ketorolac (Toradol) Parenteral max of 5 days
- Oral ketorolac - max of 5 days
- Nasalspray ketorolac: one spray, in one nostril. Max of 5 days
Celecoxib and ASA
If using low dose ASA in a patient, give it before the Celecoxib
NSAIDS: adverse reactions and monitoring
- Upper GI bleed
- monitor with CBC, stool guaiac - Acute Renal Failure
- monitor serum creatinine (esp. if CHF, hypovolemia)
Acetaminophen: adverse reactions and monitoring
- Hepatotoxicity
- ALT/AST
- Liver synthesis tests
- PT/INR, albumin
- Acetaminophen concentration
Opioids: Phenanthrenes - Potency
Greatest to least potency:
Oxymorphone
Hydromorphone (Dilaudid) (1.5 x weaker than oxymorphone)
Morphine (10x weaker than oxymorphone)
-morphine PO has the greatest first pass effect (ex. have to give 3x the dose orally)
-Codeine 15-30x weaker than Oxymorphone
-Hydrocodone 30x weaker
-Oxycodone 30x weaker
Opioids: Phenanthrenes - Relative histamine release
Morphine (naturally occuring) +++
Hydromorphone (semi-synthetic) +
Oxymorphone (semi-synthetic) +
Codeine +++
Levophanol (semi synthetic) +
Hydrocodone (Vicodin) N/A
Oxycodone (OxyContin) (semi-synthetic) +
Morphine
drug of choice in severe pain
For cancer patients: can use immediate-release product with controlled release product to control breakthrough pain
-can cause sphincters to close more tightly, sometimes causing more pain
Hydromorphone (Dilaudid)
more potent than morphine, otherwise no advantages
Oxymorphone (Opana)
Most potent Phenanthrene
- can use immediate + controlled release for cancer pt.
- ER reformulated to deter misuse
Codeine (methylmorphine) General
- Mild to moderate pain and cough suppression
- Needs CYP450, 2D6 to metabolize to morphine (prodrug metabolize to morphine)**
DON’T use in children or with breastfeeding
Phenylpiperidines: General
- Meperidine (Demerol)
Histamine: +++
Strength: 100x weaker
-DON’T use, toxic metabolite accumulation can cause seizures
- Fentanyl (sublimaze, Duragesic Actiq)
Histamine: +
Strength: 0.1x weaker**
Phenylpiperdines: Meperidine (Demerol)
DON’T USE:
- oral form
- in renal failure
May precipitate tremors, myoclonus, seizures*
**Dilates eye (mydriasis) not constriction (miosis)
*can cause serotonin syndrome with MOAIs
Phenylpiperdines: Fentanyl
- Don’t use the transdermal patch for acute pain (dose too low)
- Transmucosal, intranasal, sublingual
Diphenylheptanes: General
Methadone
histamine: +
Dose: variable!!**
ADE: QT prolongation*****
avoid titrations more frequently than every 2 weeks
Agonist-Antagonist (these contain Naloxone)
- Pentazocine (historical, not used today)
- 3rd line agent
These are 2nd line:
- Buprenorphine
dose: 0.3x weaker than oxymorphone
- may not be effecting in reversing respiratory depression - Nalbuphine
- Butorphanol
**May precipitate withrdrawal in opiate-dependent patients
Opioid Analgesics: Central analgesics
- Tramadol
dose: 120x weaker than oxymorphone
- can be helpful for neuropathic pain
- Pro-drug, must be converted to produce analgesia
-Risk of seizure, serotonin syndrome, hypoglycemia
*Decrease dose in elderly (75+) and renal impairment
Analgesic Drug monitoring
- Respiratory depression
- respiratory rate, end-tidal capnography*
- The newer a patient is to opioids more likely they are to have this
- Sleep apnea, COPD at higher risk - Constipation
- use Bristol scale to assess
Opioids: ADEs
Sedation, Nausea, vomiting: will decrease over time
Hypogonadism: fatigue, depression, sexual dysfunction, amenorrhea
Sphincter: monitor for biliary spasm, urinary retention
Opioid antagonist: Naloxone
- synthetic
- IV
- duration is shorter than opioid so need to repeat dose*
Neuropathic pain
-Chronic type of pain Treatments: 1. Anticonvulsants 2. TCA 3. SNRI 4. Opioid 5. Topical analgesics
Chronic Pain: Anticonvulsants: Gabapentin [neurontin]
-decreases neuronal excitatory neurotransmitters by affecting voltage-gated calcium channels
ADE: Dizziness, fatigue, peripheral edema, tremor, headache, amnesia, ataxia, weight gain
Chronic Pain: Anticonvulsants: Pregabalin [lyrica]
-structurally related to GABA, but doesn’t bind to GABA receptors
- Antinociceptive and anticonvulsant activity
- *peripheral neuropathy**
ADE: peripheral edema**, weight gain, tremor, dizziness
Chronic pain-Adjunctive therapy: TCA, SNRI, Duloxetine
block reuptake of serotonin and norepinephrine enhancing pain inhibition
Mild pain treatment
Acetaminophen +/- NSAID
Moderate pain treatment
Opioid + acetaminophen or NSAID
Severe Pain treatment
Opioid
which 2 opioid analgesic drugs are prodrugs
- Codeine
2. Tramadol
What is the caution with using agonist/antagonist agents?
can produce opioid withdrawal in patients chronically taking opioid
Why should you avoid Meperidine?
short duration so frequent dosing
-toxic metabolite normeperidine (seizures)
What is the drug of choice for focal neuropathic pain?
Lidocaine
Intrathecal
injected into the spinal column subarachnoid space
-indicated for cancer-related pain
Ex. Morphine or Fentanyl
Epidural route
Ex. Morphine
Hydromorphone
Fentanyl
Sufentanil
-can do continual infusion with this route*
Ziconotide
MOA: unique mechanism, no action on the mu receptor
First line therapy for localized and nociceptive pain
What is the treatment algorhythm for low back pain
- heat, massage, acupuncture, CBT
- NSAIDs and skeletal muscle relaxants (acute <4 weeks)
- Chronic low back pain (>12 wks) NSAIDs are 1st line. Duloxetine, Tramadol are 2nd line
Neuropathic pain: treatment
1st line: TCA, SNRI, AED, lidocaine patch
2nd line: central analgesics, opioids
3rd line: capsaicins
–NSAID and acetaminophen - rarely effective
Heroine
- Diacetylmorphine (give the euphoric feeling, helps cross the BBB)
- metabolized to morphine
Opioids: What is thought to represent true allergy only
Bronchospasm
and sometimes angioedema
- severe angioedema
- severe hypotension
Pseudoallergy
- mast cell degranulation
- itching, flushing, sweating, mild hypotension
**depends on the concentration of the opioid at the mast cell
Which opioids are most commonly associated with pseudoallergy?
- codeine
- morphine
- meperidine
more potent opioid, less likely to release histamine
