Pain Management Flashcards
Compare and contrast the components of nociceptive pain vs neuropathic pain emphasizing those aspects that are most relevant to targeting pharmacotherapy
Nociceptive Pain: Receptors on A-delta or C fiber.
Pharm Targets: prostaglandin synthesis (decreases synthesis of a pain stimulator), stimulation of descending pain inhibitory pathway (opioids or increasing 5-HT in synapse
Neuropathic Pain:
Pharm targets: stimulation of descending pain inhibitory pathway, block of sodium channels, block of calcium channels, NMDA receptor block
Describe the mechanistic approach to multimodal management of acute pain.
Treatment is based on the severity of pain:
•Treat mild pain with non-opioids such as NSAIDs or acetaminophen with/without adjuvant analgesics
•Treat moderate pain with immediate-release, short-acting opioids with slow titration, with non-opioids (above) and with/without adjuvant analgesics
•Treat severe pain with immediate-realease, short-acting opioids with rapid titration, with non-opioids (above) and with/without adjuvant analgesics
What is the role of pain management: Opioid analgesics
u receptor agonist. Acts on supraspinal and spinal nerves.
Acute stimuli = Tissue injury > nerve injury > 0
What is the role of pain management: Local anesthetics
Block of voltage-sensitive sodium channels (VSSC) → reducing nociceptive stimuli action potential
- Provides intense, prolonged analgesia → decreases total amount of systemic opioids necessary (opioid sparing) and potential for opioid-related side effects
- Allows for earlier ambulation with decreased potential for DVTs (deep vein thrombosis); mobilizes secretions – better cough; earlier return of bowel function.
- Routes: Neuraxial (epidural or spinal) infusion or peripheral nerve block
- Side effects: Neurotoxicity, hypotension, dizziness, drowsiness
Can be used in severe pain treatment
What is the role of pain management: NSAIDs - Acetaminophen - COX-2 inhibitors
NSAIDS (acetaminophen) is a Non-specific COX inhibitor. Cox-2 inhibitors are Cox-2 selective inhibitors (duh).
All have site of action on Peripheral and spinal.
Tissue injury»_space; acute stimuli = nerve injury = 0
What is the role of pain management: α-2 adrenergic agonists (ie clonidine)
Primary action at postsynaptic α-2 adrenergic receptors on dorsal horn neurons and cells in locus ceruleus to modulate pain transmission.
- May decrease opioid requirements; generally reserved for severe intractable pain as adjunct to neuraxial opioids.
- Route: Epidural infusion
- Side effects: Analgesic efficacy limited by potential for hypotension, bradycardia, excessive sedation, and rebound hypertension upon withdrawal
What is the role of pain management: NMDA receptor antagonist (ie ketamine)
Block glutamate binding at NMDA receptors in the ascending pain modulatory pathway.
- Ketamine administration can reduce the development of tolerance to long-term opioid use.
- Routes: Administered as intravenous infusion and intranasal spray
- Side effects: Suboptimal tolerability profile limits usefulness; side effects include hypertension, diplopia, dizziness, arrhythmias, nausea-vomiting, psychotomimetic reactions.
Describe the mechanistic approach to the treatment of chronic pain
Unlike the treatment of acute pain, specific therapeutic classes are not used based on the severity of pain. Rather, multiple therapeutic classes are used, efficacy is noted and the regime is adjusted accordingly.
• Enhancement of descending pathway with opioids or antidepressants
• Decrease central sensitization with block of calcium channels (anticonvulsants) or NMDA receptors (ketamine)
• Decrease peripheral sensitization with block of sodium channels (anticonvulsants or local anesthetics)
Adjuvant meds are also added as needed. See page 10 for a list of adjuvant meds.
Role in chronic pain management: Tricyclic antidepressants (TCADs)
Inhibits reuptake of NE/5HT
Located in Supraspinal and Spinal nerves.
Nerve injury > tissue injury»_space; acute stimuli = 0
Role in chronic pain management: SSRIs
Enhances of descending inhibitory pathway
Block NE-5HT reuptake
Role in chronic pain management: Serotonin-norepinephrine reuptake inhibitors (SNRIs)
Enhances of descending inhibitory pathway
Block NE-5HT reuptake
Used as adjuvant medications to treat concurrent symptoms that exacerbate pain and/or provide independent analgesic activity for a specific type of pain
Used in Fibromyalgia
Role in chronic pain management: Anticonvulsants
Decrease in central sensitization by Blocking VSCC»_space; inhibit excess NT release
Decrease in peripheral sensitization by Blocking VSSC»_space; decrease in excess neurotransmission
Used in spinal cord injury, trigeminal neuralgia, diabetic neuropathy
Role in chronic pain management: Local anesthetics
Provides intense, prolonged analgesia → decreases total amount of systemic opioids necessary (opioid sparing) and potential for opioid-related side effects
Allows for earlier ambulation with decreased potential for DVTs (deep vein thrombosis); mobilizes secretions – better cough; earlier return of bowel function.
Role in chronic pain management: Nonopioid analgesics
Nonopiod analgesics are emphasized in chronic pain management
Include: traditional NSAIDs, acetaminophen, COX-2 selective. Best for mild-mod pain, particularly of somatic origin. Topical NSAIDs for pain localized to specific joints
Role in chronic pain management: Opioid analgesics
May be used for patients with acute neuropathic pain, neuropathic cancer pain, or episodic exacerbations of severe pain. Should generally be reserved for moderate to severe pain that adversely impacts function or quality of life. Long-acting opioids may be required in some patients (e.g., cancer pain). Short-acting opioids given on an as needed basis may be required for breakthrough pain during dose titration for long-acting opioids
