Pain management Flashcards
TYPES OF PAIN
- Nociceptive
- Inflammatory
- Neuropathic
- Functional: pain sensitivity due to an abnormal processing or function of the central nervous system in response to normal stimuli.
TREATMENT OF PAIN
- For mild pain (1–3/10), management should be started at step 1; non-opioid
- For moderate pain (4–6/10), it should be started at step 2; mod opioid + non-opioid +/- adjuvant (codeine + acetaminophen)
- For severe pain (7–10/10), it should be started at step 3; **strong opioid + non-opioid +/- adjuvant **
NONOPIOID ANALGESICS
- Nonopioid analgesics have an analgesic ceiling effect.
- They reach maximal analgesia at low to moderate doses.
- includes acetaminophen and NSAIDs
Opioids for Mild- Moderate Pain
- Codeine
- Hydrocodone
- Oxycodone
- Meperidine
- Tramadol
Opioids for Moderate- Severe Pain
- Morphine
- Hydromorphone
- Oxymorphone
- Levorphanol
- Fentanyl
- Sufentanil
- Methadone
BREAKTHROUGH PAIN
- Transitory severe acute pain that occurs on a background of chronic pain that is adequately controlled by an opioid regimen.
- Rescue doses are given for relief.
- Typically, a short-acting supplemental opioid is used.
- Atypical rescue dose is 5 to 15% of the basal daily requirement of opioid.
- Breakthrough pain may be targeted with a transmucosal fentanyl formulation.
Opioids used in Patient-Controlled Analgesics (PCA) devices include
morphine, hydromorphone, fentanyl, and methadone.
MEPERIDINE
- half-life of 3 h.
- Its principal metabolite, normeperidine, has a half-life of 15-20 h.
- Normeperidine produces significant adverse effects when it accumulates:
- Dysphoria, Myoclonus, Seizures
- NOT RECOMMENDED FOR ROUTINE DOSING
MIXED AGONIST-ANTAGONISTS contraindications
- Mixedagonist-antagonists are not recommended as routine analgesics, as their dosing is limited by a ceiling effect.
- Additionally, pentazocine, nalbuphine and butorphanol cause psychotomimetic adverse effects.
- Mixed agonist-antagonists should not be used in a patient already taking a pure agonist opioid.
- Competition for the opioid receptors may cause a withdrawal reaction.
MANAGING OPIOID ADVERSE EFFECTS
Urticaria, pruritus: Can be managed with hydroxyzine or diphenhydramine.
Constipation: combination stimulant/softener can be useful. Bulk-forming agents require substantial fluid intake and are not recommended for patients with advanced disease and poor mobility.
Nausea/vomiting: hydroxyzine, metoclopramide or prochlorperazine.
Respiratory depression: naloxone to reverse resp. effects
ANALGESIC ADJUNCTIVE AGENTS (COANALGESICS)
- ANTIDEPRESSANTS
- ANTICONVULSANTS
- GLUCOCORTICOIDS
- OTHER DRUGS
ANTIDEPRESSANTS AND ANTICONVULSANTS
- Mainstay of treatment for several neuropathic pain syndromes.
- Serotonin and norepinephrine mediate descending inhibition of ascending pain pathways in the brain and spinal cord.
- SSRIs are less effective than SNRI
TCAs commonly used as analgesics are (w AE):
- Amitriptyline
- Imipramine
- Desipramine
- Nortriptyline
Adverse
- Associated with their anticholinergic activity.
- constipation, dry mouth, blurred vision, cognitive changes, tachycardia, urinary hesitation.
- orthostatic hypotension, falls, weight gain, sedation.
WARNINGS, PRECAUTIONS & CONTRAINDICATIONS
- TCAs should be administered cautiously in patients with:
- Angle-closure glaucoma
- BPH
- Urinary retention
- Constipation
- CV disease: class Ia effects
- Impaired liver function.
- TCAs should be avoided in patients with:
- Second- or third-degree heart block
- Arrhythmias
- Prolonged QT interval
- Severe liver disease
- Recent acute MI
VENLAFAXINE & DULOXETINE
- SNRIs selectively inhibit reuptake of serotonin and norepinephrine.
- SNRIs lack the antihistamine, α-adrenergic blocking, and anticholinergic effects of TCAs.
- effective for several types of neuropathic pain.
Adverse effects
- Nausea, sexual dysfunction, somnolence.
- SNRIs are better tolerated than TCAs.
Gabapentin & Pregabalin
Carbamazepine
- ANTICONVULSANTS
- Useful in the management of neuropathic pain.
- GABAPENTIN & PREGABALIN
- MOA: Block v-g **calcium-channels. **This leads to reduction of the influx of calcium into neurons decreasing release of glutamate, norepinephrine, and substance P.
- Adverse: Dizziness, somnolence, peripheral edema.
- DOC for trigeminal neuralgia.
- MOA: blocks v-g sodium channels in sensory neurons
- Adverse:
- Drowsiness, dizziness, nausea and vomiting.
- Carbamazepine-induced leukopenia is not uncommon, but it is usually benign.
- Aplastic anemia is a rare side effect.
