Analgesics

• 5th VS

• a SUBJECTIVE experience

  • always listen to pt and trust their interpretation

when a larger dose is required to produce the same response that could formerly be elicited by a smaller dose

withdrawal syndrome will occur if drug is stopped/reduced

compulsive substance use despite harmful consequences, both tolerance and dependence occur

• direct stimulation of pain receptors

  • somatic: skin, bone, joint, muscle, connective tissue

    • dull, aching, throbbing pain

    • well-localized pain

  • visceral: internal organs (large intestine, pancreas)

    • deep, aching, squeezing pain

    • referred/well-localized pain

caused by peripheral nerve injury rather than stimulation of pain receptor

• causes: diabetic peripheral neuropathy, HIV, antiretroviral therapy

• burning, tingling, “pins and needles”

• does not respond well to traditional analgesics

• meds:

  • TCAs

  • anticonvulsants

  • SSNRI

  • gaba analog

• simple

  • heat/cold

  • exercise

  • massage/relaxation

• minimally invasive

  • TENS (electrical nerve stimulation)

  • acupuncture

  • ultrasound

• invasive

  • surgery

  • radiation

  • nerve block

• psychotherapy (better for chronic pain)

  • counseling

  • support groups

  • meditation

  • hypnosis

  • pt education

• for acute to moderate pain

• ceiling effect

• DO NOT produce tolerance/physiological dependence

• majority OTC

  • aspirin

  • acetaminophen

  • NSAIDs

• inhibits COX 1 & 2 centrally and peripherally

  • decreases prostaglandins & inhibits platelet aggregation

• dose depends on indication

  • low → antiplatelet (75-81 mg)

  • medium → antipyretic/analgesic (650-4000 mg)

  • high → anti-inflammatory (4000-8000 mg)

• primarily used for mild/moderate pain; antiplatelet agent

• GI issues (dyspepsia, ulcers)

• anticoagulant, bleeding

• impaired kidney function

• salicylism → tinnitus, HA, dizziness

• reye’s syndrome → avoid in children

• analgesic - decrease pain

• anti-inflammatory - decrease inflammation

• antipyretic - decrease fever

• anti-platelet - decrease clotting

• non-salicylated

• inhibits COX 1 & 2, decreases prostaglandin synthesis

• use: analgesic, antipyretic, anti-inflammatory

• mild to moderate pain

• first line analgesic

• renal dysfunction

• GI inhibition of gastric mucosa

• BLACK BOX:

  • MI

  • stroke

  • GI bleeding/ulcers

• cox-2 inhibitors

• selectively inhibits cox 2

• preserves protective effects of prostaglandins on GI mucosa

• increase risk of adverse cardiac effects (pulled off market)

• anticoagulants

  • increased bleeding risk

• steroids/glucocorticoids

  • increased gastric bleeding/ulceration risk

• alcohol

  • increased bleeding risk

• ibuprofen + low dose aspirin

  • decreases antiplatelet effect

• inhibits COX in brain but not a peripheral sites

• use: analgesic, antipyretic, NO anti-inflammatory/antiplatelet effects

• max daily dose

  • acute: 4 g

  • chronic: 3 g

• caution in hepatic impairment/heavy alcohol users

  • limit ≤2 mg/day

• minimal!

• BLACK BOX:

  • overdose on APAP if also using narcotic combo product

  • voted to reduce max daily dose to <4 g/day

• when used for superficial + localized pain → can achieve high local concentration w/ low systemic exposure

• for acute sprain and strains

  • reduced pain by at least 1/2 in 20-50% people when used for 7 days

• for hand and knee osteoarthritis

  • reduced pain by at least 1/2 in 10-20% people when used for 6-12 weeks

• ADRs: skin irritation

• MOA: causes skin irritation → vasodilation; results in reddening of skin + soothing feeling of warmth

• no studies showing benefit for acute/chronic pain

• ADRs: skin irritation → pain, swelling, blistering

  • not common

• MOA: binds to receptors in skin responsible for sending signals that cause pain perception

• produced mild tingling/burning sensation

• do not use on broken/irritated skin

• no good evidence to support use

  • high-concentration form approved in US for peripheral postherpetic neuralgia (Rx)

    • must continue 3-4 days if relief achieved

• 40% experience itching/rash

• cough, runny nose if particles inhaled

  • use gloves/thoroughly wash hands

• MOA: numbs superficial nerves/blocks pain signals; blocks impulse propagation → dampens pain signal tranmission

• does NOT decrease inflammation

• for post-herpetic neuralgia

• ADRs: skin rash, itching, hives

• MOA: binds to opiate receptors in brain to alter perception of pain

• for moderate to severe pain

• multiple receptor types (mu, kappa, delta, nociceptin)

• no ceiling effect, easily titrated

• ADRs:

  • CONSTIPATION (most common)

  • RESPIRATORY DEPRESSION

  • drowsiness/sedation

  • itching/pruritus

  • N/V

• prototype opioid analgesic

• natural substance from opioid plant

• first line agent for moderate/severe pain

• PO, IV, IM, SQ, PR (rectal), IT (intrathecal)

• immediate/sustained release forms

morphine-like opioid

• brand - Dilaudid

• moderate/severe pain

• more potent than morphine

• IV, IM, SQ

morphine-like opioid

• brand - Oxycontin

• moderate/severe pain

• immediate/sustained release

• only PO

• 2/3 potency of morphine

• available as combination w/ ASA, APAP, ibuprofen

morphine-like opioid

• brand - Demerol

• 1/10 potency of morphine

• shorter duration of action than morphine

• IV, IM, SQ, PO

• active metabolite (normeperidine) can cause tremor, muscle twitching, seizures

  • caution in elderly, pts w/ renal impairment

morphine-like opioid

• 80x potency of morphine

• shorter acting than morphine

• often used in anesthesiology as adjunct to general anesthesia for surgery

• no PO forms

• similar potency of morphine

• PO, IV, IM, SQ

• delayed onset, longer duration of action

• used for chronic pain, narcotic treatment programs (ex. heroin addiction)

• stimulates receptor, but not to full degree

advantages

• less addictive potential

• less respiratory depression

disadvantages

• ceiling effect

• ADRs: may precipitate withdrawal in opioid tolerant pts

• MOA: affinity for all opioid receptors; completely reverses effects of opioid overdose

• rapidly reverses respiratory depression

• treats opioid induced pruritus

• intranasal most common form

• IV, IM, SQ available

• short duration of action

• ADRs: severe withdrawal reaction

• MOA: bind to Mu opioid receptors

• less respiratory depression than natural opioids

• very addicting

• ADRs: severe withdrawal reactions

• for muscle spasms (involuntary muscle contractions, can cause intense pain)

• causes:

  • inadequate blood supply

  • dehydration

  • pregnancy

  • muscle injury/overuse

  • neurogenerative disease

• CNS depressants

  • increased respiratory depression/sedation

• anticholinergic drugs

  • increased constipation/urinary retention

• hypotensive agents

  • increased hypotension

1. laxatives

   1. senna + docusate

   2. bisacodyl

2. antihistamines

   1. diphenhydramine

   2. hydroxyzine

3. antiemetics

   1. prochlorperazine

   2. promethazine

• pain from nerve injury

• causes

  • diabetic peripheral neuropathy

  • HIV and antiretroviral therapy

• description of pain

  • burning, tingling, “pins and needles”

• does not respond well to traditional analgesics

  • may require non-analgesic therapy

• tricyclic antidepressants

• anticonvulsants

• SSNRIs

• pregabalin

• inappropriate dx or unknown etiology

• misunderstanding of pharmacology/pharmacokinetics

• adverse effects

• fear of addiction

• unrealistic goals for therapy

• patient barriers

• involuntary contractions of a muscle/group of muscles

• muscles become tightened/fixed

  • intense pain

• causes:

  • inadequate blood supply

  • dehydration

  • pregnancy

  • muscle injury/overuse

  • neurodegenerative disease

    • MS

    • MG

    • stroke/spinal cord injury

• interferes w/ the release of calcium ions in skeletal muscle (contraction)

• uses:

  • muscle spasms

  • malignant hyperthermia

• ADRs

  • liver toxicity/failure

  • CNS → confusion, speech/visual disturbances, seizures, severe sedation

  • pleural effusion

• may involve GABA inhibition

• appears to affect monosynaptic reflexes

• uses:

  • muscle spasms

  • alcoholism

• ADRs:

  • CNS → dizziness, sedation, weakness, fatigue

  • anticholinergic

  • SEVERE WITHDRAWAL SYMPTOMS

• withdrawal syndrome

  • worse w/ long term use

  • symptoms

    • visual/auditory hallucinations

    • delusions

    • agitation

    • seizures

  • prevent by slow dose reduction before stopping

• works in CNS to decrease muscle spasm activity

• no direct effect on muscle function

• effects similar to TCAs

  • seizures

  • arrhythmias

  • anticholinergic effects

  • CNS depression

  • sedation

• central alpha 2 agonist

• uses:

  • back spasms (not pain)

  • multiple sclerosis

  • anticonvulsant

• ADRs

  • liver failure

  • hypotension

  • increased spasms

  • CNS depression

  • constipation

  • diarrhea

  • stomach pain