Principles of Pain Management

inflammatory chemical mediators

1. substance P

2. prostaglandins

3. bradykinins

4. histamine

anti-inflammatory

1. serotonins

2. endorphins

3. enkephalins

chronic primary pain

chronic pain with no evidence of structural or nerve

chronic secondary pain

chronic pain because of an underlying conditions

what can you give acute pain

• APAP

• NSAIDS

• opiods

what do you give for chronic pain

• opioids

• non cancer (neuropathic, osteoarthritis, gout, fibromyalgia) gabapentin, TCAs, SNRIs, SSRIs, COX-2 inhibitors

what are the goals of pain management

1. improve perception

2. improve daily impairment/function

steps for prescribing opioids

1. determining initiation

2. selecting opioids

3. duration and follow up

4. assess risk and harms

start opioids on the __________ possible dose

lowest

what is the maximum opioid amount that you should not exceed (provides no more benefit but increases addiction potential)?

50 mme/day

what should you NOT combine opioids with?

benzodiazepines

acetaminophen PLUS DOSE

• MOA not fully understood

  • inhibit serotonin inhibition

  • inhibition of heat regulation

• use: mild-moderate pain and fever

• dose: 325-650 mg q4-6H prn or 1 g q6H prn

  • acute MAX daily dose = 4 g/day

• SE: hepatotoxicity (from glutathiamine stores being depleted), skin erythema, skin blister, rash, hearing loss

• drug interaction with alcohol

• used for migraines in pregnancy and lactation

example of irreversible COX inhibitor

aspirin

example of REVERSIBLE non-selective cox inhibitor

ibuprofen

example of REVERSIBLE selective cox 2 inhibitor

celecoxib

what does cox 1/prostaglandin cause?

1. uterine contraction

2. less secretion of acid

3. increased production of protective mucus

what does cox 2/prostacyclin cause?

1. hypothalamus increases body temp

2. nociceptor sensitization

3. attract immune cells

4. vasodilation?

aspirin

• interferes with production of thromboxane A2, inhibits PLT aggregation, antipyretic, analgesic, anti-inflammatory

• kawasaki - start with high dose and reduce

• dose dependent effects - migraines, OA, RA, prevention of MI, TIA, DVT

• chronic use → gastric protection

• SE N/V/D, thrombocytopenia, bleeding, anemia

• AVOID in children >12yo for reyes EXCEPT for kawasaki

• CI in ulcer, hemorrhage, G6PD deficiency, renal, kidney, heart failure

• ASA exacerbated respiratory disease (AERD)

• CI in third trimester because of pre closure of ductus arteriosus

• overdose: tinnitus, N/V, metabolic acidosis, respiratory alkalosis

ibuprofen

• reversible inhibitor of cox 1 and 2 → decreased prostaglandin, antipyretic, anti-inflammatory, analgesic

• MAX 2400 PO qD

• take with food, gastric protection

• SE: edema, decreased Hgb, increased BP

• avoid alcohol! BBW = GI bleeding, CV thrombotic events

• interactions with ACE I, ARBs, CCBs, loops, BBs

• dose adjust for renal insufficiency

what three meds combined cause the “triple whammy” of acute kidney injury?

1. ibuprofen (vasoconstrict)

2. ACE inhibitors or ARBs (vasodilate)

3. loop diuretics (decreases volume)

opioid receptor mu

• analgesia

• resp depression

• sedation

• euphoria

• dependence

• decreased GI motility

kappa opioid receptor

• analgesia

• sedation

• decreased GI motility

opioid delta receptor

• no interaction

incomplete cross tolerance

reduce dose of new opioid by 30-50% when switching to adjust

what do you want to prescribe a patient when giving them opioids?

laxativewh

what do you give a opioid using pt when laxatives are not working?

peripherally action mu opioid receptor antagonist (PAMORA)

naldemedine, naloxegol, methylnaltrexone

selectively block mu opioid receptors only in the Gi tract without crossing the BBB

what are ALL opioids contraindicated with?

head trauma bc increased ICP risk

class I drugs

• no currently accepted medical use → illegal

• heroin, cannabis

class II drugs

high potential for abuse

morphine, fentanyl, hydromorphone, meperidine, hydrocodone, methadone, oxy, cocaine

class III drugs

moderate to low potential for abuse

buprenorphine, codeine

class IV drugs

low abuse potential

tramadol

class V drugs

very low abuse potential, combined with something else

cough syrups with low dose codeine, diphenoxylate

morphine

• binds to mu receptor

• 30-60 min onset

• take with food

• give bowel regimen prohpylactically

• constipation, sedation, confusion, myoclonus, resp depression

• dont give with benzos

• monitor RR

• tolerance over time

• standard for opioids!

hydromorphone (dilaudid)

• class II

• way more potent than morphine

• 30 mg morphine = 7.5 mg hydromorphone

• similar to morphine

meperidine

• class II

• similar to morphine but shorter duration (2-3 hrs)

• limit use bc accumulation of toxic metabolite normeperidine, avoid in CKD

• toxic metabolite = agitation, tremors, seizures, myoclonus

• avoid with MAOIs bc serotonin syndrome

• limited utility

oxycodone

• class II

• binds to mu receptor for analgesia

• acute or chronic pain

• IR, ER, abuse deterrent formula

• can be a combo with APAP (perc), ASP, or ibuprofen

• CI in RR depression and probs

• dont give with benzos

fentanyl

• class II

• acute and chronic pain, 30-60 min onset

• patch form!

• RR depression, constipation

• 50-100x more potent than morphine

• ONLY FOR OPIOID TOLERANT PTS

what are the 4 qualifications for receiving a fentanyl patch?

1. opioid tolerant

2. severe, continuous pain

3. stable pain

4. cannot take oral medication

can you administer any other medications with a fentanyl patch?

yes, you can give a breakthrough medication

tramadol

• class IV

• WEAK mu receptor agonist

• moderate to severe pain

• BBW for RR depression

• CI in all children <12yo, <18 yo after tonsillectomy or adenoidectomy, MAOI use within the last 14 days

• lowers seizure threshold

methadone

• class II

• mu receptor agonist, NMDA receptor agonist

• alternative for failed opioids, treatment of substance abuse

• LONG HALF LIFE ~34 hrs, effects in 4-8 hours → 3-5 days for full effect

• cardiac toxicity, QT prolongation !!

• DONT take with CYP3A4 inhibitors (z pack)

• ECG prior to starting

• highest risk of OD, dont titrate too quick

PCA pumps are used for…

• acute pain (pancreatitis, trauma)

• chronic

what is often used in PCA pumps?

• morphine, fentanyl, hydromorphone, meperidine

• intial loading dose, PCA dose, lockout interval, cont infusion rate, 1 and 4 hr limits

• cognitive screening

what are some complications of PCA pumps?

• malfunction

• PCA by proxy

• bad syringe placement

• machine tampering

do NOT exceed ____MMEs for meds

50

methadone conversion is _______________

do you convert to or from methadone?

what percentage dose reduction do you do?

non-linear

TO

75-90%

use only ________ of equivalent dose when switching to a different opioid

50-75%

examples of SNRIS

duloxetine

venlafaxine

examples of SSRIs

fluoxetine

citalopram

paroxetine

examples of TCAs

amitriptyline

examples of anticonvulsants

pregabalin, gabapentin

FIRST LINE FOR diabetic peripheral neuropathy

duloxetine, pregabalin

FIRST LINE FOR postherpetic neuralgia

gabapentin and pregabalin

FIRST LINE FOR trigeminal neuralgia

carbamazepine