pain management Flashcards
pain
-unpleasant sensory and emotional experience that normally serves to alert an individual to actual or potential tissue damage”
-Causes of tissue damage which results in pain
-Exposure to noxious chemical, mechanical or thermal stimuli -> Acids, Pressure, Extreme heat
-Pathological process -> Tumor, Muscle spasm, Inflammation, Nerve damage
classification of pain
-acute- obvious cause, reversible, high HR and HTN
-chronic- not always obvious, not reversible, depression, withdrawal
-relation to cancer
-Pathophysiology (Nociceptive, neuropathic, visceral):
-Nociceptive – pain due to stimulation of nerve fiber by noxious stimulus (chemical, thermal, mechanical and/or ischemic)
-somatic: well localized to specific dermal, subQ or musculoskeletal tissue. Described as dull/aching pain. Can treat with opioids and non opioids
-Visceral : originates in thoracic or abdominal structures, poorly localized and distant from source of pain. Described as deep, aching and cramping. Treat with opioids/non opioids
-Neuropathic pain – usually caused by nerve damage to CNS or PNS. (nerve compression, diabetic neuropathy, post herpetic neuralgia) Often described as burning or stabbing and may radiate down arms and legs. Treatment w/ all forms of analgesics – variable and unpredictable.
-Idiopathic pain – often due to psychological factors with no known cause or origin
general anesthetics
-inhalational or parenterally to cause the loss of consciousness and prevent awareness of pain during surgery
local anesthetics
applied topically or locally to the site where the pain will originate to prevent transmission of pain impulse to spinal cord
analgesics
-Opioid analgesics – work primarily in CNS to inhibit the neurotransmission of pain
-non-opioid analgesics: Work primarily in peripheral tissues to inhibit formation of pain impulses from nociceptive stimuli. Inhibitors of prostaglandin synthesis. Also exert antipyretic and anti-inflammatory properties
-Aspirin
-NSAIDS
-Acetaminophen:
-no anti-inflammatory properties
-relatively safe
-can cause liver toxicity with high doses, prolonged use or in alcoholics. Limit dose to 3-4 grams/day
opioids
-Opium – extracts of opium poppy. Morphine was isolated from opium in 19th century
-Opioid Receptors – members of G protein-coupled receptor family.
-Activation of receptor: inhibition of membrane depolarization
-Types of opioid receptors
-mu-1 and mu-2 – mediates most of effects of morphine and strong opioid agonists
-sigma
-delta
-epsilon
-kappa – mediates effects of mixed opioid agonist-antagonists -> limits addiction
-D. Endogenous opioid peptides
1. enkephalins – smaller peptides, release from neurons throughout entire pain axis
2. endorphins – larger peptides
3. dynorphins – larger peptides
types of opioids (Narcotics)
-1.Full agonists:
-strong agonists vs. moderate agonists
-can also be subdivided based on chemical structure class (useful to know in case patient has allergic-type reaction to one particular agent):
-Phenanthrenes; codeine, morphine, oxycodone, hydromorphone, levorphanol
-Phenylpiperidines: meperidine, fentanyl
-Diphenylheptanes: methadone, propoxyphene
-2. Mixed agonist antagonists
-3. Pure antagonists
-important bc if someone is allergic to codeine you can try fentanyl or methadone
effects of opioid agonists
-CNS effects
-Analgesia – alters perception of pain and pts reaction to pain!
-Dysphoria/euphoria – floating sensation, free from anxiety!
-Inhibition of cough reflex – used as antitussives! (codeine)
-Miosis (except meperidine causes mydriasis) “pinpoint pupils”!
-Physical dependence
-Respiratory Depression – dose-limiting factor! -> benzos are hard to OD on bc of this
-Sedation – causes drowsiness and impairs thinking!
-CVS effects
-decrease myocardial oxygen demand
-vasodilation & hypotension
-GI/biliary effects
-Constipation – !due to decreased motility and HCl secretion. Tx/prevent with laxatives and stool softeners!
-Increased biliary sphincter tone & pressure – gall stones!
-Nausea and vomiting !stimulates CTZ!
-Genitourinary effects
-Increased bladder sphincter tone
-Prolongation of labor
-Urinary retention
-Neuroendocrine system effects
-Inhibition of release of LH & FSH – !decrease ovarian and testicular fn!
-Stimulation of release of ADH and prolactin
-Immune system effects
-Suppression of function of natural killer cells
-Dermal effects
-Flushing
-Pruritis
-Urticaria (hives) or other rash
therapeutic uses of opioids
-analgesics
-acute myocardial infarction (for pain and anxiety)
-antitussives
-Tx of acute pulmonary edema
-antidiarrheals
-adjunct to anesthesia (given in combo with anticholinergic prior to surgery. Anticholinergic will decrease tracheal and bronchial secretions)
contraindications and precaution for opioids
-Contraindications for Opioid Use:
-Severe respiratory depression – can get respiratory failure!
-acute/severe asthma – b/c of respirator depression!
-increased ICP
-SR products if GI obstruction
-Precautions for Opioid Use::
-Avoid mixed agonist/antagonist in pts on full agonists !May precipitate withdrawal syndrome! -> limiting
-Head injuries
-Pregnancy (Chronic use during pregnancy may result in a dependent offspring)
-if underlying respiratory dysfunction, respiratory failure can occur
-Half-lives increased in patients with hepatic or renal dysfunction
-ADRs:
-Tolerance – usually after 2-3 weeks of nl therapy!!
-Physical dependence - after few weeks w/ withdrawal symptoms if drug abruptly d/c
-Psychologic dependence
-Constipation - !non pharm prevention!! Fluids and exercise!
-Prevention: Docusate + Senna or Bisacodyl PO
-can cause straining -> tear sutures -> observe in hospital
-Tx: MOM, Lactulose, Magnesium Citrate, Bisacodyl suppositories, phosphate soda enemas
-N/V – Can use metoclopramide, odensetron, prochlorperazine or trimethobenzamide short term.
-Respiratory depression – usually develop tolerance. With overdose -> pinpoint pupils -> Treat w/ naloxone (opioid antagonist)
-sedation, confusion, dizziness – usually with initiation or with dose increases. May last 2-3 days or until dose decreased -> tolerance should develop.
-Itching – occurs secondary to histamine release.
-hallucinations: rare
strong opioid agonists
-becomes cat D with prolonged use or high doses at term
-Used for mod - severe pain
-Dosing – no ceiling dose, no max dose
-Depending on agent being used - can be given PO, PR, SL, Buccal, IV, IM,SC, spinally (epidural and intrathecal) and transdermal.
-Controlled Substance category CII
-morphine
-methadone
-oxycodone
-fentanyl
-hydromorphone
-meperidine
-tapentadol
moderate opioid agonists
-Less potent than strong opioid agonists
-Do not produce max analgesia at doses that are well tolerated -> therefore given in submaximul doses for tx of mild-moderate pain and given in conjunction with non-opioid analgesic like aspirin or acetaminophen to enhance effects.
-Remember to monitor total dose of non-opioid analgesic as well. (i.e. APAP should be less than 3-4 grams/day)
-codeine
-codeine with APAP
-hydrocodone/APAP
-oxycodone/APAP
-oxycodone/ASA
-tramadol
morphine
-INJ (IV/IM/SC), PO, PR
-Principal alkaloid of opium poppy
-Kinetics – well absorbed PO, but -> significant first pass -> Need higher doses PO
-INJ:PO ratio is 1:6 or 1:3 w/ chronic use -> 6x higher dose for oral compared to INJ
-Indications – GOLD STANDARD -> DOC for cancer pain
-Also used for severe pain assoc w/ trauma and MI
-INJ (IV/IM/SC) – in several doses
-Epidural or intrathecal – must use preservative-free IV solutions (Duramorph) to prepare
-PO – (MS Contin, Kadian, Avinza) – long acting or sustained release
-PO – (MSIR) – immediate release, short acting, used PRN for breakthrough pain in combo with MS Contin around the clock
-PO solution immediate release – comes generic in various concentrations (10mg/5ml, 20mg/5ml or 20mg/ml) and brand name Roxanol (20mg/ml or 100mg/5ml). Caution when prescribing and administering
-Suppository immediate release – (RMS) 5mg, 10mg, 20mg, 30mg
-Dosing in cancer – use around the clock (ATC) w/ long acting form and PRN for breakthrough pain with immediate release
-PRN total daily dose should be half total daily dose of ATC regimen
-Ex. MS Contin 200mg Q 8 hrs (total dose 600mg/day) & Morphine Sulfate Immediate Release 60mg q 4h prn, MDD 5/day (300mg/day) -> 900mg a day
-Advantages: lots of dosage forms available, easy to titrate, generics available, easy conversion from IV to PO
-Disadvantage: M6 active metabolite – Can cause excessive sedation
methadone
-PO, INJ
-Low TI
-Used for pain but more for detox and maintenance tx of opiate dependence (heroin addiction)
-must closely monitor inventory and observe pt taking drug!
-use liquid form so pt can not cheek drug!
-never trust methadone pt telling you their dose -> give small amount and give rest of dose once confirmed
-Advantages:
-inexpensive, no active metabolite -> good in renal/hepatic dysfunction
-Use in morphine allergy
-Disadvantage:
-Difficult dosing/titration: Long half life for euphoric affect, but analgesic effect is 4-8 hours
-Titrate dose q5-7 days
-!!!Usually administered as q8h but can give extra dose for breakthrough pain -> usually ends up QID drug.
-Conversion more complex b/c cross tolerance is incomplete, will explain when go over charts!!!
oxycodone
-PO
-Available immediate release as tabs or oral solution. Also available as controlled/sustained release (Oxycontin).
-When given alone, considered strong agonist, when combined with APAP as in Percocet, can be used for mild-moderate pain although still CII controlled drug
-Advantages: no active metabolite !good in elderly or renal dysfunction!
-Disadvantages: no IV form
fentanyl
-INJ, transdermal patch, buccal-oral lozenge/lollipop
-Used for pain control and as adjunct to regional and general anesthesia!
-Oral Transmucosal Fentanyl Citrate (Actiq)- lollipop -> good if cant swallow
-Used for management of breakthrough cancer pain in pts with cancer who already have opioid therapy and are tolerant
-Advantage: Rapid onset. Good if can not swallow tabs. Can use if “morphine” allergy.
-Disadvantage: Expensive, short doa, accidental poisonings in kids
-Transdermal system:
-Good for chronic pain management
-Start w/ 25mcg/hr patch if no previous opiate use, otherwise use conversion chart
-Patch changed every 3 days -> Some patients require every 2 days!!
-conversion from morphine to transdermal fentanyl (Fentanyl dose in mcg/hr = ½ total daily dose of morphine PO)
-Advantages: Can use in morphine allergy. Less constipation than PO narcotics. Good if patients are NPO or if have severe stomatitis
-Disadvantages: Hard to titrate, Onset is 12 hours.
hydromorphone
-PO, PR, INJ
-very potent
-often used as PCA pump (pt controlled)
-advantages- less ADRs when used as epidural
-post op
-very well tolerate
-high addiction risk!
meperidine
-PO, INJ
-Not recommended for cancer pts b/c of short analgesic half-life of 3 hrs and irritates tissue -> can cause severe muscle fibrosis
-No long acting form available.
-Metabolite-Normeperidine has seizure activity and may cause neurological adverse effects
-!!!Can get grand mal seizures.
-!!!Metabolite has longer half life than parent compound -> stay in body longer than analgesic activity
-!!Metabolite excreted via kidney -> accumulates if renal dyfunction -!!!Hydroxyzine and promethazine may increase risk of neurological effects
-use within 14 days of MAOI (Tranylcypromine, Phenelzine, Isocarboxazid) -> life-threatening DDI like HTN crisis -> !!!(severe h/a, palpitations, n/v, sweating, choking sensation, increased temp, agitation, shivering, visual disturbances) !!!!
-Tachycardia or bradycardia and chest pain may occur
-Intracranial hemorrhage has also been reported
-NOT REALLY USED BC METABOLITES
tapentadol
-PO
-Unique MOA – mu receptor agonist and NE reuptake inhibitor
-Similar to tramadol but more potent and CII controlled substance. Used for moderate to severe pain
-Analgesic Potency similar to oxycodone, but with less GI ADRs
-Precautions: Similar to other opioids. Also - Seizures, Serotonin Syndrome
codeine
-PO, INJ
-C-II
-Better bioavailabilty than morphine
-!!Metab to morphine but has more ADRs. Used still b/c can call it in as verbal order w/ 6mo supply!!
-Good choice for anti-tussive
-Codeine w/ APAP (PO) (CIII or CV if liquid form)
-Tylenol #2 – 15mg codeine
-Tylenol #3 – 30mg codeine
-Tylenol #4 – 60mg codeine
(all have 300 or 325 mg APAP)
hydrocodone/APAP
-vicodin (C-III)
-not available alone!!
-good for moderate pain but not severe pain bc dose is limited by APAP content!!
equianalgesic dose conversions
-30mg of oral morphine what is hydromorphone dose 3 of hydromorphone
-90mg of morphine -> need higher dose of methadone
-doesnt want us to memorize ? -> but will ask on the test ? -> chart given??
NSAIDS MOA
-Inhibit prostaglandin (PG) synthesis from arachidonic acid by inhibiting the enzyme cyclooxygenase (COX)
-NSAIDS are nonselective -> they affect both COX 1 and 2
-COX-1
-Always present (constitutive) in various tissues
-Involved in synthesis of cytoprotective PGs (in GI tract)
-Catalyzes the formation of TXA2 (platelet aggregation and hemostasis)
-COX-2
-Levels normally low, induced via inflammation
-NOT involved in synthesis of cytoprotective GI protaglandins -> COX2 inhibitor less likely to cause GI bleeds and PUD
-Catalyzes the formation of Prostacyclin (antithrombotic)
-May also inhibit B and T cell proliferation by mechanisms not involving COX and PG formation
tylenol toxicity
-One of MC drugs involved in suicide attempt and accidental poisonings
-How much is an overdose?
-Depends on patient
-100-200 mg/kg (kids) or 7 g (adult) is considered potentially toxic
-Mechanism of Tylenol Toxicity: image
-Initial symptoms are mild and nonspecific -> asymptomatic or GI upset
-24-36 hours after ingestion:
-Increased LFTs
-hypoprothrombinemia
-Severe cases: liver failure, hepatic encephalopathy, death
-Tx of Tylenol Toxicity
-Measurement of serum acetaminophen levels
-IF level > 150-200 mg/L after 4 hours – increase risk of liver injury
-Antidote: N-acetylcysteine (NAC) Dose: loading dose of 140 mg/kg followed by 70 mg/kg q4h for 17 doses
acute vs chronic pain strat
