Pain, opioids, drug abuse
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define acute pain
- from illness or injury
- ends at some point, with or without medical treatment
what is the drug of choice to treat myocardial infarction?
define chronic pain
- persists >3 months
- persists >1 month after fixing acute tissue injury
- accompanies non-healing lesion
cardiovascular effects of uncontrolled pain
- increased heart rate
- vasoconstriction (systemic vascular resistance)
- increased BP
- increased myocardial oxygen consumption
- altered regional blood flow
- deep vein thrombosis
respiratory effects of uncontrolled pain
- decreased lung volumes
- decreased cough effort
- increased sputnum retention
effects of uncontrolled pain on GI tract
- decreased gastric/bowel motility
- urinary retention
psycho-neuro-endocrine effects of uncontrolled pain
- increase of epinephrine
- glucagon release -> increased glucose levels -> healing prolonged and increased risk of infection
- anxiety, fear, sleeplessness
what are adjuvants?
- any non-pharm method for controlling pain
- examples: elevation/positioning, ice, heat, distraction, etc.
what are the WHO's 3 steps in approaching chronic pain?
- 1. Non-opioid +/ adjuvant
- 2. opioid +/ non-opioid +/ adjuvant
- 3. opioid +/ non-opioid +/ adjuvant
between steps 2 and 3, change (usually increase) dose of opioid
what kind of analgesic does not have a dose ceiling?
3 opioid receptors
- Mu- most common
- Kappa - weak, involved with agonist-antagonists
- Delta - don't interact with opioid analgesics
effects of mu activation by opioids
- respiratory depression
- cough suppression
- orthostatic hypotension
what is the most commonly used opioid (agonist)?
what three actions of morphine help manage pain?
- 1) reduce perception of pain
- 2) psychological response to pain is reduced
- 3) induces sleep
true or false: morphine affects all the senses and causes loss of consiousness
false: does not affect other senses, does not cause loss of consciousness
morphine is most effective against what kind of pain?
- constant, dull pain
- moderate to severe
what can happen with prolonged use of morphine?
what is the main adverse effect you should be on the lookout for when administering morphine? who is most at risk?
- respiratory depression
- -opiate naive
- -compromised pulmonary status
- -neuromuscular disease
- -very old or very young
when should you titrate opioid doses?
- when they are not effective enough
- every 2 hours with short-acting agents
- until >50% reduction in pain
- when there is breakthrough pain or need a rescue dose
why does only a small amount of each dose of morphine actually produce analgesic effects?
- poor lipid solubility
- can't cross BBB easily
- only small fraction reaches CNS (needs to get to CNS to relieve pain)
should oral doses of morphine be larger or smaller than parenteral doses? why?
- first pass metabolism
methods of morphine administration
- intrathecal (injection into spinal cord)
how should you titrate opioid doses?
- small increments
- 25-100% of baseline dosage (based on pain rating)
True or false: Once opioid administration ends, all side effects also end.
False: respiratory depression lasts longer than analgesic effects, and longer than antagonist effects (i.e. when administering Narcan)
patient controlled analgesia
what should you do if a patient is opioid naive?
assess response to the first dose carefully
true or false: opioids always cause a drop in BP
false: if patient is well hydrated, BP should not drop
are opioids better tolerated when the patient is lying down (supine) or sitting up?
Supine: if upright, may cause nausea/vomiting, orthostatic hypotension/dizziness
- an opioid with rapid onset, short duration of action
- 100x more potent than morphine
- used for surgical anesthesia
true or false: as tolerance of opioids increases, tolerance of all side effects also increases
false: you will always be constipated
what are the withdrawal effects of opioids?
insomnia, pain, restlessness, increased GI activity
what should you know about meperidine (Demerol)?
- it is a BAD DRUG and you shouldn't use it!
- -> seizure risk
- -short half life
- -reacts poorly with other drugs
- -continued use can cause toxicity due to build up
when is meperidine ok to use?
- short term
- preferred for labor
- less likely to depress fetal respiration and uterine contractions
- -have naloxone on hand
what is codeine good for treating?
- mild to moderate pain
if opioids make a patient nauseous, what drug should you avoid giving them?
- causes more emesis
true or false: codeine is always an effective analgesic in all patients
false: some people lack the enzyme to convert it to morphine -> no analgesic effect
if codeine is an opioid, why might it have a dose ceiling?
often combined with other drugs like acetaminophen that do
if an agonist-antagonist is given along (not with a pure opioid agonist), what will the effect be? If taken with an agonist?
- alone: analgesia
- with agonist: antagonizes analgesia produced by agonist
what's Butorphanol? how does it interact with morphine?
- weak agonist at kappa
- antagonist at mu: kicks off morphine
- may cause withdrawal
- ae: risk fatal dysrhythmia
when should you give naloxone (Narcan)?
what is the goal?
mode of administration?
- opioid antagonist: give for opioid overdoses
- goal: stop respiratory depression
how should Narcan be administered (related to duration of action)? what can occur if administered incorrectly?
- short duration of action: small, repeated doses
- give too much -> withdrawal
drugs that relieve pain without causing loss of consciousness
general term for any drug, natural or synthetic, that has actions similar to those of morphine
term for a drug that may mean an analgesic, a CNS depressent, and/or any drug capable of causing physical dependence
a larger dose is required to produce the same response that could formerly be produced with a smaller dose
what is cross tolerance?
resistance to a medication as a result of tolerance to a pharmacologically similar drug
How should opioid administration be stopped?
gradually -> minimize withdrawal (abstinence syndrome)
what affect does regular use of opioids during pregnancy have?
physical dependence in fetus -> withdrawal after delivery
Three classic signs of opioid overdose:
- coma (profound- patient can't be aroused)
- respiratory depression
- pinpoint pupils (abnormally constricted pupils)
is it better to administer opioids on a fixed schedule, or PRN? why?
fixed schedule (breakthrough pain may be managed with additional rescue doses)
prevents needless discomfort, reduces patient anxiety related to pain
True or false: pharmaceutical scientists have produced new opioid analgesics that are superior to morphine due to their low potential for respiratory depression and abuse.
false: new opioid agonists have been created, but none are considered superior to morphine. All still have similar adverse effects.
similar pain relief to codeine
- most prescribed drug in US
- similar pain relief to codeine
- always combined with other drugs
define drug abuse
drug use that is inconsistent with medical or social norms
continued use of psychoactive substance despite physical, phsychologic or social harm
physical dependence is NOT the same as addiction
Is it common for patients to experience physical dependence when opioids are used short term for pain relief?
- No, rarely
- when physical dependence does occur, developing addictive behavior is also rare
what is the best way to minimize physical dependence and abuse of opioids?
administration of lowest effective dosages for shortest time needed
what is PCA?
- Patient Controlled Analgesia
- allows patient to self-administer opioids parenterally on PRN basis
who is a candidate for PCA?
- postoperative patients
- patients experiencing pain as a result of:
how is PCA controlled to prevent overdose?
- time control mechanisms
- limits dosage allowed per hour
- regulates minimum interval between doses
Why is PCA preferable to regular IM injections? (besides not having to get stuck with needles a bunch)
- provides more regular, small doses versus larger doses
- avoids peak/troughs, keeps plasma drug levels more steady
are opioids good for alleviating pain in head injuries?
- use with caution: head injuries can cause resp. depression and elevation of ICP
- opioids may exacerbate
why should you limit opioid use in cancer patients?
trick question! You shouldn't! They've got cancer, we're much more worried about that than them getting hooked on their meds. give them as much as they need to relieve the pain.
what are some guidelines for safely using opioids to treat non-cancer chronic pain?
- try non-opioids first
- discuss benefits and risks with patients
- try to use only one prescriber and one pharmacy
- comprehensive follow-ups
- stop if they don't work
- document everything
Intense, subjective need for a particular psychoactive drug
what is the reward circuit and what role does it play in drug addiction?
system in brain that normally reinforces behaviors that contribute to survival
addictive drugs activate reward circuit, release dopamine -> reward/reinforce drug use
what phenomenon occurs during synaptic remodeling in the brain with use of addictive drugs? how does this encourage addiction?
- 1) brain produces less dopamine
- 2) fewer dopamine receptors
- -> reduced response to drug, natural stimuli also can't activate circuit as well
- -> less pleasure from natural stimuli makes user depressed
what is the principal federal legislation addressing drug abuse?
- Controlled Substances Act
- (Comprehensive Drug Abuse Prevention and Control Act of 1970)
Under the Controlled Substances Act, drugs are assigned to one of five categories: Schedule I, II, III, IV, V. Drugs in which category have high potential for abuse and no approved medical use?
Drugs in Schedules II-V all have approved medical uses. What determines their assignment to each category?
potential for drug's abuse/ability to cause dependence
Of drugs with medical applications, drugs in which category (Schedule I-V) have the highest potential for abuse/dependence?
- Schedule II
- (Schedule I has no medical use)
What does the label on Schedule II-V drugs prohibit?
transferring of the drug to any person other than the patient for whom it was prescribed
what role do prostaglandins and substance P play in pain reception?
can enhance sensitivity of pain receptors to activation
what role do enkephalins and beta-endorphins play in pain reception?
- suppress pain conduction
- (endogenous opioid compounds)
pain that results from injury to tissues
- nociceptive pain
- -may be somatic or visceral
pain that results from injury to peripheral nerves
somatic pain v. visceral pain descriptions
- somatic: localized, sharp
- visceral: vaguely localized, diffuse/aching
neuropathic pain descriptions
burning, cold, shooting, jabbing, tearing, numb, dead
why can switching from one opioid to another be beneficial?
- different opioids have different side effects
- switching may decrease adverse effects while maintaining pain control
when can breakthrough pain occur and how does it develop?
- can occur any time in dosage schedule
- develops quickly, reaches peak intensity in minutes, may persist for hours
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