Pain and Analgesic Drugs Flashcards
What is Nociception?
Detection of noxious stimuli or stimuli that are capable of damaging tissue
What is pain?
Unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
What are the four processes of pain?
Transduction
Transmission
Perception
Modulation
What is acute pain?
Sudden onset
Usually subsides once treated
What is an example of a nociceptive stiumulus?
Stepping on a nail
Causes acute pain via activation of nociceptive pathways
What is chronic pain?
Persistent or recurring pain
-More than 6 weeks
Difficult to treat
Examples of chronic pain?
Mild, musculoskeletal pain
Deep pain
Neuropathic pain
Chronic pain of indeterminate cause
What is neuropathic pain?
Pain induced by injury or disease of the somatosensory system
What causes neuropathic pain?
nerve injury
Infections of the NS
e.g, phantom limb pain, trigeminal neuralgia, shingles (postherpetic neuralgia), diabetic neuropathy
How does neuropathic pain develop?
Slowly
outlasts healing of original injury
Examples of neuropathic pain?
Allodynia
Hyperalgesia
Causalgia (burning)
What are some sources of pain?
Somatic (superficial)
Visceral (vascular, respiratory)
Referred
Cancer (breakthrough)
Phantom
Neuropathic
Psychogenic
Central
What are the two groups of pain medications?
Analgesic
Anesthetic
What do analgesic pain medications do?
Selectively blocks the sensation of pain without
blocking other symptoms or loss of consciousness
What do local anesthetic pain medications do?
Blocks nerve conduction and all local sensations (including pain)
What do general anesthetic pain medications do?
Cause loss of sensations and unconsciousness
Where is the site of action of opioids?
Higher centres
Spinal cord
What do opioids alter in higher centres in the brain?
Psychological response to pain
-Pain can still be felt but produces less suffering
-Changes perception
What do opioids do in the spinal cord?
Reduce neurotransmitter release from terminals pain fibres in dorsal horn of spinal cord
-Modulation
How do opioids work?
The drugs bind to opioid receptors
What is an opiate?
Any drug derived from opium
e.g, Morphine, codeine
What is opium?
βjuiceβ of the poppy (Papaver somniferum)
Why do different opioids have different properties?
They have various affinity and activation for different opioid receptor subtypes
and pharmacokinetic differences
All opioid analgesics are what?
Full agonists of partial agonists at Β΅ and/or ΞΊ receptors
What are the kinds of opioid receptors?
Β΅ (mu) receptors
ΞΊ (kappa) receptors
Ξ΄ (delta) receptors
Β΅ (mu) receptors
Analgesia
Brain and spinal cord
Which parts of the brain have Β΅ (mu) receptors?
Cortex, medulla, thalamus, limbic system, amygdala
ΞΊ (kappa) receptors
Analgesia
Brain and spinal cord
-Dysphoria and hallucinations
What are the pharmacological properties of opioids?
Analgesia
Sedation and mental clouding
Euphoria and tranquility
Antitussive -no cough reflex
Depression of respiratory centre
Nausea, vomiting
Miosis (pin point pupil)
Tolerance, serious dependence
Constipation
Postural hypotension
Dilation of cutaneous blood vessels, warm skin
Urinary urgency but difficult urination
Biliary colic and epigastric distress
Which pharmacological properties of opioids are associated with Β΅ (mu) receptors?
Analgesia (and kappa)
Euphoria and tranquility (and delta)
Depression of respiratory centre
Miosis (pin point pupil) (and kappa)
Tolerance, serious dependence
Constipation (and delta)
Examples of opioid analgesics?
Morphine
Methadone (longer action than morphine)
Fentanyl
Diamorphine (Heroin)
Levorphanol
Hydromorphone
Oxycodone
Codeine
What are opioids used for?
Alleviate mild, moderate to severe pain (depends on opioid or given with adjuvant agent to relieve pain)
Cough centre suppression
Treatment of diarrhea
Balanced anaesthesia
What opioid suppresses cough centre?
Codiene
What opioid is used for the treatment of diarrhea?
Loperamide
What opioid is used to balance anasthesia?
Fentanyl
What is morphine used for?
Acute and chronic pain
What drug are other analgesics often compared to?
Morphine
it is the standard
Equianalgesic doses
Which receptors does morphine mostly bind to?
mu-opioid receptors in the brain and spinal cord
How is morphine administered?
IV, IM, SC, PO, intrathecal
What is half-life (T 1/2) of morphine?
2-4 hours
Where is morphine metabolized?
Extensive liver metabolism
-First-pass metabolism
-Inactivation
-Liver disease
What happens if morphine is used during pregnancy?
Dependance, crosses placenta
What happens if morphine is used while breastfeeding?
Enters breast milk
What is breakthrough pain?
Transient episodes of pain, while chronic pain is controlled
Requires access to rescue medication
How is cancer pain treated?
Sustained release morphine (MS Contin) Around The Clock (ATC)
NSAIDs
Adjuvants
Other analgesics when needed
How is MS Contin administered?
PO
What is MS Contin?
MS = morphine sulfate
Contin = continuous/sustained release
What is the most common non-narcotic analgesic?
NSAIDs
What are some examples of adjuvants?
Antidepressants eg amitriptyline (Elavil)
Antiseizure drugs eg carbamazepine
Glucocorticoids
When is morphine use contraindicated or should be used very cautiously?
Severe asthma or other respiratory insufficiency
- causes RESPIRATORY depression
Hepatic dysfunction
Elevated intracranial pressure (ICP) β exacerbates it
Pregnancy
What is the #1 serious adverse effect associated with opioids?
Respiratory depression
What other adverse effects are associated with opioid analgesics?
CNS depression (could lead to coma)
Nausea and vomiting
Constipation
Hypotension
Histamine release
Urinary retention
Diaphoresis and flushing
Pupil constriction (miosis)
When is nausea and vomiting caused by opioids greatest?
On 1st dose then decreases
Why do opioids cause hypotension?
Cause dilation of peripheral arteries and veins (histamine release)
What happens because of histamine release associated with opioid use?
Itchiness
Rash
Dilation of peripheral arteries and veins
What other drugs do opioids have cumulative effects with?
CNS depressents
e.g, antipsychotics, antihistamines, sedatives (benzodiazepines, barbiturates)
Ethanol (alcohol)
What are some moderate opioids?
Codeine (3-methylmorphine)
Oxycodone
Buprenorphine
Codiene
What are properties of codiene?
Less analgesia and respiratory depression
Antitussive
Liver metabolism (~10% of oral dose) = unpredictable
Often combined
What is Codiene often combined with?
Acetaminophen in Tylenol 1, 2 and #
Acetylsalicylic acid in 222βs or 292
What is required for the activation of Oxycodone?
Metabolism
What is there potential for with oxycodone use?
Abuse (addiction)
What is oxycodone also kown as?
Oxycontin or Percodan
What is oxycodone widely used in combination with?
Acetaminophen ( aka percocet)
What are some opioid antagonists?
Naloxone (Narcan)
Naltrexone
What are opioid antagonists used for?
Complete or partial reversal of opioid induced respiratory depression
What is the half-life of Naloxone?
~2 hours
-Shoter half-life than morphine and other ropioids
How is Naloxone administered?
IV, IM, SC and nasal
What way is naloxone administered in rescue kits?
IV or nasal
How is opioid addiction treated?
Methadone program
Buprenorphine + nalosone (suboxone)
What is Buprenorphine + naloxone (suboxone)?
SL tablet
Alternative to methadone
-help you use other opioids less
What is a common physiological result of chronic opioid treatment?
Tolerance
What is opioid physical dependance?
State that develops in which an abstinence syndrome will occur if a drug is abruptly withdrawn
Drug must be administered to maintain normal function
Occurs with other unrelated drugs classes
On abrupt discontinuation or when an opioid
antagonist is administered
What is narcotic withdrawal?
Opioid abstinence syndrome
Unpleasant but not dangerous
What are withdrawal symptoms?
Anxiety
Irritability
Chills and hot flashes
Joint pain
Lacrimation
Sneezing
Rhinorrhea
Diaphoresis
Nausea
Vomiting
Abdominal cramps
Diarrhea
Physical dependence is NOT the same as what?
Addiction
What is addiction?
Substance dependence syndrome
What are both parts of the bodyβs response to the presence of opioid drugs?
Tolerance
Physical dependence
Oral opioids should be taken with what
Food
-minimize gastric upset
When should opioid dose be withheld, and physician should be contacted?
If there is a decline in the clientβs condition or is VS are abnormal
-Especially if respiratory rate is less than 12
How can respiratory depression caused by opioids manifest?
Less than 12 breaths per minute
Dyspnea
Diminished breath sounds
Shallow breathing
How can constipation caused by opioids be managed?
Take with adequate fluid and fibre intake
stool softener (docusate) and or stimulant (senna) daily
How can ortjostatic hypotension caused by opioids be managed?
Instruct to change positions slowly
