Analgesic Flashcards
Analgesics
Medications that relieve pain without causing loss of consciousness
“Painkillers”
Opioid analgesics
Adjuvant analgesic drugs
Pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
A personal and individual experience
Whatever the patient says it is
Exists when the patient says it exists
Nociception
Pain results:
These receptors transmit…
Pain results from stimulation of sensory nerve fibres called nociceptors.
These receptors transmit pain signals from various body regions to the spinal cord and brain.
Nociception 4 steps?
- Transduction: injured tissues release chemicals that propagate pain messages. Action potential moves along an afferent fibre to the spinal cord.
- Transmission: the pain impulse moves from the spinal cord to the brain
- Perception of pain
- Modulation: neurons from the brainstem release neurotransmitters that block the pain impulse
Pain Threshold
Level of stimulus needed to produce the perception of pain
A measure of the physiological response of the nervous system
Pain Tolerance
The amount of pain a person can endure without it interfering with normal function
Varies from person to person
Subjective response to pain, not a physiological function
Varies by attitude, personality, environment, culture, ethnicity
Classification of Pain by Onset and Duration
Acute pain
Persistent pain
Acute pain:
Sudden onset
Limited, has an end
Persistent pain (chronic pain):
Persistent or recurring
Lasts 3 to 6 months
More difficult to treat
Tolerance
Six Classification of Pain
Referred
Neuropathic
Phantom
Cancer
Central
Vascular
Gate Theory of Pain Transmission
Most common and well-described theory
Uses the analogy of a gate to describe how impulses from damaged tissues are sensed in the brain
Many current pain management strategies are aimed at altering this system.
Four Distinct Processes
Transduction
Transmission
Perception
Modulation
Transduction
Transformation of stimuli into electrochemical energy
Release of pain-medicating chemicals
Nociceptors
Pain Transduction
Tissue injury causes the release of the following:
These substances stimulate :
Tissue injury causes the release of the following:
Bradykinin
Histamine
Potassium
Prostaglandins
Serotonin
Substance P
They stimulate nerve endings, starting the pain process.
Pain Transduction
The nerve impulses enter the:
The point of spinal cord entry or the “gate” is the…
This gate regulates the?
The nerve impulses enter the spinal cord and travel up to the brain.
The point of spinal cord entry or the “gate” is the dorsal horn.
This gate regulates the flow of sensory impulses to the brain.
Pain Transduction
Closing the gate stops:
If no impulses are transmitted to higher centres in the brain, there is no?
Closing the gate stops the impulses.
If no impulses are transmitted to higher centres in the brain, there is no pain perception.
Pain Transmission
Two types of nociceptor pain fibres:
Large-diameter, A-delta fibres, and small-diameter C fibres
Pain Perception
Define
The larger the number of mu receptors, the
Subjective phenomenon of pain
——Identical stimulus can evoke different pain from one individual to another
“How it is felt”
Complex behavioural, psychological, and emotional factors
The number of mu receptors in the dorsal horn appear to play a crucial role in pain perception and emotional well-being
The larger the number of mu receptors , the less pain is perceived
Pain Modulation
Neural activity that controls pain transmission to neurons
Both peripheral and central nervous systems
Descending pain system
Enkephalins and endorphins
Massage
Massaging a painful area often reduces the pain.
Large sensory A nerve fibres inhibit impulse transmission
Close the gate
Treatment of Pain in Special Situations
Patient-controlled analgesia (PCA)
Patient comfort versus fear of drug addiction
Opioid tolerance
Use of placebos
Recognizing patients who are opioid tolerant
Breakthrough pain
Synergistic effects
Adjuvant Drugs
Examples
Drugs from chemical categories other than opioids
Assist primary drugs in relieving pain:
Nonsteroidal anti-inflammatory drugs (NSAIDs)
Antidepressants
Anticonvulsants
Corticosteroids
Example: adjuvant drugs for neuropathic pain
Amitriptyline (antidepressant)
Gabapentin or pregabalin (anticonvulsants)
World Health OrganizationThree-Step Analgesic Ladder
Step 1: Nonopioids with or without adjuvant medications after the pain has been identified and assessed. If pain persists or increases, treatment moves to:
Step 2: Opioids with or without nonopioids and with or without adjuvants. If pain persists or increases, management then rises to:
Step 3: Opioids indicated for moderate to severe pain, administered with or without nonopioids or adjuvant medications
Opioid Drugs
Synthetic drugs that bind to the opiate receptors to relieve pain
Opioid Drugs
Mild agonists:
codeine, hydrocodone
Opioid Drugs
Strong agonists
morphine, hydromorphone hydrochloride, oxycodone, meperidine, fentanyl, methadone
Opioid Drugs
Meperidine
not recommended for long-term use because of the accumulation of a neurotoxic metabolite, normeperidine, which can cause seizures.
Opioid Ceiling Effect
Drug reaches a maximum analgesic effect.
Analgesia does not improve, even with higher doses.
-Codeine phosphate
-Pentazocine
-Nalbuphine
Opioid Analgesics
Three classifications based on their actions:
Agonists
Agonists–antagonists
Antagonists (nonanalgesic)
Agonists
Bind to an opioid pain receptor in the brain
Cause an analgesic response (reduction of pain sensation)
Agonists–Antagonists
Binds to a pain receptor and causes a weaker pain response than full agonists
kappa (k) or mu opioid receptors
Also called partial agonists or mixed agonists
used in pts who are addicted to opioids and in obstretical pts (avoid oversedation of mom and fetus)
Antagonists
Reverse the effects of opioids on pain receptors
Bind to pain receptors and exert no response
Also known as competitive antagonists
Equianalgesia
Ability to provide equivalent pain relief by
-calculating dosages of different drugs or
-routes of administration that provide comparable analgesia
Examples: morphine, hydromorphone, oxycodone, hydrocodone bitartrate, fentanyl
Continuous release vs. immediate release formulations
Opioid Analgesics:Indications
Mainly used to alleviate moderate to severe pain
Often first line agents analgesic in immediate post operative setting
Often given with adjuvant analgesic drugs to assist primary drugs with pain relief
Balanced anaesthesia
Opioids are also used for:
Cough centre suppression
Treatment of diarrhea
Opioid Analgesics: Contraindications
Use with extreme caution in patients with the following:
Known drug allergy
Severe asthma
Respiratory insufficiency
Elevated intracranial pressure
Morbid obesity or sleep apnea
Paralytic ileus
Pregnancy
Opioid Analgesics: Adverse Effects
Central nervous system (CNS) depression
-Leads to respiratory depression
-Most serious adverse effect
Nausea, vomiting, constipation, biliary tract spasm
Urinary retention
Hypotension, palpitations, flushing
Itching, rash, wheal formation
Pinpoint pupils indicating a possible overdose
Opioids: Opioid Tolerance
A common physiological result of chronic opioid treatment
State of adaptation
Result: larger dose is required to maintain the same level of analgesia
Opioids: Physical Dependence
Physiological adaptation of the body to the presence of an opioid
Opioid tolerance and physical dependence are expected with long-term opioid treatment and should not be confused with psychological dependence (addiction).
Opioids: Psychological Dependence
Addiction?
Addiction: a pattern of compulsive drug use characterized by a continued craving for an opioid and the need to use the opioid for effects other than pain relief
Opioid Analgesics: Toxicity and Management of Overdose
Naloxone hydrochloride
Naltrexone (ReVia®)
Regardless of withdrawal symptoms, when a patient experiences severe respiratory depression, an opioid antagonist should be given.
Naloxone reversing an overdose
Naloxone has a stronger affinity to opioid receptors than opioids, such as heroin or oxycodone, so it knocks the opioids off the receptors for a short time (30 to 90 minutes). This allows the person to breathe again and reverse the overdose.
Toxicity and Management of Overdose
Opioid withdrawal or opioid abstinence syndrome
Occur in 2 weeks in opioid-naïve patients
Gradual dosage reduction after chronic opioid use
Opioid Analgesics: Interactions
Alcohol
Antihistamines
Barbiturates
Benzodiazepines
Promethazine
Monoamine oxidase inhibitors
Others
Codeine Sulphate
Natural opiate alkaloid
(Schedule I) obtained from opium
Less effective
Ceiling effect
More commonly used as an
antitussive drug
Gastrointestinal (GI) disturbance
Fentanyl
Synthetic opioid (Schedule I) used to treat moderate to severe pain
Parenteral injections, transdermal patches (Duragesic Mat®), sublingual effervescent tablet (Fentora®)
Dilaudid
Hydromorphone (Dilaudid®): very potent opioid analgesic; Schedule I drug
1 mg of (IV) or (IM) hydromorphone is equivalent to 7 mg of morphine.
Methadone Hydrochloride
Synthetic opioid analgesic (Schedule I)
Opioid of choice for detoxification treatment of opioid addicts in methadone maintenance programs
Renewed interest in the use of methadone for chronic (e.g., neuropathic) and cancer-related pain
Prolonged half-life of the drug: cause of unintentional overdoses and deaths
Cardiac dysrhythmias
Morphine Sulphate
Naturally occurring alkaloid derived from the opium poppy
Drug prototype for all opioid drugs; Schedule I controlled substance
Indication: severe pain
Oral, injectable, and rectal dosage forms; also extended-release forms
Oxycodone Hydrochloride
Structured similar to morphine
Synthetic opioid
Often combined with acetaminophen (Percocet tablets: typical is 325 mg acetaminophen and 5 mg of oxycodone)
Naloxone Hydrochloride (Narcan®)
Pure opioid antagonist
Drug of choice for the complete or partial reversal of opioid-induced respiratory depression
Indicated in cases of suspected acute opioid overdose
Failure of the drug to significantly reverse the effects of the presumed opioid overdose indicates that the condition may not be related to opioid overdose.
Nonopioid Analgesics:Acetaminophen (Tylenol®)
Analgesic and antipyretic effects
Little to no anti-inflammatory effects
Available over the counter (OTC) and in combination products with opioids
Acetaminophen: Mechanism of Action
Similar to that of salicylates
Blocks pain impulses peripherally by inhibiting prostaglandin synthesis
Acetaminophen: Indications
Mild to moderate pain
Fever
Inability to take aspirin products
Acetaminophen: Dosage
Maximum daily dose for healthy adults is 4 g/day, but Health Canada is considering lowering*
—-2 000 mg for older adults and those with liver disease
Inadvertent excessive doses may occur when different combination drug products are taken together.
Be aware of the acetaminophen content of all medications taken by the patient (OTC and prescription).
*Note: As of the date of writing of this text, Health Canada had not yet made this decision.
Acetaminophen: Contraindications and Interactions
Should not be taken in the presence of following:
Drug allergy
Liver dysfunction
Possible liver failure
G6PD deficiency
Dangerous interactions may occur if taken with alcohol or other drugs that are hepatotoxic.
Acetaminophen: Toxicity and Managing Overdose
Even though available OTC, lethal when overdosed
Overdose, whether intentional or resulting from chronic unintentional misuse, causes hepatic necrosis: hepatotoxicity.
Long-term ingestion of large doses also causes nephropathy.
Recommended antidote: acetylcysteine regimen
Miscellaneous Analgesic:Tramadol Hydrochloride
Central acting analgesic
Treatment of moderate to moderately severe pain
Potential adverse effects: seizures (with excess dosages) and serotonin syndrome (if taken with SSRIs)
Frequently combined with acetaminophen (Tramacet)
Herbal Products: Feverfew
Related to the marigold family
Anti-inflammatory properties
Used to treat migraine headaches, menstrual cramps, inflammation, and fever
May cause GI distress, altered taste, muscle stiffness, joint pain
May interact with aspirin and other NSAIDs, as well as anticoagulants
Analgesics:Nursing Implications
Before beginning therapy, perform a thorough history regarding allergies and use of other medications, including alcohol, health history, and medical history.
Obtain baseline vital signs, intake and output.
Assess for potential contraindications and drug interactions.
Perform a thorough pain assessment, including pain intensity and character, onset, location, description, precipitating and relieving factors, type, remedies, and other pain treatments.
—Level of pain is now considered a “fifth vital sign.”
—Rate pain on a 0–10 or similar scale.
Be sure to medicate patients before the pain becomes severe, so as to provide adequate analgesia and pain control.
Pain management includes pharmacological and nonpharmacological approaches; be sure to include other interventions as indicated.
Patients should not take other medications or OTC preparations without checking with their physicians.
Instruct patients to notify physician about signs of allergic reaction or adverse effects.
Opioid Analgesics:Nursing Implications
Oral forms should be taken with food to minimize gastric upset.
Ensure safety measures, such as keeping side rails up, to prevent injury.
Withhold dose and contact physician if there is a decline in the patient’s condition or if vital signs are abnormal, especially if respiratory rate is less than 10 breaths/min.
Check dosages carefully.
—Follow proper administration guidelines for IM injections, including site rotation.
—Follow proper guidelines for IV administration, including dilution, rate of administration, etc.
Constipation is a common adverse effect and may be prevented with adequate fluid and fibre intake.
Instruct patients to follow directions for administration carefully and to keep a record of their pain experience and response to treatments.
Patients should be instructed to change positions slowly to prevent possible orthostatic hypotension.
Monitor for adverse effects
—Contact physician immediately if the patient’s vital signs change, condition declines, or pain continues.
—Respiratory depression may be manifested by a respiratory rate of less than 10 breaths/min, dyspnea, diminished breath sounds, or shallow breathing.
Opioid Analgesics: Nursing Implications
Monitor for therapeutic effects.
Decreased perception of pain
Decreased severity of pain
Increased periods of comfort
Improved activities of daily living, appetite, and sense of well-being
Decreased fever (acetaminophen)
Notes
opioids- decrease LOC, respirations
pain- is whatever the pt says it is
visceral- organs
somatic- bone, tendons, and muscle, skin
(stimulation of sensory nerve fibres-pain)
Pain threshold
pain tolerance- the amount of pain a person can endure
Neuropathic- nerve pain (diabetes)
gallbladder pain- left side (pain in shoulder/ back/ scapula- referred pain)
phantom pain- damage to BVs and nerves- amputation- still feel the pain
Cancer pain- pressure from the tumours on organs/ tissues
Central- stroke, MS, cancer
Vascular pain- migraine
PhysioMCST-phases nociceptive pain (video)
Transduction-release of chemical picked up by Rs, nerve impulse to the brain
Transmission- fibres activate R in brain
Perception- subjective phenomenon, stimulus can be provoked differently
Modulation- neural 1 activity, control pain transmission
PCA-self medicate, hooked up to an IV for pain
Breakthrough pain they can’t wait for another drug to kick in, so we give them something short-acting
Opioid- respiratory depression
ANGINA- forms lactic acid because it does not get enough oxygen
itch- common AE OF OPIOID
Adjuvant
2 Medications
assist primary drugs (opioids)
Amitriptyline (antidepressant)
Gabapentin/ pregabalin (diabetic neuropathy)
Opioids
Mild agonists
codeine (affected by opioid ceiling effect)
hydrocodone
Meperidine
not recommended
Agonits drugs examples
morphine, codeine, methadone, fentanyl
Agonist-antagonists
pentazocine
weaker pain response
partial agonists
Antagonists
Narcan
reverse effects of opioids
vitals of most concern for a pt taking Dilaudid?
respirations (ABCs)
