Chp 10 Analgesic Drugs Flashcards
Analgesics
medications that relieve pain without causing loss of consciousness (painkillers)
Opioid analgesics
synthetic drugs that bind to opiate receptors to relieve pain
Adjuvant analgesic drugs
drugs that are added for combined therapy with a primary drug and may have additive or independent analgesic properties, or both.
Pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage.
Opioids
a class of synthetic drugs used to treat pain that bind to the opiate receptors (often interchangeable with the term narcotic).
Nociception
processing of pain signals in the brain that giv es rise to the feeling of pain
When do you know if a patient has pain and how bad it is?
Pain exists when the patient says it does and is whatever the patient says it is (a personal and individual experience)
Nociceptors
a subclass of sensory nerves (A and C fibers) that transmit pain signals to the central nervous system form other body parts.
What is the relationship between nociceptors and nociception?
Pain results from stimulation of sensory nerve fibers called nociceptors. These receptors transmit pain signals from various body regions to the spinal cord and brain, which leads to the sensation of pain, or nociception.
What are the four processes of nociception?
- Transduction
- Transmission
- Perception of Pain
- Modulation
What happens during transduction?
- Injured tissue releases chemicals that propagate pain message.
- Action potential moves along an afferent fiber to the spinal cord.
What happens during Transmission?
- The pain impulse moves from the spinal cord to the brain
What happens during modulation?
- Neurons from brain stem release neurotransmitters that block the pain impulse
Pain threshold
the level of a stimulus that results in the sensation of pain (a measure of the physiologic response of the nervous system.)
Pain tolerance
the amount of pain a patient can endure without it interfering with normal function (the psychologic element,or subjective response, of pain.)
What circumstances can cause ones pain tolerance to vary from another person?
attitude
environment
culture
ethnicity
Acute pain
pain that is sudden in onset, usually subsides when treated, and typically occurs over less than a 6-week period
Chronic pain
persistent or recurring pain that is often difficult to treat. Includes any pain lasting longer than 3 to 6 months, pain lasting longer than 1 month after healing.
Somatic pain
pain that originates form skeletal muscles, ligaments, or joints.
Visceral pain
pain that originates from organs or smooth muscles
Superficial pain
pain that originates from the skin or mucous membranes; opposite of deep pain
Deep pain
pain that occurs in tissues below skin level; opposite of superficial pain.
Vascular pain
pain that results from pathology of the vascular or perivascular tissues
Referred pain
pain occurring in an area away from the organ of origin
Neuropathic pain
pain that results from a disturbance of function in a nerve
Phantom pain
pain experienced in the area of a body part that has been surgically or traumatically removed.
Cancer pain
pain resulting form any of a variety of causes related to cancer and/or the metastasis of cancer
Central pain
pain resulting from any disorder that causes central nervous system damage
Gate Theory
the most well described theory of pain transmission and pain relief. It uses a gate model to explain how impulses from damaged tissues are sensed in the brain.
During pain transmission what are several substances released when tissue is injured?
Bradykinin Histamine Potassium Prostaglandins Serotonin
What do the substances released when tissue is injured do in the pain transmission theory?
stimulate nerve endings, starting the pain process
initiates action potentials, electrical nerve impulses
How do some current pain medications work?
by altering the actions and levels of the substances released by injured cells (i.e. NSAIDs -> prostaglandins; antidepressants -> serotonin)
During pain transmission, where do the nerve impulses go once activated?
they enter the spinal cord and travel up to the brain
Where are the “gates” that are referred to in the Gate Theory located and what do they do?
in the dorsal horn which is the point of spinal cord entry.
the gate regulates the flow of sensory impulses to the brain.
What are the characteristics of and type of pain associated with A nerve fibers?
Large nerve fibers with a myelin sheath; Fast conduction speed; Sharp, well localized pain
What are the characteristics of and type of pain associated with C nerve fibers?
Small nerve fibers without a myelin sheath; Slow conduction speed; Dull, nonlocalized pain
The closing of the “gate” is affected by the activation of which fibers?
A fibers
The opening of the gate is affected by the stimulation of which fibers?
C fibers
What must happen in order for there to be pain perception?
The impulses must rise above the threshold of the cells that control the “gate” in order to pass through and travel up to the brain.
What are the body’s endogenous neurotransmitters and what do they do?
enkephalins and endorphins are produced within the body to fight pain and are considered the body’s painkillers.
How do enkephalins and endorphins work?
they bind to opioid receptors and inhibit the transmission of pain impulses by closing the spinal cord gates (similar to that of opioid analgesic drugs)
How does rubbing a painful area with massage or liniment help reduce pain?
When an area is rubbed, large sensory A nerve fibers from peripheral receptors carry pain-modulating impulses to the spinal cord. The A fibers tend to close the gate, which reduces pain sensation in the brain.
opioid tolerance
a normal physiologic condition that results from long-term opioid use, in which larger doses of opioids are required to maintain the same level of analgesia and in which abrupt discontinuation of the drug results in withdrawal symptoms
breakthrough pain
pain that occurs between doses of pain medication
synergistic effects
drug interactions in which the effect of a combination of two or more drugs with similar actions is greater than the sum of the individual effects of the same drugs given alone. For example, 1 + 1 is greater than 2.
PCA
patient-controlled analgesia - patients self administer pain meds such as morphine or hydromorphone via a PCA pump
PCA by proxy
administration of a PCA by another adult besides the patient
What is the purpose of using adjuvant drugs such as NSAIDs, antidepressants, anticonvulsants, and corticosteroids with opioids?
They produce a synergistic effect which allows for a lower dosage of opioids to be used reducing some of the adverse effects associated with opioids such as respiratory depression, constipation, and urinary retention.
What are some examples of adjuvant drugs for neuropathic pain?
amitriptyline (antidepressant
gabapentin or pregabalin (anticonvulsants)
opioid ceiling effect
drug reaches a maximum analgesic effect; analgesia does not improve, even with higher doses
agonist
a substance that binds to a receptor and causes a response (reduction of pain sensation)
agonists-antagonists (partial agonist)
substances that bind to a receptor and cause a partial response that is not as strong as that caused by an agonist
antagonist
a drug that binds to a receptor and prevents (blocks) a response
How does an antagonist drug work?
It binds to a pain receptor and exerts no response; acts as a competitive antagonist because it competes with and reverses the effects of agonist and agonist-antagonist drugs at the receptor sites.
Which receptors that opioids bind to are the most responsive to drug activity? which is most important?
mu, kappa, delta (mu is must important)
equianalgesia
the ability to provide equivalent pain relief by calculating dosages of different drugs and/or routes of administrations that provide comparable analgesia.
What is the main use and additional uses for opioid analgesics?
Main use: to alleviate moderate to severe pain
Additional uses: cough suppression, diarrhea, balanced anesthesia
What are some contraindications when using opioid analgesics?
drug allergy
severe asthma
Also use caution with patients with: respiratory insufficiency, elevated intracranial pressure, morbid obesity and/or sleep apnea, paralytic ileus, pregnancy
What are some adverse effects of opioid analgesics?
- CNS depression (most serious - leads to respiratory depression)
- nausea and vomiting
- urinary retention
- diaphoresis (sweating) and flushing
- pupil constriction (miosis)
- constipation
- itching
What is the difference between opioid physical dependence and psychologic dependence?
Physical dependence is the physiologic adaptation of the body to the presence of an opioid while psychologic dependence is 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.
What are naloxone (Narcan) and naltrexone (Revia) used for?
they are opioid antagonists that are used in the event of opioid overdose or in small doses to relieve itching associated with opioid use.
What are the symptoms of opioid withdrawal?
anxiety, irritability, chills and hot flashes, joint pain, lacrimation (tears), rhinorrhea (runny nose), diaphoresis (sweating), nausea, vomiting, abdominal cramps, diarrhea, confusion.
What substances interact with opioid analgesics?
Alcohol, antihistamines, barbiturates, benzodiazepines, monoamine oxidase inhibitors (all increase risk of respiratory depression)
Which nonopioid analgesic has little to no antiinflammatory effects?
tylenol (acetaminophen)
How does acetaminophen (tylenol) work?
similar to salicylates - it blocks peripheral pain impulses by inhibition of prostaglandin synthesis.
What is the maximum daily dosage of acetaminophen (tylenol) for healthy adults?
being lowered to 3000 mg/day
What is the maximum daily dosage of acetaminophen (tylenol) for elderly or those with liver disease?
2000 mg/day
When should acetaminophen not be taken?
in the presence of drug allergy, liver dysfunction, possible liver failure, G6PD deficiency (mostly found in males; leads to the destruction of red blood cells)
Why is it dangerous to take acetaminophen with alcohol?
alcohol is hepatotoxic so liver damage can be intensified
What are the overdose and toxicity problems associated with acetaminophen?
overdose is lethal.
overdose from chronic unintentional misuse causes liver and kidney damage
What is the recommended antidote for acetaminophen overdose?
acetylcysteine regimen
What is Feverfew?
An herbal substance related to the marigold family know for its antiinflammatory properties
What is Feverfew used for?
Used to treat migraine headaches, menstrual cramps, inflammation, and fever
What are adverse effects associated with Feverfew?
nausea, vomiting, constipation, diarrhea, altered taste sensations, muscle stiffness, and joint pain
What are some potential interactions with Feverfew?
may interact with aspirin and other NSAIDs, and anticoagulants
What is considered the fifth vital sign a nurse needs to assess?
pain
How might respiratory depression be manifested?
respiratory rate of less than 10 breaths/min, dyspnea (difficult or labored breathing), diminished breath sounds, or shallow breathing
