Opioid Analgesics & Pain Drug – Pharmacology

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Opioid Analgesics & Pain Drug – Pharmacology

This chapter of Pharmacology covers Opioid analgesics and pain drug.

Opioids: Psychologic Dependence

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

A patient who has metastasized bone cancer and therefore has been on transdermal fentanyl patches for pain management for 3 months. He has been hospitalized for tests and has told the nurse that his pain is becoming “unbearable.” The nurse is reluctant to give him the ordered pain medication because the nurse does not want the patient to get addicted to the medication. The nurse’s actions reflect

a.appropriate concern for the patient’s best welfare.
b.appropriate caution for a patient who is already on a long-term opioid.
c.an uncaring attitude toward the patient.
d. a failure to manage the patient’s pain properly.
Rationale: Patients with severe pain, including metastatic pain or bone pain, may need higher and higher doses of analgesics. The nurse is responsible for ensuring that the patient experiences adequate pain relief.

Opioid Analgesics:
Toxicity and Management of Overdose

-naloxone (Narcan)
-naltrexone (ReVia)
Regardless of withdrawal symptoms, when a patient experiences severe respiratory depression, an opioid antagonist should be given.

Toxicity and Management
 of Overdose

-Opioid withdrawal/opioid abstinence syndrome
-Manifested as:
>Anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea, and also confusion

Opioid Analgesics: Interactions

Also Monoamine oxidase inhibitors

Nonopioid Analgesics:
Acetaminophen (Tylenol)

-Analgesic and antipyretic effects
-Little to no antiinflammatory effects
-Available over the counter and also in combination products with opioids

Acetaminophen: Mechanism of Action

-Similar to salicylates
-As a result blocks pain impulses peripherally by inhibiting prostaglandin synthesis

Acetaminophen: Indications

-Mild to moderate pain
-Alternative for those who cannot take aspirin products

Acetaminophen: Dosage

-Maximum daily dose for healthy adults is being lowered to 3000 mg/day
>2000 mg for elderly or those with liver disease
-Inadvertent excessive doses may occur when different combination drug products are taken together
-Also be aware of the acetaminophen content of all medications taken by the patient (OTC and prescription)

Acetaminophen: Contraindications/Interactions

-Should not be taken in the presence of:
>Drug allergy
>Liver dysfunction
>Possible liver failure
>G6PD deficiency
-Dangerous interactions may occur if taken with alcohol or also other drugs that are hepatotoxic

Acetaminophen: Toxicity and Managing Overdose

-Even though available over the counter, 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
-Finally Recommended antidote: acetylcysteine regimen

A patient with a history of heavy alcohol use needs a medication for pain. The recommended maximum daily dose of acetaminophen for this patient would be

a.1000 mg.
b.2000 mg.
c.3000 mg.
d.4000 mg.
Rationale: Chronic heavy alcohol abusers may be at increased risk of liver toxicity as a result of excessive acetaminophen use. For this reason, a maximum daily dose of 2000 mg is generally recommended for these persons.

Herbal Products: Feverfew

-Related to the marigold family
-Antiinflammatory properties
-Used to treat migraine headaches, menstrual cramps, inflammation, and also fever
-May cause GI distress, altered taste, therefore muscle stiffness
-May interact with aspirin and other NSAIDs, and also anticoagulants

Nursing Implications

-Before beginning therapy, perform a thorough history regarding allergies and use of other medications, including alcohol, health history, and also medical history
-Obtain baseline vital signs and I&O
-Assess for potential contraindications and drug interactions

Analgesics: Nursing Implications

-Perform a thorough pain assessment, including pain intensity and character, onset, location, description, precipitating and relieving factors, type, remedies, and also other pain treatments
>Pain is now considered a “fifth vital sign”
>Rate pain on a 0 to 10 or similar scale

Nursing Implications

-Be sure to medicate patients before the pain becomes severe so as to provide adequate analgesia and pain control
-Pain management includes pharmacologic and nonpharmacologic approaches therefore be sure to include other interventions as indicated

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 to 12 breaths/min

Opioid Analgesics:
Nursing Implications

-Check dosages carefully
>Follow proper administration guidelines for IM injections, also including site rotation
>Follow proper guidelines for IV administration, including dilution, rate of administration, and so on

Opioid Analgesics:
Nursing Implications

-Constipation is a common adverse effect and
may be prevented with adequate fluid and
fiber intake
-Instruct patients to follow directions for administration carefully and also to keep a record of their pain experience and response to treatments
-Patients should be instructed to change positions but slowly to prevent possible orthostatic hypotension

Opioid Analgesics:
Nursing Implications

-Monitor for adverse effects
>Contact physician immediately if vital signs change, patient’s condition declines, or pain continues
>Respiratory depression may be manifested by respiratory rate of less than 10 breaths/min, dyspnea, diminished breath sounds, or shallow breathing

Opioid Analgesics:
Nursing Implications

-Monitor for therapeutic effects:
>Decreased complaints of pain
>Decreased severity of pain
>Increased periods of comfort
>Improved activities of daily living, appetite, and sense of well-being
>Also Decreased fever (acetaminophen)


Medications that relieve pain without causing loss of consciousness
Opioid analgesics- synthetic drugs that bind to opiate receptors to relieve pain
Adjuvant analgesic drugs- drugs that are added for combined therapy wit a primary drug and may have additive or independent analgesic properties, or both


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


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


injured tissues releases chimicals that propagate pain message
Action potential moves along an afferent fiber to the spinal cord


the pain impulse moves from the spinal cord to the brain

perception of pain

in the brain


neurons from brain stem relaease neurotransmitters that block the pain impulse

pain threshold

Level of stimulus need to produce the perception of pain
A measure of the physiologic 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 physiologic function
Varies by attitude, environment, culture, ethnicity

Classification of Pain by Onset and Duration

Acute pain
Sudden onset
Usually subsides once treated
Chronic pain
Persistent or recurring
Lasts 3 to 6 months
Often difficult to treat


pain that originates from skeletal muscle, ligaments, or joints


pain that originates from organs or smooth muscles


pain that originates from the skin or mucous membranes


pain that occurs in tissues below skin level; opposite of superficial


results from pathology of the vascular or perivascular tissue


pain occurring in an area away from the organ or origin


pain that result from a disturbance of function or pathologic change in a nerve


pain experienced in the area of a body part that has been surgically or traumatically removed


pain resulting from any disorder of causes related to cancer and/or metastasis


pain resulting from any disorder that causes CNS damage

A patient with bone cancer tells the nurse that he is in pain. The nurse knows that bone pain is classified as which type of pain?

a.Somatic pain
b.Referred pain
c.Visceral pain
d.Neuropathic pain*
Rationale: Somatic pain, which includes bone pain, originates from the skeletal muscles, ligaments, and joints. Referred pain occurs when visceral nerve fibers synapse at a level in the spinal cord close to fibers that supply specific subcutaneous tissues in the body. Visceral pain originates from organs and smooth muscles. Neuropathic pain usually results from damage to peripheral or CNS nerve fibers or injury but may also be idiopathic.

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
-gate control theory of pain asserts that non-painful input closes the “gates” to painful input, which prevents pain sensation from traveling to the central nervous system. Therefore, stimulation by non-noxious input is able to suppress pain.

Pain Transmission

Tissue injury causes the release of:
These substances stimulate nerve endings,
starting the pain process

Pain Transmission (cont’d)

-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
-Closing the gate stops the impulses
-If no impulses are transmitted to higher centers in the brain, there is no pain perception

Pain Transmission (cont’d)

-Body has endogenous neurotransmitters:
-Produced by body to fight pain
-Bind to opioid receptors
-Inhibit transmission of pain by closing gate

Pain Transmission (cont’dd)

Rubbing a painful area with massage or liniment stimulates large sensory fibers
-Closes gate
-Reduces pain sensation

Treatment of Pain in Special Situations

-PCA and “PCA by proxy”
PCA by proxy = (activation by someone other than pt)
-Patient comfort vs. fear of drug addiction
-Opioid tolerance
-Use of placebos
-Recognizing patients who are opioid tolerant
-Breakthrough pain
-Synergistic effect

Adjuvant Drugs

-Assist primary drugs in relieving pain
-Example: Adjuvant drugs for neuropathic pain
>amitriptyline (antidepressant)
>gabapentin or pregabalin (anticonvulsants)

Opioid Drugs

-Synthetic drugs that bind to the opiate receptors to relieve pain
-Very strong pain relievers

Opioid Ceiling Effect

-Drug reaches a maximum analgesic effect
-Analgesia does not improve, even with higher doses

Opioid Analgesic 1


Opioid Analgesics 2


Opioid Analgesics 3

codeine sulfate

Opioid Analgesics 4

meperidine HCl (Demerol)

Opioid Analgesics 5

methadone HCl (Dolophine)

Opioid Analgesics 6

morphine sulfate

Opioid Analgesics 7

Hydromorphone (Dilauded)

Opioid Analgesics 8

fentanyl (Duragesic)

Opioid Analgesics 9


Opioid Analgesics:
Mechanism of Action

Three classifications based on their actions:
>Partial agonist


-Bind to an opioid pain receptor in the brain
-Cause an analgesic response (reduction of pain sensation)


-Bind to a pain receptor
-Cause a weaker neurologic response than a full agonist
-Also called partial agonist or mixed agonist


-Reverse the effects of these drugs on pain receptors
-Bind to a pain receptor and exert no response
-Also known as *competitive antagonists

Opioid Receptors and their charicteristics 1

-receptor type: mu
-prototypical agonist: morphine
-effects of opioid stimulation: supranasal analgesia, respiratory depression, euphoria, sedation(moderate level of sedation)

Opioid Receptors and their charicteristics 2

-receptor type: kappa
-prototypical agonist: keocyclazocine
-effects of opioid stimulation: spinal analgesia, sedation (twice as much sedation compared to mu receptors)

Opioid Receptors and their charicteristics 3

-receptor type: delta
-prototypical agonist: enkephalins
-effects of opioid stimulation: analgesia

Opioid Analgesics:

-Main use: to alleviate moderate to severe pain
-Often given with adjuvant analgesic drugs to assist primary drugs with pain relief
-Opioids are also used for:
>Cough center suppression
>Treatment of diarrhea
>Balanced anesthesia

Opioid Analgesics:

-Known drug allergy
-Severe asthma
-Use with extreme caution in patients with:
>Respiratory insufficiency
>Elevated intracranial pressure
>Morbid obesity and/or sleep apnea
>Paralytic ileus

A patient is recovering from an appendectomy. She also has asthma and allergies to shellfish and iodine. To manage her postoperative pain, the physician has prescribed patient-controlled analgesia (PCA) with hydromorphone (Dilaudid). Which vital sign is of greatest concern?

b.Blood pressure
d.Respirations (bc this drugs is a respitory despessant and pt has history of asthma)

Opioid Analgesics:
Adverse Effects

-CNS depression
>Leads to respiratory depression
>Most serious adverse effect
-Nausea and vomiting
-Urinary retention
-Diaphoresis and flushing
-Pupil constriction (miosis)

Opioids: Opioid Tolerance

-A common physiologic result of chronic opioid treatment
-Result: larger dose is required to maintain the same level of analgesia

Opioids: Physical Dependence

-Physiologic 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 psychologic dependence (addiction)