Chapter 10 Analgesic Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Chapter 10

Analgesic Drugs

Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

Medications that relieve pain without causing loss of consciousness

“Painkillers” Opioid analgesics Adjuvant analgesic drugs

Analgesics

Copyright © 2014 by Mosby, an imprint of Elsevier Inc. 2

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


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

Nociception


Nociception (cont’d)


Level of stimulus needed to produce the perception of pain

A measure of the physiologic response of the nervous system

Pain Threshold


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

Pain Tolerance


Acute pain Sudden onset Usually subsides once treated

Chronic pain Persistent or recurring Lasts 3 to 6 months Often difficult to treat

Classification of Pain by Onset and Duration


Classification of Pain

Somatic Visceral Superficial Deep Vascular

Referred Neuropathic Phantom Cancer Central


Classroom Response Question

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


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 Theory of Pain Transmission



Gate Theory of Pain Transmission (cont’d)

Tissue injury causes the release of: Bradykinin Histamine Potassium Prostaglandins Serotonin

These substances stimulate nerve endings, starting the pain process

Pain Transmission


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 Transmission (cont’d)


Closing the gate stops the impulses If no impulses are transmitted to higher centers

in the brain, there is no pain perception



Body has endogenous neurotransmitters Enkephalins Endorphins

Produced by body to fight pain Bind to opioid receptors Inhibit transmission of pain by closing gate



Rubbing a painful area with massage or liniment stimulates large sensory fibers

Result Closes gate Reduces pain sensation



PCA and “PCA by proxy” Patient comfort vs. fear of drug addiction Opioid tolerance Use of placebos Recognizing patients who are opioid tolerant Breakthrough pain Synergistic effect

Treatment of Pain in Special Situations


Assist primary drugs in relieving pain NSAIDs Antidepressants Anticonvulsants Corticosteroids

Example: Adjuvant drugs for neuropathic pain amitriptyline (antidepressant) gabapentin or pregabalin (anticonvulsants)

Adjuvant Drugs


Synthetic drugs that bind to the opiate receptors to relieve pain

Very strong pain relievers

Opioid Drugs


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

doses pentazocine nalbuphine

Opioid Ceiling Effect


codeine sulfate meperidine HCl (Demerol) methadone HCl (Dolophine) morphine sulfate hydromorphone fentanyl (Duragesic) oxycodone Others

Opioid Analgesics (cont’d)


Three classifications based on their actions: Agonist Partial agonist Antagonist

Opioid Analgesics:Mechanism of Action


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

sensation)

Agonists


Bind to a pain receptor Cause a weaker neurologic response than a full

agonist Also called partial agonist or mixed agonist

Agonists-Antagonists


Reverse the effects of these drugs on pain receptors

Bind to a pain receptor and exert no response Also known as competitive antagonists

Antagonists


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:Indications


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 Pregnancy

Opioid Analgesics: Contraindications



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?

A. Pulse

B. Blood pressure

C. Temperature

D. Respirations


CNS depression Leads to respiratory depression Most serious adverse effect

Nausea and vomiting Urinary retention Diaphoresis and flushing Pupil constriction (miosis) Constipation Itching

Opioid Analgesics: Adverse Effects


A common physiologic result of chronic opioid treatment

Result: larger dose is required to maintain the same level of analgesia

Opioids: Opioid Tolerance


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)

Opioids: Physical Dependence


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 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.


naloxone (Narcan) naltrexone (ReVia) Regardless of withdrawal symptoms, when a patient

experiences severe respiratory depression, an opioid antagonist should be given.

Opioid Analgesics: Toxicity and Management of

Overdose


Toxicity and Management of Overdose (cont’d)

Opioid withdrawal/opioid abstinence syndrome Manifested as:

Anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea, confusion


Opioid Analgesics: Interactions

Alcohol Antihistamines Barbiturates Benzodiazepines Monoamine oxidase inhibitors


Analgesic and antipyretic effects Little to no antiinflammatory effects Available over the counter and in combination

products with opioids

Nonopioid Analgesics:Acetaminophen (Tylenol)


Similar to salicylates Blocks pain impulses peripherally by inhibiting

prostaglandin synthesis

Acetaminophen: Mechanism of Action


Mild to moderate pain Fever Alternative for those who cannot take aspirin

products

Acetaminophen: Indications


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

Be aware of the acetaminophen content of all medications taken by the patient (OTC and prescription)

Acetaminophen: Dosage


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 other drugs that are hepatotoxic

Acetaminophen: Contraindications/Interactions


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

Recommended antidote: acetylcysteine regimen

Acetaminophen: Toxicity and Managing Overdose




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.

Related to the marigold family Antiinflammatory properties Used to treat migraine headaches, menstrual cramps,

inflammation, and fever May cause GI distress, altered taste, muscle stiffness May interact with aspirin and other NSAIDs, and

anticoagulants

Herbal Products: Feverfew


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 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 other pain treatments Pain is now considered a “fifth vital sign” Rate pain on a 0 to 10 or similar scale

Analgesics: Nursing Implications (cont’d)


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; be sure to include other interventions as indicated

Analgesics:Nursing Implications (cont’d)


Patients should not take other medications or OTC preparations without checking with their physician

Instruct patients to notify physician for signs of allergic reaction or adverse effects

Analgesics: Nursing Implications (cont’d)


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, including site rotation Follow proper guidelines for IV administration,

including dilution, rate of administration, and so on

Opioid Analgesics: Nursing Implications (cont’d)


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 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 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



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 Decreased fever (acetaminophen)



Chapter 10 Analgesic Drugs Copyright © 2014 by Mosby, an imprint of Elsevier Inc.

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