CHAPTER 18
DRUGS FOR THE CONTROL OF PAIN
LEARNING OUTCOME 1
Relate the importance of pain assessment to effective pharmacotherapy.
Concepts
1. Pain is a subjective experience in that patients may describe the same degree and type of pain differently.
Health care workers are assisted in the assessment of pain with the use of numerical scales and survey
instruments. Effective pharmacotherapy pain management is depen dent on accurate assessment of the
degree of pain and on determining underlying disorders that may be causing the pain.
2. Pain may be classified as either acute or chronic. Acute pain is usually an intense pain lasting for a defined
period of time, whereas chronic pain lasts longer than six months and may interfere with daily activities.
3. Sources of pain are classified as nociceptor pain, which is due to injury to tissues, and neuropathic pain,
which is caused by injury to nerves. Nociceptor pain is usually exhibited as sharp, localized pain or dull,
throbbing, aching pain. Burning, shooting, or numbing pain characterizes neuropathic pain.
LEARNING OUTCOME 2
Explain the neural mechanisms at the level of the spinal cord responsible for pain.
Concepts
Pain transmission begins when nociceptors are stimulated. Nociceptors are pain receptors found throughout the
body. The spinal cord receives the pain impulse along two types of sensory neurons, the A ≠ fibers, which are
wrapped in myelin, and the C fibers, which are unmyelinated. A ≠ fibers signal sharp, well-defined pain, and C
fibers signal dull, poorly localized pain. Since pain signals begin at the level of nociceptors in peripheral tissues
and travel through the CNS, there are several target areas for pharmacological and nonpharmacological
interruption of the pain transmission. Pain interruption may act at the peripheral level or at the CNS level.
LEARNING OUTCOME 3
Explain how pain can be controlled by inhibiting the release of spinal neurotransmitters.
Concepts
Neurotransmitters are responsible for passing the message of pain on to neurons once the pain impulse reaches
the spinal cord. The neurotransmitter called substance P is responsible for continuing the pain message to the
brain and can be affected by other neurons released from the CNS. Examples of the neurons that can affect
substance P are endogenous opioids, which include endorphins, dynorphins, and enkaphalins. Endogenous
opioids may modify sensory information at the level of the spinal cord, interrupting the transmission of pain.
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Ch 18-1
LEARNING OUTCOME 4
Describe the role of nonpharmacologic therapies in pain management.
Concepts
1. Due to the side effects of medications for pain, some patients choose nonpharmacological pain management
over pharmacological management. These therapies may be used in place or as an adjunct to medications. If
used as an adjunct, lower doses of pain medications are needed. Nonpharmacological therapies include
acupuncture, massage, heat or cold, relaxation, chiropractic manipulation, and transcutaneous electrical
nerve stimulation (TENS).
2. Patients with intractable cancer pain may require more invasive therapy, such as radiation or chemotherapy,
to reduce tumor size; relieving nerve stimulation; or surgery to remove the tumor completely. Nerve blocks
are also used on patients with intractable pain.
LEARNING OUTCOME 5
Compare and contrast the types of opioid receptors and their importance in effective management of pain.
Concepts
Opioid medications interact with opioid receptors to control pain. Opioid agonists are drugs that stimulate
certain receptors, and opioid antagonists block certain receptors. The opioid receptors include mu, kappa,
sigma, delta, and epsilon. Examples of the pharmacology involved includes morphine, which activates mu and
kappa receptors; pentazocine (Talwin), which is a mixed agonist–antagonist since it activates the kappa receptor
but blocks the mu receptor; and naloxone (Narcan), which inhibits both the kappa and mu receptors.
Table 18.1 Responses Produced by Activation of Specific Opioid Receptors
LEARNING OUTCOME 6
Explain the role of opioid antagonists in the diagnosis and treatment of acute opioid toxicity.
Concepts
Acute opioid toxicity causes severe respiratory depression and is a medical emergency. Naloxone (Narcan) is an
opioid antagonist that inhibits mu and kappa; therefore, it is used to reverse respiratory depression and other
symptoms of opioid toxicity. If the patient is unconscious from apparent opioid toxicity and information is not
available as to the drug that has been taken, opioid antagonists aid in diagnosing the overdose. If the patient’s
symptoms do not reverse rapidly, the overdose was most likely not due to an opioid substance.
Prototype Drug

morphine (Astrmorph PF, Duramorph, others)

naloxone (Narcan)
Table 18.2 Opioids for Pain Management
Table 18.3 Nonopioid Analgesics
Ch 18-2
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LEARNING OUTCOME 7
Describe the long-term treatment of opioid dependence.
Concepts
1. Although effective at relieving pain, the opioids have a greater risk for dependence than almost any other
class of medications; tolerance develops relatively quickly. One common method of treating opioid
dependence is to switch the patient from IV and inhalation forms of illegal drugs to methadone (Dolophine).
Although an opioid, oral methadone does not cause the euphoria of injectable opioids. Methadone does not
cure the dependence; however, the patient must continue taking the drug to avoid withdrawal symptoms.
This therapy, called methadone maintenance, may continue for many months or years, until the patient
decides to enter a total withdrawal treatment program.
2. A newer treatment option is to administer buprenorphine (Subutex), a mixed opioid agonist–antagonist, by
the sublingual route. This drug is used early in opioid abuse therapy to prevent opioid-withdrawal
symptoms. Suboxone, a combination agent, is used later in the maintenance of opioid addiction.
LEARNING OUTCOME 8
Compare the pharmacotherapeutic approaches of preventing migraines to those of aborting migraines.
Concepts
1. There are two primary goals for the pharmacological therapy of migraines (see Table 18.4). The first is to
stop migraines in progress, and the second is to prevent migraines from occurring. The drugs used to abort
migraines are different from those used for prophylaxis. Drug therapy is most effective if begun before a
migraine has reached severe level.
2. There are two major drug classes that stop migraines in progress: triptans and ergot alkaloids. Both
stimulate serotonin (5-HT).
3. Triptans, such as sumatriptan (Imitrex), are selective for 5-HT receptor subtype and act by constricting
certain blood vessels in the brain.
4. Ergot alkaloids, such as ergotamine (Ergostat), interact with adre nergic, dopaminergic, and serotonin
receptors and promote vasoconstriction, which stops ongoing migraines.
5. Drugs for migraine prophylaxis include beta-adrenergic blockers, calcium channel blockers, antidepressants,
and antiseizure drugs. These drugs are started when the number of migraines is high and the patient does not
respond to the drugs used to stop migraines.
Table 18.4 Antimigraine Drugs
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Ch 18-3
LEARNING OUTCOME 9
Describe the nurse’s role in the pharmacologic management of patients receiving analgesics and antimigraine
drugs.
Concepts
1. The role of the nurse in opioid therapy involves careful monitoring of a patient’s condition and providing
education as it relates to the prescribed drug treatment. Perform an initial assessment to determine the
presence or history of severe respiratory disorders, ICP, seizures, and liver or renal disease. Obtain an
allergy history before administering these drugs. Complete lab work as ordered by the physician. Assess the
patient’s pain level before and during therapy, including the character, duration, location, and intensity of
pain. Obtain a history of current medication, especially alcohol and other CNS depressants. Assess the
social context of the patient’s environment for the potential for opioid dependency. If giving to drugdependent patient, monitor for signs of opioid withdrawal such as cramping, vomiting, hypertension, and
anxiety. Opioids should not be administered if respirations are below 12 per minute, and narcotic
antagonists such as Narcan should be readily available to reverse the effects. Assistance with activity is
important. Monitor urine output for retention and patient’s bowel habits for constipation.
2. With the use of opioid antagonist therapy, the nurse wants to continue the careful monitoring of the patient’s
condition, especially the respiratory status. Have resuscitative equipment available.
3. In the care of the patient using nonopioid analgesics, careful monitoring of a patient’s condition and
providing education as it relates to the prescribed drug treatment is necessary. If the patient is on high doses
of these medications, complete a thorough assessment for the presence or history of hypersensitivity,
bleeding disorders, gastric ulcers, severe renal or hepatic disease, and pregnancy. Obtain laboratory tests on
the patient’s renal and liver function as ordered by the physician during the patient’s pharmacotherapy.
Good pain assessment is needed, including location, character, and intensity of pain. Monitor patient for
side effects.
4. Migraine therapy also involves monitoring the patient’s condition and providing education regarding the
medication regimen. Data collection will include the frequency and intensity of the migraine headaches and
the presence or history of MI, angina, and hypertension and the presence or history of renal and liver
disease, diabetes, and pregnancy. Assess vital signs and the patient’s stress levels and coping mechanisms,
because migraines may be associated with these factors. Assess the patient’s neurological status. Provide a
quiet, calm environment with decreased noised and lighting. Apply cold packs to help lessen the pain.
Assess the pain level before medication administration. Monitor for side effects: dizziness, drowsiness,
tingling, weakness, and GI complaints.
Prototype Drug

Ch 18-4
sumatriptan (Imitrex)
Adams_IRM
LEARNING OUTCOME 10
For each of the drug classes listed in Drugs at a Glance, know representative drug examples, and explain the
mechanisms of drug action, primary actions, and important adverse effects.
Concepts
1. Opioid (narcotic) analgesic: Prototype drug: opioid agonists (morphine). The mechanism of action is to
exert the effects by interacting with specific receptors. The primary use is for moderate to severe pain that
cannot be controlled with other classes of analgesics and as anesthesia. Adverse effects can include
respiratory depression, sedation, nausea, and vomiting. Opioids with mixed agonist–antagonist activity:
(example: Talwin) stimulate the opioid receptor; thus, they cause analgesia. However, the withdrawal
symptoms or side effects are not as intense.
2. Opioid antagonists: Prototype drug: naloxone (Narcan). The mechanism of action is to interact with at least
six types of receptors. The primary use may be to reverse the respiratory depression and other acute symptoms.
Adverse effects may include overdose as a result of overly aggressive pain therapy or as a result of substance
abuse. This is a medical emergency, with respiratory depression being the most serious problem.
3. Nonopioid analgesics: Prototype drug: acetaminophen (Tylenol). The mechanism of action to treat fever is
at the level of the hypothalamus and causes dilation of peripheral blood vessels enabling sweating and
dissipation of heat. The primary use is for the treatment of fever and to relieve pain. Adverse effects are
uncommon with therapeutic doses. Nonsteroidal anti-inflammatory drugs (NSAIDs): Prototype drug:
ibuprofen (Motrin). The mechanism of action is to inhibit cyclooxygenase, an enzyme responsible for the
formation of pro staglandins. With the enzyme inhibited, inflammation and pain are reduced. Primary use is
for mild or moderate pain, especially for pain associated with inflammation. Adverse effects may include GI
upset, such as gastric ulcers and bleeding and acute renal failure. Salicylates: Prototype drug: aspirin
(ASA). The mechanism of action has anticoagulant, antipyretic, anti-inflammatory, and analgesic abilities.
The adverse effects are possible GI distress and bleeding in high doses. Aspirin may increase the action of
oral hypoglycemic agents. Selective Cox-2 inhibitors: Prototype drug: celecoxib (Celebrex). The
mechanism of action is similar to the NSAIDs. The primary use is for relief of pain, fever, and
inflammation. Adverse effects are mild and related to the GI system. Centrally acting agents: Prototype
drug: tramadol (Ultram). The mechanism of action is weak opioid activity. The primary use is as centrally
acting analgesics. Adverse effects can include: CNS, GI, CV, and dermatologic effects.
4. Antimigraine agents: Two drug classes—(1) the Tripans: Prototype drug: sumatriptan (Imitrex) and (2)
ergot alkaloids. The mechanism of action for both is to act as serotonin agonists. The Tripans are thought to
act by constricting certain intracranial vessels. The primary use is to abort migraines with or without auras.
Adverse effect is GI upset. The mechanism of action of the ergot alkaloids is to promote vasoconstriction.
The primary use is to terminate ongoing migraines. Adverse effects can include nausea, vomiting, weakness
in the legs, myalgia, numbness and tingling in fingers and toes, angina-like pain, and tachycardia.
Prototype Drug

naloxone (Narcan)

aspirin (Acetylsalicylic Acid, ASA)
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Ch 18-5
LEARNING OUTCOME 11
Categorize drugs used in the treatment of pain based on their classification and mechanism of action.
Concepts
1. Opioid (narcotic) analgesic: Opioid analgesic medications exert their effects by interacting with specific
receptors. Opioids are the drugs of choice for moderate to severe pain that cannot be controlled with other
classes of analgesics. Some opioids are used for anesthesia. Examples: Hydrocodone, OxyContin, Percocet.
2. Opioids antagonists: Overdose can occur as a result of overly aggressive pain therapy or as a result of
substance abuse. This is a medical emergency, with respiratory depression being the most serious problem.
The opioid antagonists may be used to reverse the respiratory depression and other acute symptoms.
Examples: Revex, Narcan, Trexan.
3. Nonopioid analgesics: ASA is used for the treatment of fever and to relieve pain. Nonsteroidal antiinflammatory drugs (NSAIDs) inhibit cyclooxygenase, an enzyme responsible for the formation of
prostaglandins. With the enzyme inhibited, inflammation and pain are reduced. Use for mild or moderate
pain, especially for pain associated with inflammation. Salicylates have anticoagulant, antipyretic, antiinflammatory, and analgesic abilities. Selective Cox-2 inhibitors relieve pain, fever, and inflammation and
are similar to other NSAIDs. Centrally acting agents that have weak opioid activity. Examples: Cataflam,
Dolobid, Lodine, Nalfon.
4. Antimigraine agents: two drug classes—(1) the Tripans and (2) ergot alkaloids. Mechanism of action:
They are both serotonin agonists. The Tripans are thought to act by constricting certain intracranial vessels.
The ergot alkaloids promote vasoconstriction, which terminates ongoing migraines. Examples: Migranal,
Axert, Relpax, Frova.
.
LEARNING OUTCOME 12
Use the nursing process to care for patients receiving drug therapy for pain.
Concepts
1. Assessment of a patient on drug therapy for pain would include careful monitoring of a patient’s condition.
Assess vital signs, particularly respiratory status. Assess the patient’s pain level before and during therapy
including the character, duration, location, and intensity of pain. Obtain a history of current medication,
especially alcohol and other CNS depressants. Assess for the presence or history of hypersensitivity,
bleeding disorders, gastric ulcers, severe renal or hepatic disease, and pregnancy. Obtain history of the
frequency and intensity of the migraine headaches. Assess the patient’s stress levels and coping
mechanisms, as migraines may be associated with these factors. Monitor for side effects and the potential
for dependency.
2. Nursing diagnoses: Knowledge Deficit regarding condition, Therapeutic Regimen, and Potential Side Effects
of Medication; Risk for Dependency related to opioid therapy.
3. Planning: The goal for patients receiving medication for pain control is to explain the proper use of
medication and to be free of pain without dependency.
4. Implementation: Encourage compliance with medication regimen. Provide additional education regarding
medication regimen, such as consultation with the clinical pharmacist, written and/or visual edu cational
material, and home-health visits to ensure patient’s ability to follow prescribed therapy.
Ch 18-6
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5. Evaluation: An ideal outcome criterion for evaluation of the plan of care is pain control with limited side
effects and no dependency. Patient is able to verbalize the importance of taking prescribed medications to
assist in continued management of the disease.
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Ch 18-7