To understand pain relief medication, first you should understand pain...



What is pain??

  • An unpleasant sensory and emotional experience associated with actual or potential tissue damage.

  • Pain results from the stimulation of sensory nerve fibers known as nociceptors that transmit pain signals from various body regions to the spinal cord or brain.

  • Involves physical, psychological, and cultural factors

  • Personal and Individual Experience




  • Pain Threshold: The level of stimulus needed to produce a painful sensation


  • Three main receptors involved with pain: mu, kappa, and delta located in both the CNS and various body tissues

  • Mu receptors influence pain perception

    • High number of mu receptors indicated diminished pain sensitivity

    • With reduced or missing receptors minor noxious stimuli may be perceived as painful

  • Pain Tolerance: amount of pain a person can endure without it interfering with normal function.

    • Pain tolerance can vary from person to person or even within the same person depending on the circumstances involved.

Emotional response to pain is influenced by the patient's age, sex, culture, previous pain experience, and anxiety level.

Pain Threshold



Anger, anxiety, depression, discomfort, fear, isolation, chronic pain, sleeplessness, tiredness


Diversion, empathy, rest, sympathy, medication

MYTBUSTERS: Who has more pain tolerance (not threshold)- males or females??

**While the pain threshold is generally the same for every individual, the pain tolerance varied. Results could be affected by factors such as anger/anxiety that lowered the threshold or medication or rest that raised it.


  • Acute Pain: sudden and usually subsides when treated (i.e. postoperative pain)

  • Chronic Pain: persistent or recurring, lasting 3 to 6 months

    • Often more difficult to treat because of increased tolerance or physical dependence.

Type of Pain





Sudden (minutes to hours); usually sharp, localized; physiologic response (SNS: tachycardia, sweating, pallor, increased blood pressure)

Limited (has an end)

Myocardial infarction, appendicitis, dental procedures, kidney stones, surgical procedures


Slow (days to months); long duration; dull, persistent aching

Persistent or recurring (endless)

Arthritis, cancer, lower back pain, peripheral neuropathy



Somatic Pain: originates in skeletal muscles, ligaments, and joints

Visceral Pain: originates from organs and smooth muscles

Superficial Pain: originates from the skin and mucous membranes

Deep Pain:occurs in tissues below the skin level


Vascular Pain: originate from the pathology of the vascular or perivascular tissues and is thought to account for a large percentage of migraine headaches

Referred Pain: occurs when visceral nerve fibers or synapse at a level in the spinal cord close to fibers that supply specific subcutaneous tissues in the body

Neuropathic Pain: results from damage to peripheral or CNS nerve fibers by disease or injury but may also be idiopathic (unexplained)

Phantom Pain: occurs in the area of a body part that has been removed-surgically or traumatically-and is often described as burning, itching, tingling, or stabbing

Cancer Pain: results from mechanical pressure of tumor mass against nerves, organs, or tissues, Other causes include hypoxia from blockage of blood supply to an organ, metastases, pathologic features, muscle spasms, and adverse effects of radiation, surgery, and chemotherapy

Central Pain: occurs with tumors, trauma, inflammation, or disease affecting CNS tissues


  • Most common

  • Uses the analogy of the gate to describe how impulses from damaged tissues are sensed in the brain

  • STEP 1

    • Tissue injury causes the release of substances bradykinin, histamine, postassium, prostaglandins, serotonin

  • STEP 2

    • Action potential is initiated

    • Travels along a sensory nerve fiber

    • Activates a pain receptor

  • STEP 3

    • Pain fibers enter the spinal cord in the doral horn

      • "Gates" are located in the dorsal horn

    • Pain impulses travel to the brain

  • The gates regulate the flow of sensory impulses to the brain

  • If the impulse is blocked at the gate, it never reaches the brain and no pain is perceived


What is an analgesic?

  • a medication that relieve pain without causing loss of consciousness (sometimes referred to as painkillers)


Opioid Analgesics

  • originate from opium poppy plan
  • only 3 alkaloids clinically usefull : morphine, codeine, and papaverine
    • morphine and codeine are pain relievers
    • papverine is a smooth muscle relaxant
  • 3 different chemical classes of opiod
    • morphine - like drugs
    • meperidine - like drugs
    • methadone - like drugs
  • for severe pain
  • for severe and chronic pain
  • second most commonly used opiod
    • rapid onset of action and a short duration
    • comes in a transdermal patch (chronic pain)
    • lollipop form (newest) for cancer pain management
    • caution with IV for, if given to fast can cause chest wall rigidity
Meperidine (demerol)
  • high abuse and high addiction rates
  • short term use, usually less than 72 hours
    • normeperidine - active metabolite that can accumulate to toxic levles leading to seizures

Indications of us for opiod analgesics
  • mainly to alleviate moderate to severe pain
  • often given additionally with
    • NSAIDS
    • Antidepressents
    • Anticonvulsants
    • Corticosteroids
  • when given with adjucant analgesic agents side effects are decreased and a synergist effect occurs (1+1=3)
  • also used for cough suppression
  • diarrhea
  • balanced anesthesia
Side Effects
  • Respiratory depression *MOST SERIOUS*
  • Euphoria
  • CNS depression
  • N & V
  • Urinary retention
  • Diaphoresis and flushing
  • pupil constrictionconstipation
  • itching
  • known drug allergy
  • severe asthma or other respiratory insufficiency
  • elevated ICP
  • Caution with pregnancy
Nursing Implications
  • Take health history, allergies, meds, alcohol use
  • baseline I&O and VS
  • asses possible contraindications
  • before begining therapy
    • perform pain assesment
    • medicate pt before pain becomes severe
    • use pharmacological and nonpharmacological approaches
    • notify MD with signs of allergic reaction or adverse effects

Opiate Antagonists

Naloxone (Narcan)
  • reversal of respiratory depression
  • last about 1 hour and may reappear for long acting opiods.
Naltrexone (Revia)
  • Used for complete or partial reversal of opiod-induced respiratory depression
  • reverses pain control

Opioid Tolerance
  • physiologic result from chronic opiod use
    • meaning larger does are needed to have therapeutic effect
physical dependence
  • physiologic adaptation of the body to presence of opioid
    • if drug stopped abruptly withdraw symptoms occur
      • narcotic withdrawl
      • opioid abstinence syndrome
        • manifested as: anxiety, irritability, chills, hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, NVD, abdominal crampsshould not be confused with addiction
        • misunderstanding leads to ineffective pain management and contribute to under treatment of pain"break - through" pain
    • get shorter or fast acting forms on a regular schedule
    • baseline dose of the narcotic may need to be titrated up, or increased in increments
Nursing Implications
  • Notify MD and withhold med if
    • decline in pt overall condition
    • vs are abnormal
      • bad if respiratory rate is less than 12 breaths/min
  • check dosage carefully!
  • ensure safety measures
  • constipation prevented with adequate fluid and fiver intake
  • encourage pt to keep record of pain experience and response to treatment
  • possible orthostatic hypotension
  • PO forms take with food

NONopioid Analgesics

  • analgesic and antipyretic effects
  • little to no antiinflammatory effects
  • available OTC and can be found in combination products with opioids
  • mild to moderate pain
  • fever
  • alternative for pts who can't take asprin
  • Toxicity and Overdose
    • lethal when overdosed
      • causes hepatic necrosis
      • nephropathy
      • recommended antidote: acetylcysteine
    • managmenet
      • max adult dose 4000mg/ day
      • inadvertent excessive doses may occur when different combo drug products are taken together
      • no acetaminophen content in all current meds pt is taking
      • antidote Acetylcysteine (Mucomyst)
        • foul smelling and can only be given for single ingestions
  • Interactions
    • dangerous interactions can occur when taken with alcohol
    • should not take if have:
      • liver dysfunction
      • possible liver failure
      • when taking other hepatotoxic drugs

Monitor for Therapeutic Effects

* decreased pain complaints

* decreased pain severity

* increased comfort

* improved ADLs, appetite, and sense of well-being

* decreased fever with acetaminophen

Name of Drug
Mechanism of Action
Side Effects
Adverse Effects
Patient Education
Opiate Agonist
morphine sulfate
Severe Pain
· Bind to an opioid pain receptor in the brain
· Cause an analgesic response (reduction of pain sensation)
-Respiratory Depression
-CNS depression
-Nausea and vomiting
-Urinary retention
-Diaphoresis and flushing
-Pupil constriction
Withhold dose if respirations < 12/min
Severe asthma or other respiratory insufficiency
Elevated intracranial pressure
Use with caution in pregnancy
Opiate Agonist
codeine sulfate
· Moderate Pain
· Cough Suppressant
Same as above
Same as above
Same as above
Opiate Agonist
meperidine HCl (Demerol)
· Postoperative pain
· Severe Pain in the ER
· Short-term pain management
<72 hours
Same as above
Same as above
Normeperidine – an active metabolite
Can accumulate to toxic levels and lead to seizures
Same as above
· High Abuse
· High Addiction
Opiate Agonist
methadone HCl (Dolophine)
· Opiod Abstinence Syndrome
· Addictions (Heroin)
Same as above
-Does not produce the euphoric effect of other opiate Agonists
Same as above with the exception of euphoric effect
Use with caution in pregnancy/breastfeeding
Opiate Agonist
Oxycodone CR (OxyContin)
Severe Pain
Chronic Pain
· Binds to an opioid pain receptor in the brain
· Causes reduction of pain sensation
Same as above
Severe asthma or other respiratory insufficiency
Elevated intracranial pressure
Use with caution in pregnancy
Opiate Agonist
Moderate – Severe Pain
Cough Suppressant
Same as above
Same as above
Same as above
Opiate Agonist
Fentanyl citrate
Severe Pain
Chronic Pain
Same as above
Rapid Onset – Short Duration
Same as above and:
IV SLOW PUSH – pushing quickly can cause chest wall rigidity
Same as above
· Available in Patch for chronic pain management
· Available in lollipop form – Cancer Patients
Opiate Antagonist
naloxone (Narcan)
Reversal for narcotic drugs
Bind to opiate receptors and prevents a response
Used for complete or partial reversal of
opioid-induced respiratory depression
Reverses the respiratory depression but also reverses the pain control!
Respiratory depression may reappear for long-acting opioids!


~Drugs that depress the CNS

Types of Anesthetics

1) General anesthesia- create a state in which the CNS is altered, indications include surgical procdures and electroconclusive therapy

  • Purpose: pain relief/sensory loss, depression of conciousness, skeletal muscle relaxation, reflex reduction, smooth muscle relaxation, and paralysis of respiratory muscles (may be require one or more drug to produce all)
  • Types: Inhaled- volitale liquids or gases that are vaporized in oxygen (eg. halothane, isoflurane, enflurane, methoxyflurane, nitrous oxide)

Injectable-IV administered, used to create/maintain anethesia, produce amnesia, use in addition to inhaled
(eg. propofol/diprivan, ketamine/ketalar)
*Diprivan= rapid onset (30-60 seconds), rapid recovery (10-25 minutes), less hangover effects
*Ketalar=rapid onset (30 seconds), longer recovery (45 minutes), used when cardiac depression is not safe

  • Side Effects/Adverse Effects: diprivan may cause local burning at injection site, bradycardia, hypotesion, pulmonary edema
  • Side Effects/Adverse Effects: ketalar is able to cross the blood-brain barrier and cause hallucinations, dreams, psychotic episodes
  • More Side/Adverse Effects: dependent on dose and drug used- heart complications, peripheral circulation, liver and kidney complications, respiratory tract, and myocardial depression
  • Contrainications: allergy, pregnancy, narrow angle glaucoma, known history of malignant hyperthermia

Malignant hyperthermia- not common, potentially fatal, typically genetic, produces an adverse metabolic reaction to GA. Ususally occurs with inhaled anesthetics or depolarizing NMBD (succinylcholine)
S/S: tachycardia, tachypnea, muscle rigidity, rise in body temp greater than 104= LIFE THREATENING
Treatment: support heart and lungs, give Dantrolene to reduce muscle rigidity

2) Balanced Anethesia: also called combination, and allows less of each drug to be used, less side effects, and is a more controlled state

  • Involves a sedative (barbituates such as thiopental/pentothal), benzodiazepines (midazolam/versed), opiod (narcotics like morphine or fentanyl)
  • Also use anticholinergics (atropine), NMBA's (succinylcholine), nondepolarizing agents (vecuronium)

Side Effects-depression of CNS, bradycardia, hypotension, supressed respirations, decreased GI motility, nausea and vomitting post op

-Breakdown of the Drugs

~Thiopental (Pentothal): IV med used for rapid anethesia, it can be maintained by inhaled drug. It has a rapid onset of 10-30 seconds and recovery time of 5-8 minutes
it is lipophilic and absorbed fast through the blood-brain barrier

~Midazolam (Versed): potent and used to induce amnesia and be continuous sedation for intubaded patients. Used for diagnostic, endoscopic, and therapeutic procedures
Function not known, but also has a rapid onset and peak of 30 to 60 minutes. Side effects include drowsiness, sedations, constipation, disorientation

Neuromuscular Blocking Agents
~Succinylcholine, Vercuronium: these prevent nerve transmission in certain muscles which produces paralysis, is used in conjunction with anethetics. Requires a vent,
and do not relieve pain or provide sedation. Used to maintain controlled vent, reduce muscle contractions in area of surgery, and diagnostic
for myasthenia gravis. Side effects include hypotension, tachycardia. Overdose could cause cardiac collapseand/or need ventilation.

3) Local Anesthetics

  • Used for surgical, dental, and diagnostic procedures as well as certain types of pain.

  • Can be topical (skin, mucus membranes) or parenteral (spinal injections)
  • Respiratory muscles not paralyzed, and does get rid of pain
  • Types: intrathecal, epidural, infiltration, nerve block, topical

-Breakdown of the Drugs

~Lidocaine (Xylocaine) is a local that is short acting, and dangerous if systemically absorbed
~Ropivacaine (Naropin) epidural/spinal, good pain management for obstetrics/post op, avoid rapid infusion
~Mepivacaine (Carbocaine)
~Procaine (Novocain)
~Tetracaine (Pontocaine)
~Bupivaine (Marcaine)

  • When used on you: autonomic, then pain/sensory functions, and then motor activity is lost. When recovering it wears off in reverse order.
  • Side effects are small but can result in accidentally IV injection, too much of a dose, slow metabolic breakdown, could be injected into highely vascular tissue

4) Moderate/Concious Sedation

  • No ventilation required, patient can respond to verbal commands, used for diagnostic and minor procedures, can be combined with local ansthetics
  • fast recovery and better safety profile than general anesthesia
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-Breaking Down the Drugs

~Midazalam (Versed): IV benzo
~Morphine/Fentanyl: opiate analgesic
-these meds reduce anxiety and sensitivity to pain and patinet won't remember it afterwards

Nursing Implications

  1. Assess alcohol and drug use
  2. Obtain baseline VS, lab work, EKG, ABC's
  3. Continually monitor all body systems
  4. Be wary of cardiac or respiratory depression post op
  5. Make patient aware of awake feeling with NMBA's
  6. Teach deep breathe and cough for post op

Inhaled Anesthetics
- Isoflurane
-Nitrous oxide
-To induce or maintain general anesthesia
Sites primarily affected:
-Peripheral circulation
- Liver
-Respiratory tract
-Myocardial depression
-Drug allergy
-Pregnancy – depending on drug type
-Narrow angle glaucoma
-Known susceptibility: Malignant Hyperthermia
Injectable Anesthetics
-Ketamine (Ketalar)
-To induce or maintain general anesthesia
-As an adjunct to inhalation-type anesthetics
Propofol (Diprivan)
-Local burning at injection site
-Bradycardia, hypotension, pulmonary edema
Ketamine (Ketalar)
Crosses blood brain barrier:
-hallucinations, dreams, psychotic episodes
Propofol (Diprivan)
-Rapid onset: 30-60 sec
-Recovery: 10-25 min
-Less “hangover” effect
Ketamine (Ketalar)
-Rapid Onset: 30 Seconds
-Recovery: 45 minutes
-Useful in situations where cardiac depression is dangerous
Balanced Anesthesia
-Thiopental (Pentothal)
-IV Drug used to induce rapid anesthesia
Associated with depression of the CNS:
Decreased pulse
Suppressed respirations
Decreased GI activity
Nausea and vomiting after recovery
Thiopental (Pentothal)
Very rapid onset of action:
10 – 30 seconds
Very short recovery time:
5-8 minutes
Balanced Anesthesia
-Midazolam (Versed)
Produces sedation and amnesia for:
-Diagnostic, Endoscopic, Therapeutic Procedures
-Drowsiness, sedation, constipation, phlebitis at IV site, disorientation
Midazolam (Versed)
-Rapid Onset – Peak effectiveness 30-60 min
-Patients can follow commands
-Patients have no memory of procedure
Balanced anesthesia
Same as above
See Anticholinergics
See Anticholinergics
Balanced Anesthesia
· Maintaining controlled ventilation during surgery
· Endotracheal intubation
· To reduce muscle contractions during surgery
· Diagnostic agents for myasthenia gravis
paralysis requiring prolonged mechanical ventilation
Cardiovascular collapse
Conditions that increase sensitivity include:
Electrolyte imbalances
Myasthenia gravis
Balanced Anesthesia
- Fentanyl
Adjunct to inhaled or injectable anesthetics
See Chapter 10 Study Guide
See Chapter 10 study guide
Local Anesthesia
-Ropivacaine (Naropin)
Adverse effects result if:
· Intravascular injection occurs
· Excessive dose or rate of injection n
· Slow metabolic breakdown
· Injection into a highly vascular tissue
Avoid rapid infusion
Good pain relief for Obstetrics and Postoperatively
Local Anesthesia
Bupivacaine (Marcaine)
Same as above
Local Anesthesia
Lidocaine (Xylocaine)
Same as above
Short acting – preferred for short procedures
Danger of absorbed systemically
Moderate Sedation
Conscious Sedation
Midazalam (Versed)
Morphine or Fentanyl
GI procedures, endoscopy
Rapid recovery time and greater safety profile than general anesthesia
See above for Midazalam (versed)
See chapter 10 for Morphine/Fentanyl
Anxiety and sensitivity to pain are reduced, and patient cannot recall the procedure

All References

Lane, L, Collins, S, Harington, S, Rainforth, S, & S., J. (2010). Pharmacology and the nursing process.Mosby Inc.

Petges, Nancy RN MSN. Pharmacology : Analgesic Agents Powerpoint, 2011.