Drugs Affecting CNS:
OPIOIDS
WHAT IS PAIN?
• Pain is defined as an unpleasant sensation
that can be either acute or chronic and is a
consequences of complex neurochemical
processes in the peripheral and central
nervous system.
Classification of pain
1. Physiological pain – often caused by an injury to body organs
or tissue.
a. Cutaneous pain – skin, surface tissues
b. Somatic pain – ligaments, tendons, bones, and blood vessel
c. Visceral pain – body organs, internal cavities
2. Inflammatory pain – originates from infection or
inflammatory as a result of the initial tissue or organ
damage.
3. Neuropathic pain – is a very complex, chronic pain, resulting
from injury of the nervous system. (burning, shooting, numb
pain)
Acute pain vs Chronic pain
• Acute pain – often severe but usually lasts
only until the removal of the source that
triggered the pain.
- Short duration and lasts less than 3 to 6
months
• Chronic pain – a pain lasting longer than 6
months that persist even when the initial
caused has been resolved through appropriate
medical intervention.
Opioids
• Opioid is a natural or synthetic drug that binds to
opioid receptors producing agonist effects.
• They are well known for their ability to reduce
the perception of pain without a loss of
consciousness.
• An opioid analgesic is a natural or synthetic
morphine-like substance responsible for reducing
moderate to severe pain.
• Opioids are narcotic substances, meaning that
they produce numbness or stupor-like symptoms.
Opioid receptors
3 opioid receptors:
1. Mu receptor
Mu1: located outside spinal cord; responsible for central
interpretation of pain.
Mu2: Located throughout CNS; responsible for respiratory
depression, spinal analgesia, physical dependence, and
euphoria.
2. Kappa receptor
- Found in limb and other diencephalic areas, brain stem, and
spinal cord
- Responsible for spinal analgesia, sedation, dyspnea,
dependence, dysphoria, and respiratory depression.
3. Delta receptor – produces analgesia, dysphoria, delusions,
hallucinations.
Opioid drugs: OPIOID AGONIST
1. Morphine
Receptors: Strong Mu receptor agonist, Kappa receptor agonist
Action:
- Strong Mu receptor agonist, Kappa receptor agonist
- Analgesia: relief of pain without loss of consciousness
- Euphoria: sense of contentment and well-being
- Respiration: Respiratory depression
- Depression of cough reflex: Has antitussive properties
- Miosis: Abusers demonstrate Pinpoint pupils
- Emesis
- GI: Relieves diarrhea by decreasing GI motility
- CV: Hypotension, bradycardia (high doses)
- Hormonal actions: Increase growth hormone release and enhances
prolactin secretion
- Histamine release: urticaria, sweating, vasodilation, bronchoconstriction
- Labor: may prolong the second stage of labor by transiently decreasing the
strength, duration, and frequency of uterine contractions.
Opioid drugs: OPIOID AGONIST
1. Morphine
- Used for severe pain
- It rapidly enters all the body tissues, including the fetuses
of pregnant women.
- Should not be used for analgesia during labor
Adverse effects:
- Hypotension
- Dysphoria (anxiety, depression, or unease)
- Sedation
- Constipation
- Urinary retention
- Nausea
- Potential for addiction
- Respiratory depression
Opioid drugs: OPIOID AGONIST
2. Codeine
- Weak analgesic
- Used for mild to moderate pain
- Commonly used in combination with
acetaminophen for pain management.
- Exhibits good antitussive activity
Opioid drugs: OPIOID AGONIST
3. Oxycodone
Weak analgesic
- Is a semisynthetic derivative of morphine
- Oral analgesic effect is twice that of morphine
4. Oxymorphone
- Is a semisynthetic derivative
- Parenterally it is ten times more potent than
morphine.
- Orally it is three times more potent than
morphine
Opioid drugs: OPIOID AGONIST
5. Hydromorphone
- Semisynthetic analogs of morphine and
codeine
- Orally it is 8 to 10 times more potent
than morphine.
- It is more preferred over morphine in
patients with renal dysfunction due to
less accumulation of active metabolite.
Opioid drugs: OPIOID AGONIST
6. Hydrocodone
- Is a semisynthetic analog of morphine
and codeine
- Weak analgesic than hydromorphone
- Is often combined with acetaminophen
or ibuprofen to treat moderate to severe
pain
Opioid drugs: OPIOID AGONIST
7. Fentanyl
- Is a synthetic opioid
- Has 100-fold the analgesic potency of
morphine and is used for anesthesia
- Administered IV, epidurally, or intrathecally
8. Sulfentanil
- Synthetic opioid agonist related to fentanyl
- More potent than fentanyl
- Mainly used for their analgesic and
sedative properties during surgical
procedures requiring anesthesia.
Opioid drugs: OPIOID AGONIST
9. Alfentanil and Remifentanil
- Is a synthetic opioid
- Less potent and short-acting
- Mainly used for their analgesic and
sedative properties during surgical
procedures requiring anesthesia.
10. Methadone
- Synthetic opioid agonist
- Induces less euphoria and has a longer
duration of action
Opioid drugs: OPIOID AGONIST
11. Meperidine
- Is lower potency synthetic opioid
- Used for acute pain
- Duration of action is slightly shorter
than that of morphine
- Used for short-term management of
pain
Opioid drugs
PARTIAL AGONISTS and MIXED AGONIST-
ANTAGONISTS
1. Buprenorphine
- Is classified as a partial agonist (Mu receptor)
- Naive patients: it acts like morphine
- Abusers: can precipitate withdrawal symptoms
- It causes little sedation, respiratory depression, or
hypotension, even at high doses.
- Administered sublingually, parenterally, or
transdermally
- Has long duration of action
- Tablets are indicated for the treatment of opioid
dependence
Opioid drugs
PARTIAL AGONISTS and MIXED AGONIST-
ANTAGONISTS
2. Pentazocine
- Act as agonist on Kappa receptors but weak
antagonist at Mu and delta receptors
- Promotes analgesia by activating receptors in spinal
cord
- Used to relieve moderate pain
- produces less euphoria compared to morphine
- High dose: respiratory depression and decreases
the activity of the GI tract, increases blood
pressure, can cause hallucinations, nightmares,
dysphoria, tachycardia, and dizziness.
Opioid drugs
PARTIAL AGONISTS and MIXED AGONIST-
ANTAGONISTS
3. Nalbuphine and Butorphanol
- Mixed opioid agonist-antagonists
- They play a limited role in the treatment
of chronic pain
- Butorphanol: available in a nasal
formulation that has been used for
severe headache
Other analgesics
1. Tapentanol
- Is a centrally acting analgesic, an agonist at the Mu
receptor and an inhibitor of norepinephrine reuptake.
- Used to manage moderate to severe pain, both chronic
and acute.
2. Tramadol
- Is a centrally acting analgesic that binds to the Mu
receptor
- Used to manage moderate to moderately severe pain.
- Can lead to toxicity manifested by CNS excitation and
seizures.
Opioid drugs:
Antagonist
1. Naloxone
- Competitive antagonists at Mu, kappa, and delta
receptors
- Used to reverse the coma and respiratory depression
of opioid overdose
- Has a half-life of 30 to 81 minutes
2. Naltrexone
- Action similar to those Naloxone
- Has a longer duration of action
- In combination with Clonidine, is used for rapid opioid
detoxification
OPIATE WITHDRAWAL SYNDROME
Stage I: Up to 8 hours Stage II: Up to 8 to 24 Stage III: Up to 3 days
hours
Anxiety Anxiety Tachycardia
Drug craving Insomnia Nausea, vomiting
GI disturbance Hypertension
Rhinorrhea Diarrhea
Mydriasis Fever
Diaphoresis Chills
Tremors
Seizures
Muscle spasms
Summary of chemical classes of opioid
agonists
Natural Semisynthetic Synthetic
Morphine Hydromorphone Fentanyl
Codeine Hydrocodone Meperidine
Oxycodone Methadone
Oxymorphone Tapentadol
Tramadol
Nursing intervention
• Assess client’s pain before giving medications
• Evaluate effectiveness of analgeisc including
onset and duration of action.
• Observe signs of tolerance with prolonged
use:
a. Tolerance means that a larger dose of narcotic
analgesic is required to produce the original effect.
b. The first sign of tolerance is usually a decreased
duration of effect of the analgesic.
Nursing intervention
• Monitor respiratory rate and depth before
giving drug, and periodically thereafter.
• Encourage sighing, coughing, and deep
breathing.
• Warn ambulatory clients to avoid activities
that require alertness.
• Check for signs of urinary retention
