10-17 CNS
Chapter 10 Analgesic Drugs
Pain Management
Analgesics
Medications that relieve pain without causing loss of consciousness
Opioid analgesics
Adjuvant analgesic drugs
Pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage
Exists when the patient says it exists
Pain Threshold: Level of stimulus needed 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 functionSubjective 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 Tolerance Physical dependence Classification of Pain Somatic Visceral Superficial Deep Vascular Referred Neuropathic Phantom Cancer Central Audience Response System Question #1 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 E. NOTE: No input is required to proceed. A. Answer to System Question #1 ANS: A 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 9 10 11 12 1/11/20253that 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. Pain Transmission Tissue injury causes the release of the following: Bradykinin Histamine Potassium Prostaglandins Serotonin These substances stimulate nerve endings, starting the pain process. Pain Transmission (Cont.) 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.) Closing of the gate is affected by the activation of A fibers. This causes the inhibition of impulse transmission to the brain and avoidance of pain sensation. Opening of the gate is affected by the stimulation of C fibers. Pain Transmission (Cont.) Body has endogenous neurotransmitters. Enkephalins Endorphins Released whenever the body experiences pain or prolonged exertion Bind to opioid receptors Inhibit transmission of pain by closing gate Pain Transmission (Cont.) Rubbing a painful area with massage or liniment stimulates A large sensory fibers. Result Closes gate Reduces pain sensation Treatment of Pain in Special Situations PCA and “PCA by proxy” (when family presses button instead of pt -> overdose) Patient comfort vs. fear of drug addiction 13 14 15 16 17 18 19 13 14 15 16 17 18 19 1/11/20254Patient comfort vs. fear of drug addiction Opioid tolerance Use of placebos Recognizing patients who are opioid tolerant (use extended-release oxycodone) Breakthrough pain: occurs between doses of pain medications due to analgesic effects wear offSynergistic effect -> adjuvant drugs Adjuvant Drugs Assist primary drugs in relieving pain NSAIDs Antidepressants Anticonvulsants Corticosteroids Example: adjuvant drugs for neuropathic pain Amitriptyline (antidepressant) Gabapentin or pregabalin (anticonvulsants) World Health Organization Three-Step Analgesic Ladder Step 1: nonopioids (with or without adjuvant medications) after the pain has been identified and assessed. If pain persists or increases, treatment moves to Step 2: opioids with or without nonopioids and with or without adjuvants. If pain persists or increases, management then rises to Step 3: opioids indicated for moderate to severe pain, administered with or without nonopioids or adjuvant medications. Opioid Drugs Synthetic drugs that bind to the opiate receptors to relieve pain Mild agonists: codeine, hydrocodone Strong agonists: morphine, hydromorphone, oxycodone, meperidine, fentanyl, and methadoneMeperidine: not recommended for long-term use because of the accumulation of a neurotoxic metabolite, normeperidine, which can cause seizures Opioid Ceiling Effect Drug reaches a maximum analgesic effect. Analgesia does not improve, even with higher doses. Pentazocine Nalbuphine Opioid Analgesics: Mechanism of Action Three classifications based on their actions Agonists Agonists-antagonists Antagonists (nonanalgesic) Agonists Bind to an opioid pain receptor in the brain Cause an analgesic response (reduction of pain sensation) 20 21 22 23 24 25 20 21 22 23 24 25 1/11/20255Agonists-Antagonists Bind to a pain receptor Cause a weaker neurologic response than a full agonist Also called partial agonist or mixed agonist Antagonists Reverse the effects of these drugs on pain receptors Bind to a pain receptor and exert no response Also known as competitive antagonists Equianalgesia Ability to provide equivalent pain relief by calculating dosages of different drugs or routes of administration that provide comparable analgesia Hydromorphone (Dilaudid): seven times more potent than morphine Example: if morphine 10 mg was given to a patient followed 1 hour later by hydromorphone 1 mg, then the patient would have received an equivalent of 17 mg of morphine. Opioid Analgesics: Indications 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: Contraindications Known drug allergy Severe asthma Use with extreme caution in patients with: Respiratory insufficiency Elevated intracranial pressure Morbid obesity or sleep apnea Paralytic ileus Pregnancy Audience Response System Question #2 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. Which vital sign is of greatest concern? A. Pulse B. Blood pressure C. Temperature D. Respirations E. 26 27 28 29 30 31 26 27 28 29 30 31 1/11/20256E. NOTE: No input is required to proceed. Answer to System Question #2 ANS: D This patient has a history of asthma and allergies, and she will be receiving a drug that can depress respirations. 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) Constipation Itching 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). 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 Audience Response System Question #3 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. What do 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 opioidC. An uncaring attitude toward the patient D. A failure to manage the patient’s pain properly E. 32 33 34 35 36 37 32 33 34 35 36 37 1/11/20257E. NOTE: No input is required to proceed. A. Answer to System Question #3 ANS: D 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. Opioid Analgesics: Toxicity and Management of Overdose (Cont.) Opioid withdrawal or 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 Others Codeine Sulfate Opioid agonist Natural opiate alkaloid (Schedule II) obtained from opiumLess effective Ceiling effect Often combined with acetaminophen Schedule III More commonly used as an antitussive drug Most common adverse effect: GI disturbance Fentanyl Synthetic opioid (Schedule II) used to treat moderate to severe pain Parenteral injections, transdermal patches (Duragesic), buccal lozenges (Fentora), and buccal lozenges on a stick (Actiq) 38 39 40 41 42 43 38 39 40 41 42 43 1/11/20258lozenges on a stick (Actiq) Fentanyl in a dose of 0.1 mg intravenously is roughly equivalent to 10 mg of morphine intravenously. Fentanyl patch for chronic, long-term pain management Hydromorphone (Dilaudid) Hydromorphone: very potent opioid analgesic; Schedule II drug One milligram of IV or IM hydromorphone is equivalent to 7 mg of morphineExalgo: Osmotic extended release oral delivery Difficult to crush or extract for injection which aids in reducing abuse potential Meperidine Synthetic opioid analgesic (Schedule II) Caution with use in elderly or those with kidney dysfunction Active metabolite (normeperidine) can accumulate to toxic levels and cause seizuresRarely used and not recommended for long-term pain treatment Use: Migraine treatment Post-op shivering Methadone Hydrochloride (Dolophine) Synthetic opioid analgesic (Schedule II) Opioid of choice for the detoxification treatment of opioid addicts in methadone maintenance programs Prolonged half-life of the drug: cause of unintentional overdoses and deaths Cardiac dysrhythmias Morphine Sulfate Naturally occurring alkaloid derived from the opium poppy Drug prototype for all opioid drugs; Schedule II controlled substance Indication: severe pain High abuse potential Oral, injectable, and rectal dosage forms; also extended-release forms Oxycodone hydrochloride Analgesic agent structurally related to morphine Class II Comparable analgesic activity to morphine Often combined with acetaminophen (Percocet) or with aspirin (Percodan) IR = immediate release SR = sustained release Hydrocodone (weaker) often combined with acetaminophen (Vicodin, Norco) Opioid Agonists-Antagonists Mixed action Schedule IV: Lower risk of misuse or addiction 44 45 46 47 48 49 44 45 46 47 48 49 1/11/20259Schedule IV: Lower risk of misuse or addiction Not strong enough to manage longer term chronic pain Should not be given concurrently with full opioid agonists Ex: Buprenorphine (Buprenex) Butorphanol (Stadol) Nalbuphine (Nubain) Pentazocine (Talwin) Naloxone Hydrochloride (Narcan) Pure opioid antagonist Drug of choice for the complete or partial reversal of opioid-induced respiratory depressionIndicated in cases of suspected acute opioid overdose Failure of the drug to significantly reverse the effects of the presumed opioid overdose indicates that the condition may not be related to opioid overdose. Opioid Antagonists Naloxone now available without a prescription and is being used by 1st responders for opioid/illegal drug overdoses Naltrexone Opioid antagonist Oral form Used for alcohol and opioid addiction Nonopioid Analgesics: Acetaminophen (Tylenol) Analgesic and antipyretic effects Little to no antiinflammatory effects Available over-the-counter (OTC) and in combination products with opioids Acetaminophen: Mechanism of Action Similar to salicylates Blocks pain impulses peripherally by inhibiting prostaglandin synthesis Acetaminophen: Indications Mild to moderate pain Fever 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 older adults and 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). Audience Response System Question #4 50 51 52 53 54 55 56 50 51 52 53 54 55 56 1/11/202510 Answer to System Question #4 ANS: B Chronic heavy alcohol abusers may be at increased risk of liver toxicity from excessive acetaminophen use. For this reason, a maximum daily dose of 2000 mg is generally recommended for these persons. Acetaminophen: Contraindications and 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 other drugs that are hepatotoxic. Acetaminophen: Toxicity and Managing Overdose Even though available OTC, 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 Tramadol Hydrochloride Trade name: Ultram Centrally acting analgesic with a dual mechanism of action Weak bond to mu opioid receptors Inhibits the reuptake of norepinephrine and serotonin) Indicated for moderate to moderately severe pain Adverse effects similar to those of opioids Careful use in patients taking SSRIs, MAOIs, neuroleptics Lidocaine, transdermal Topical anesthetic Indications: postherpetic neuralgia Left in place no longer than 12 hours Minimal adverse effects Skin irritation may occur Analgesics: Nursing Process: Assessment 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. 57 58 59 60 61 62 57 58 59 60 61 62 1/11/202511Assess for potential contraindications and drug interactions. Analgesics: Nursing Process: Assessment (Cont.) 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 Use appropriate scale for age, cognition Analgesics: 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; be sure to include other interventions as indicated. Analgesics: Nursing Implications (Cont.) Patients should not take other medications or OTC preparations without checking with their physicians. Instruct patients to notify physician about signs of allergic reaction or adverse effects. 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 (Cont.) 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.) 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. Opioid Analgesics: Nursing Implications (Cont.) 63 64 65 66 67 68 69 63 64 65 66 67 68 69 1/11/202512Monitor 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 (Cont.) 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) Herbal Products: Feverfew 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, as well as anticoagulants