Analgesic DrugsAnalgesics- Medications that relieve pain without causing loss of consciousnesso Moderate to severe pain- “Painkillers”- Opioid analgesics- Adjuvant analgesic drugso Enhance effect or to assist with pain relief Pain- 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 existsNociception- Pain results from stimulation of sensory nerve fibers called nociceptors- These receptors transmit pain signals from various body regions to the spinal cord and brainPain Threshold- Level of stimulus needed to produce the perception of pain- A measure of the physiologic response of the nervous systemPain Tolerance- 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, ethnicityClassification of Pain by Onset and Duration- Acute paino Sudden onseto Usually subsides once treated- Chronic paino Persistent or recurringo Lasts 3 to 6 monthso Often difficult to treatClassification of Pain- Somatic – muscle/skeletal- Visceral – organ pain - Superficial – sharp, tingly- Deep – deep somatic pain- Vascular –neuropathy, like a constant pin prick - Referred – common in hospital pain, appendicitis, gall stones- Neuropathic – stroke pt, sharp- Phantom – in an extremity that has been amputated - Cancer – anywhere- Central – CNS pain, pins and needles 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 systemPain Transmission- Tissue injury causes the release of:o Bradykinino Histamineo Potassiumo Prostaglandins o Serotonin- These substances stimulate nerve endings, starting the pain process- 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- 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 neurotransmitterso Enkephalinso 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- Resulto Closes gateo Reduces pain sensationTreatment of Pain in Special Situations- 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 effectAdjuvant Drugs- Assist primary drugs in relieving paino NSAIDso Antidepressantso Anticonvulsants –sedatives o Corticosteroids – if the inflammation is causing the pain - Example: Adjuvant drugs for neuropathic paino amitriptyline (antidepressant)o gabapentin or pregabalin (anticonvulsants)Opioid Drugs - Synthetic drugs that bind to the opiate receptors to relieve pain- Very strong pain relieversOpioid Ceiling Effect- Drug reaches a maximum analgesic effect- Analgesia does not improve, even with higher doseso pentazocineo Nalbuphine  Mimic opioid, safe to use in pt. that are addicted  Partial antagonists  Synthetic Opioid Analgesics - Examples: o codeine sulfateo meperidine HCl (Demerol) – potential to cause more side effectso methadone HCl (Dolophine) – rehab of subs. abuse ptso morphine sulfate – use IVo hydromorphoneo fentanyl (Duragesic) most potent o oxycodoneo Others- Mechanism of Action:o Three classifications based on their actions: Agonist – produce response Partial agonist – partial response Antagonist – counteract the opioid- Indicationso Main use: to alleviate moderate to severe paino Often given with adjuvant analgesic drugs to assist primary drugs with pain reliefo Opioids are also used for: Cough center suppression –codeine  Treatment of diarrhea Balanced anesthesia- Contraindicationso Known drug allergyo Severe asthma Itching is a normal side effecto Use with extreme caution in patients with: Respiratory insufficiency Elevated intracranial pressure- Don’t give narcotics  Morbid obesity and/or sleep apnea Paralytic ileus – bowel that is not moving - Can cause constipation  Pregnancy- Crosses placental barrier - Adverse Effectso CNS depression Leads to respiratory depression- Most serious adverse effecto Nausea and vomitingo Urinary retentiono Diaphoresis and flushingo Pupil constriction (miosis)o Constipation o Itching- Toleranceo A common physiologic result of chronic opioid treatmento Result: larger dose is required to maintain the same level of analgesia- Physical Dependenceo Physiologic adaptation of the body to the presence of an opioido Opioid tolerance and physical dependence are expected with long-term opioid treatment and should not be confused with psychologic dependence (addiction)- Psychologic Dependenceo 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- Toxicity and Management of Overdoseo naloxone (Narcan) o naltrexone (ReVia)o Regardless of withdrawal symptoms, when a patient experiences severe respiratory depression, an opioid antagonist should be given.o Opioid withdrawal/opioid abstinence syndromeo Manifested as:  Anxiety, irritability, chills and hot flashes, joint pain, lacrimation, rhinorrhea, diaphoresis, nausea, vomiting, abdominal cramps, diarrhea, confusion- Interactionso Alcohol – number one o Antihistamines – the ones that cause drowsinesso Barbiturateso Benzodiazepineso Monoamine oxidase inhibitors- Nursing Implications o Oral forms should be taken with food to minimize gastric upseto Ensure safety measures, such as keeping side rails up, to prevent injuryo 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/mino Check dosages carefullyo Follow proper administration guidelines for IM injections, including site rotationo Follow proper guidelines for IV administration, including dilution, rate of administration, and so