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Pain Management - Coggle Diagram
Pain Management
Morphine
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Strong affinity for μ receptors, varying affinities for κ & δ
CNS effects: analgesia, euphoria, sedation
Histamine release: vasodilation, itching, bronchoconstriction
NO CEILING DOSE: titrate upwards until pain is relieved (10mg 4hrly for 24hrs, titrate up in increments of 30-50% if necessary)
Adverse events: nausea (initially, resolves, metoclopramide 10mg 8hrly), sedation (resolves after few days), constipation (prescribe stool softener), respiratory depression
Caution: renal & hepatic impairment, elderly, pregnant, lactation, neonates, decreased pulmonary reserve (COPD, acute asthma)
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NB to consider: tolerance, withdrawal symptoms, addiction
NSAIDs
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Contraindications: hypersensitivity to NSAIDs, active peptic ulceration
Caution in renal & hepatic impairment, history of dyspepsia, cardiac failure, HPT, bleeding disorders, asthma
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Adverse effects: bronchoconstriction, fluid retention, nephorpathy & ARF, bleeding, hypersensitivity, dyspepsia & peptic ulceration, hepatotoxicity
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Tramadol
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MOA: dual action, parent drug & active metabolite are μ receptor agonists + inhibits serotonin & noradrenalin reuptake
Adverse events as with morphine, but less abuse potential, resp depression & constipation
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Dose: starting 50mg 4-6hry, max 400mg/day (adjust in renal impairment)
Drug interactions: predisposes to serotonin syndrome when combined with SRI or MAOIs, metabolism induced by carbamazepine
Synergistic analgeisic with paracetamol
Codeine phosphate
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CYP2D6 variants: slow metaboliser (poor analgesic effect but constipation), rapid metaboliser (resp depression, coma, death)
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Chronic Pain
Visceral: pleurisy, cancer pain
Neuropathic: abnormal neural activity to disease or injruy to the nervous system (e.g. diabetic neuropathy, drug-induced peripheral neuropathy, trigeminal neuralgia, post-herpetic neuralgia)
Somatic: arthritis, fibromyalgia, lower back pain
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Pain lasting beyond the term of an injury or painful stimulus, present from more than 4-6 weeks
Non-opiods
Non-opioids
Paracetamol, NSAIDs (non-selective & selective COX-2 inhibitors)
Weak opiods
Tramadol, Codeine phosphate
Strong opiods
Morphine, Pethidine, Fentanyl
Assessment of pain
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Comprehensive assessment using pain assessment tools (1-10, faces)
Types of pain
Nociceptive
Normal pain processing that occurs when free nerve endings are activated by tissue damage or inflammation
4 processes: transduction, transmission, perception & modulation
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Adjuvant therapy
Tricyclic antidepressants (TCAs): amitriptyline, imipramine
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Indications: antidepressant, analgesic, anxiolytic, sedative
Dose (amitriptyline) : 10-25mg nocte, titrate up to 75mg nocte
Anticonvulsants: carbamazepine. valproic acid, gabapentin, pregabalin
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