Path pharmacology Flashcards
State and explain the method of medication prescription
Recognise – individual and cultural influences – impact on community – benefits andreview of management
Assess – site, severity and cause – classification
Treat – non-pharmacological – pharmacological – WHO ladder for cancer pain – WHO reverse ladder for severe acute pain – anti neuropathies – appropriate use of opioids
State the three classifications of pain
- Acute or chronic/ persistent
- Nociceptive (specific stimulus of pain) or neuropathic (no specific stimulus identified, damage to nerve or nervous system)
- Cancer or non-cancer
What do analgesic agents do to reduce pain?
-Altering perception of pain in central nervous system
- inhibiting local production of pain mediators
- interrupt neural impulses in spinal cord
Need awareness of how analgesic regimes work
What is bupicacaine?
Longer term local anaesthetic
- Post operative pain relief to reduce reliance on
Slow onset of action – 30 minutes so used alongside opioids during operation (eg. Diamorphine and/or fentanyl.)
What is a reversal agent?
any drug used to reverse the effects of anaesthetics, narcotics or potentially toxic agents
What is a local anaesthetic?
-cause reversible sensory block to nerve conduction providing analgesia to patient (can cause motor block)
- sodium channels of nerve membrane a receptor for local anaesthetic molecule
- If excessive amounts in systemic circulation – symptoms and signs of toxicity may appear (must be monitored)
- Clearance almost entirely due to liver metabolism
What is fentanyl?
-Synthetic opioid with my-agonist pharmacological effects
- Clinical potency of 50-100 times that of morphine
- primarily used in analgesia and sedation for adults with moderate to severe pain
- rapid onset of action and duration of action is short
- highly lipid soluble
- redistributed to other tissues and released into blood – up to 80% bound to plasma proteins
- metabolised by liver and excreted mainly in urine
- large inactive metabolites
- reversed by naloxone – opioid antagonist
What is naloxone?
Reversal agent for all opioids
What is morphine?
-Relief of severe acute pain in adults
Oral opioid
-As effective as more invasive routes if equianalgesic doses administered
- First line choice when treating severe acute pain
- little evidence in why they are useful in management of long term pain
- should always receive lowest dose providing effective pain control
- opioid analgesic – act on receptors in CNS
- competitive agonist in my receptors mediating other action of respiratory depression, euphoria, inhibition of gut motility and physical dependence
- rapid onset of action – peak analgesic effect within 20 minutes
- same metabolism and excretion as oral doses
Why is morphine very widely used?
- Concentration 2mg/ml is schedule 5 drug meaning not controlled drug – does not require 2 person check so very easy to be dispensed
- other conc. Schedule 2 controlled drug with tighter restrictions (IV then step down oral)
What is PCA?
Patient control analgesia
patient control of pain relief – relevant when patient has been on opioid previously (not opioid naïve)
Explain the absorption of morphine
-Extensive first pass metabolism in liver
– result in systemic bioavailability 25-33%
-10mg morphine equates to 3 mg IV
- Important to consider in slinical when stepping down from parenteral routes
Explain the metabolism of morphine
-Mainly liver
- conjugation to morphine 3 and 6 glucuronides
- Particular in M6G (morphine-6-Glucuronide)
- half life of morphine 2 hours but M6G longer
How is morphine excreted?
Urine
- Reduced renal function delayed clearance allow drug and metabolites to continue to exert effect
Monitoring essential
What are the contraindications of morphine?
-Sensitivity to morphine
- respiratory depression
- renal disease
- reduced sedation, drug interactions, enzyme inducers e.g. rifampicin (decreasing effect), enzyme inhibitors e.g. cimetidine (increasing effect), CNS depressant
