Pain pharmacology Flashcards
What are the 2 major types of pain relieving medications, and the 4 sub-types?
Analgesics - alleviate pain (opioids/ narcotics and non-narcotics)
Anti-inflammatories - reduce the inflammatory response (NSAIDs & corticosteroids)
What are examples of medications for each of the 4 sub-types of pain medication?
Opioids -Panadeine, Endone, Oxycodone
Non-narcotic analgesics - Paracetemol, Pandol
NSAIDs - Nurofen, Ibuprofen, Voltaren, aspirin
Corticosteroids (steroidal anti-inflammatories)
What are the potential side effects of opioid analgesics?
- high addictive potential
- respiratory depression (can be fatal)
- hallucinations
- hypothermia
- constipation
- nausea / vomiting
- drowsiness
What are the side effects of non-narcotic analgesics?
- liver damage (because metabolized in liver)
- kidney damage
Which populations are contraindicated for the use of non-narcotic analgesics ie: paracetemol and panadol?
Patients with high alcohol intake or liver/kidney damage - non-narcotic analgesics can damage the liver & kidney because they are metabolized by these organs
What are examples of non-narcotic analgesics?
Paracetemol
Panadol
What are examples of opioid analgesics?
Panadeine Endone Oxycodone morphine heroin fentanyl
What are examples of non-steroidal anti-inflammatories (NSAIDs)?
Nurofen (ibuprofen)
Voltaren (diclofenac)
Aspirin
What are side effects of NSAIDs?
Non-selective NSAIDs:
- GI distress
- hypertension
- kidney injury
- impaired renal drug metabolism
- stroke
- myocardial infarction
Which side effects are specific to aspirin?
- tinnitus (overdose)
- Reye’s syndrome in children - causes encephalopathy
(aspirin contraindicated for children)
What is the mechanism of action of opioids?
In the PNS:
- binds to peripheral nociceptor, causing hyperpolarization & making nerve less likely to generate an action potential transmitting pain signal
In the spinal CNS (dorsal horn):
- inhibits release of nociceptive transmission from 1st order neuron
- hyperpolarizes 2nd order neuron and makes it less likely to generate an action potential
In the supraspinal CNS:
- activates descending neural pathways
- alters perception of pain
- induces euphoria
What are the mechanisms of non-narcotic analgesics?
Poorly understood - believed to act upon prostaglandin synthesis in the CNS
What are the mechanisms of NSAIDs?
- inhibit COX enzymes that synthesize prostaglandins (role in inflammation & pain pathway)
COX1: role in inflammatory response & also homeostatic functions / GI protection
COX2: role in inflammatory response
Selective COX inhibitors inhibit COX2 only (less chance of GI distress and disruption of homeostatic function)
What are the 4 types of alternative medications used for pain reduction, and examples of each?
Anti-epileptics (Gabapentin, Pregabalin)
Anti-depressants (Amitryptyline, SSRI)
Muscle relaxants (Baclofen, Diazepam, Valium)
Local anaesthetic
What is the mechanism of action for local anaesthetic?
- interferes with conduction of nerve impulses in sensory neurons by blocking influx of sodium to cell membranes
