Pain pharmacology Flashcards
(21 cards)
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 and 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
What is the mechanism of action for anti-epileptic medications, and for which conditions are they used?
- inhibit neuronal discharge
For neuropathic pain:
- Gabapentin
- Pregabalin
For trigeminal neuralgia:
- carbamazepine
What is the mechanism of action for anti-depressants, and for which (pain) conditions are they used?
Inhibit reuptake of seratonin and noradrenaline at synaptic cleft
SNRI (seratonin and noradrenalin reuptake inhibitors)
TCA (tricyclic anti-depressants)
Can be used as first line defence for neuropathic pain
What is the mechanism of action for muscle relaxants?
Baclofen - stimulates GABA inhibitory neurotransmittor reception at spinal cord, and blocks release of substance P
Diazepam - binds to benzodiazepine receptor and enhances inhibitory actiono of GABA in spinal cord
What is the mechanism of action for corticosteroids?
Mimic effects of endogenous steroid hormone cortisol and disrupts enzymes that regulate inflammatory response
What are the side effects of corticosteroids?
- depression / psychosis
- peptic ulceration
- immunosuppression
- HPA axis suppression
- blood hypercoagulability menstrual disorders
- fever
- cataracts / glaucoma
Safe for children & pregnant women
Which medications are safe and which are contraindicated for pregnant women?
Safe:
- analgesics (opioids, paracetemol, panadol)
- corticosteroids
Contraindicated:
- NSAIDs
