Wk 6: Pain management Flashcards
What types of drugs work on the perception?
- paracetamol
- opoids
- anti depressants
- MORNRI
What types of drugs work on the modulation?
- antidepressants: SNRI, SSRI, TCA
What types of drugs work on transmission?
- opioids
- local anesthetic
What should be considered when deciding on medication to give?
Types of pain
Acute pain: related to opoidergic system
Persistent pain: associated with neuropathic
What types of drugs work for nociceptive pain?
- NSAIDs
- opioids
What types of drugs work for neuropathic pain?
First line:
- antidepressants
- anticonvulsants
- topical agents
What are adjuvant agents?
= medications that aren’t typically used for pain but may be helpful due to their mechanism of action.
- sometimes have have analgesic properties.
- act on substance P and other NTs
Include
- muscle relaxants
- antidepressants
- anticonvulstants
Why might adjuvant agents be used?
- for neuropathic pain
- to supplement other typical pain medication use
- to reduce opooid side effects by reducing the demanded dose needed to reduce pain
- as a primary therapy again pain
- control symptoms and thus again reduce analgesuc requirements
Explain the use of paracetamol
Simple anaglesic and antipyretic
- mild ot moderate pain
- can be used for many ages
- many routes
- considered in the step 1 of WHO analgesic pathway
- good for soft tissue and MSK pain
- supplement opioids to reduce the need for high doses and thus reduce symptoms.
Mechanism of action
- not fully known
= evidence suggests it effects CNS and works on a lower part of the prostaglandin production.
Prostoglandins are involved in pain transition
- forms a components and reduces the reuptake of canabnoids.
Explain NSAIDS
- mild to moderate pain
Use: MSK and tissue injury
- muscle aches
- headache
- low back pain
- osteoarthritis
- tissue sprains
Action
- inhibit synthesis of prostaglandins at a higher level in the chain of production than panadol.
Cox 1: renal bloood vessel and stomach
Cox 2: present in most cells of stomach and at sight of injury.
Coxibs: new NSAIDS spring in Cox 2 so there is less irritation in the stomach as this is where they are primarily found.
What are some examples of non selective NSAIDS
Ibuprofen (Nurofen - oral)
Naproxen (Naprosyn - oral)
* Diclofenac (Voltaren - oral)
* Indomethacin (Indocid -
oral/PR)
* Ketorolac (Toradol - IM / IV)
- high risk of gastric irritation
Effect Cox 1 and 2 so can cause gastric irritation
What are some examples of Cox-2 specific NSAIDS
Celecoxib (Celebrex – Oral)
What are some examples of long acting NSAIDS
Meloxicam (Mobic - Oral)
- long acting NSAID
- good for arthritis
Preferential but not Cox 2
Explain opoids
Moderate to sever
Acute or persistant
- great in multimodal use
MOA: acts as agonists at receptor sites in the brain, spinal cord and other sites of the CNS thus blocking the brains ability to perceive pain.
Instead they stimulate the plaseure centeres of the brain and induce euphoria
3 primary recpetors:
- mu (μ), delta (δ) and kappa (Ќ)
- Analgesia is mediated mainly via the μ receptor
How does morphine work?
- activation of opoid receptor in the neuron
- release in Gabba which causes neighbouring cells release dopamine
- Gabba binds to the nociceptor
- activation of the opioid receptor cause a change in the cells ad inhibits the production of subsatnce P so no transmission can occur in synaptic cleft and thus modulated pain perception
= works to dull the pain and block the signals getting to the presynaptic neuron on the noceptor.
What are some of the most common opoids and what are their routes of administration, indications and points of pratice?
Morphine: most commonly used, various routes
Fentanyl: rapid action; strong; often used for simple and fast procedures; cancer pain; various routes
Oxycodone: oral; used as a step down agent from IV opioids
Hydromorphone: 5 x potent as morphine; various routes; used in cancer and palliative situations
Methadone: oral, long action; for persistent pain, used for substance users to transition from addiction; often daily doses
Pethidine: less used, offers no advantage over other opioids;
Codeine: oral with other drugs e.g. paracetamol
Buprenorphine: SL, IM, SC, TD; long action, used for substance users to transition from addiction; often daily doses
Explain tramadol
= synthetic, weak opioid with multiple actions
1) works on opoid MU receptors
2) Enhances noradrenergic (40%) inhibition
3) Enhances serotonergic (20%)
inhibition
- moderate pain
As it is a weak opoid;
- Reduced incidence of respiratory depression
- Lower abuse potential
- Less constipating
ROA: Oral/parenteral
Explain ketamine
= NMDA antagonist (N‐methyl‐D‐aspartate)
- corsses the blood brain barrier for acute onset pain relief.
- Dissociative anaesthetic agent as causes various effects in mood and etc
- hallucinations, panic attacks, paranoia
- Ketamine treatment effective for relief of postoperative pain
- For acute and persistent pain
- Often used with an opioid for improved analgesia & opioid sparing. Then don’t get the extra effects of ketamine
Explain canabis
Acts on the CNS
- becoming more mainstreem trestment
= acts on the canaboid receptors of the brain
- canabnoids and turpines (active ingredients) are delivered though the blood stream, digestive, lungs, topical.
- bind with receptors to suptess signs including pain, nausea, depression and boost signals of euphoria and apetite.
Cannabinoids bind with the endocannabinoid
receptors, suppress signals such as pain, nausea and
depression, boost signals of appetite and euphoria.
- still being studied
- for people with presistent pain while it reduced the need for opoids it did not show anything to reduce long term use.
Explain anticonvulsants
e.g.gabapentin or pregabalin
= modulate neurotransmitter release
- reduction is neurotransmitter activity and thus helps with neuronal pain.
- Modulates neurotransmitter release by binding to voltage
gated Ca++ channels - Closes pre-synaptic Ca++ channels
- Diminishes excessive neuronal activity and neurotransmitter release
Used for neuropathic pain, post-heretic neuralgia, diabetic
neuropathy, fibromyalgia
Explain antidepressants
= work on the block of serotonin and noradrenaline + adrenaline and histamines.
- used in a lower dosage for pain
- reduced delay of action
Category includes: tricyclic antidepressants (TCAs),
selective serotonin reuptake inhibitors (SSRI) and serotoninnorepinephrine reuptake inhibitors (SNRIs).
Explain MORNRI
e.g. Tapentadol
Mu-opioid receptor agonist (MOR) + noradrenaline
reuptake inhibition(NRI)= (MOR-NRI)
- Both mechanisms contribute to the analgesic activity
to produce analgesia in a synergistic manner - Relatively moderate activity at the two target sites is
sufficient to produce strong analgesic effects. - Used for both nociceptive and neuropathic pain
- reduction in physical dependance and reduced level of gastric impacts