12. Opioids, anti-NGF monoclonal antibodies Flashcards
(16 cards)
What are opioids?
Opioids are a class of drugs used to reduce moderate to severe pain.
They are classified by how they interact with opioid receptors in the body
Name the opioid receptors
- Full agonist
- Full antagonist
- Partial agonist
- Agonist-antagonist
What is a full agonist
They bind strongly to mu receptors and activate them fully, producing a strong opioid effect
What is a full antagonist
The drugs block major opioid receptors, preventing them from being activated by other opioids
What is a partial agonist
The drugs bind to mu receptors, but do not activate them as fully, resulting in a weaker effect
What is a agonist-antagonist?
The drugs have a mixed effect, acting as agonists at kappa receptors and antagonists at mu receptors.
Agonists = activators, antagonists = blockers
Full agonist, Active substances
Morphine
Fentanyl
Full antagonist, Active substances
Naloxone
Partial agonist, Active substances
Buprenorphine
Agonist-antagonist, Active substances
Butorphanol
Mechanism of action of opioids
The opioids bind to endorphin receptors, mainly mu, kappa and delta.
- Mu-opioid receptors
when they bind to these receptors, we get a specific and strong analgesic effect, slight sedation, slowed breathing, decreased heart rate, constipation and sometimes nausea and vomiting
- Kappa-opioid receptors
Binding here leads to a mild analgesic effect, slight sedation and dysphoria
- Delta-opioid receptor
These are mostly for analgesia, especially if the eye is injured.
Pharmacokinetics of opioids
1. Absorption
Good – excellent.
Some drugs, such as morphine, are affected by the “first-pass effect” when taken orally, which means that the liver breaks down a lot of the drug before it can circulate throughout the body.
Fentanyl: Due to it being very lipophilic (fat-soluble), it can be absorbed through the skin
2. Distribution
How quickly can the drug reach maximum effect:
fentanyl = 2-3 min
Morphine = 15-45 min
Buprenorphine = 45 min
3. Metabolism
in the liver.
4. Tramadol
How tramadol can vary a lot between dogs and cats.
Dogs: Oral bioavailability can vary significantly (4-65%) and is metabolised into O-desmethyl-tramadol.
Cats: Excrete tramadol quickly through glucuronidation.
There are big individual differences in how tramadol works, especially when given orally to dogs.
Side effects of opioids
-
Respiratory depression
Full agonists have a stronger effect than partial agonists. -
Emesis
Morphine causes less, tramadol has the highest emesis side effect -
Bradycardia
Important to mention cardiovascular risk patients. Cats have a stronger sympathetic tone -
Obstipation
Inhibition of the myenteric plexus and decreased pancreatic secretion are involved.
Morphine
Causes sedation, respiratory repression, bradycardia, emesis
Fentanyl
Causes sedation, respiratory depression, and bradycardia
Buprenorphine
Respiratory depression, “ceiling effect”, meaning a higher dose does not always bring more pain relief.
What is NGF (Nerve Growth Factor) Monoclonal antibodies
NGF monoclonal antibodies are special drugs that target the nerve growth factor.
What is NGF (Nerve Growth Factor) Monoclonal antibodies, Active substances
- Bedinvetmab
- Frunevetmab
How does NGF (Nerve Growth Factor) Monoclonal antibodies work?
The NGF monoclonal antibodies help nerves in a few ways:
1. Developing nervous system
They help nerves grow and develop properly
They keep the sympathetic and sensory neurons alive and working
2. Adult nervous system
They play a role in how adults feel pain
Nociception and pain modulation, meaning they change how the body senses pain and potentially reduce it.
Short: These antibodies can interfere with nerve growth factors, which can impact nerve development, survival and pain sensation
