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Two categories of drugs for pain relief
- Opioids
- Non-opioid analgesics
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Opioid Analgesics
- Naturally occurring, semisynthetic, synthetic agents that relieve moderate to severe pain
- Bind to specific neuronal receptors that are located in the CNS
- Potential to cause dependence
- Controlled substances
- Narcotic
- ----Have sedative or sleep inducing response and high doses cause unresponsiveness and stupor
- Opiate
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Sources of opioids
- Synthetic
- ----Basic chemical components
- Semisynthetic and natural
- ----Opium poppy
- --------20 active compounds
- ------------Morphine
- ------------Codeine
- ----Does not contain an analgesic effect
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Endogenous Opioids
- Receptors in brain and SC for exogenous substances
- Released during stressful situations and interact with other neurochemicals and immune system to deal with various physical and psychosocial stress; pain
- Three distinct families
- ----Endorphins
- ----Enkephalins
- ---- Dynorphins
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Three classes of opioid receptors
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Mu
- Most important in mediating analgesic effect of many opioids
- ----Ex: morphine
- Located in brain and SC
- Side effects
- ----* Leads to cellular change and possible opioid abuse and addiction
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Kappa/ delta
- More selective in receptor class or subclass they stimulate
- Don’t have as strong side effects, can block mu receptors
- Mixed agonist- antagonist opioids
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Opioid classifications
- Strong agonists
- Mild-mod agonist
- Mixed agonist- antagonists
- Antagonists
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Strong agonists
- Treat severe pain
- High affinity for certain receptors interact primarily with mu opioid receptors in CNS
- Ex: Methadone (Dikiohine, methadose)
- Morphine (MS Contin, Roxanal, Statex)
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Mild-to-moderate agonists
- Treat pain of moderate intensity
- Exe: codeine
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Mixed agonists-antagonists
- Act differently at specific receptors
- ----Some agonist and antagonist like activity at the same time
- Produce adequate analgesia with less risk of side effects
- Less addictive
- Ex: nalbuphine (Nubain)
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Antagonists
- Blocks opioid receptors (especially mu affinity)
- treat opioid overdose and addiction
- Ex: naloxone (Narcan)
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