test 5 opioids Flashcards
Pain
- Acute or chronic unpleasant sensation
- Result of complex neurochemical processes in the peripheral and central nervous system
- Subjective
- Management is one of medicine’s greatest challenges
Opioids
- Natural, semisynthetic, or synthetic compounds that produce morphine-like effects
- Act by binding to specific opioid receptors in CNS to produce effects that mimic the action of endogenous peptide neurotransmitters
Natural Opioids “Opiates” come from
• Opium poppy seed pod
Opioid Use and abuse
- Primary use: relieve intense pain from surgery, injury or chronic disease
- Abuse
* Widespread availability
* Euphoric properties - Antagonists exist to reverse the actions
Opioid Effects
• G protein coupled receptors Inhibit adenylyl cyclase
• Decrease presynaptic Ca2+ influx (decreases neurotransmitter at the synaptic vessible)
• Increase postsynaptic K+ efflux (hyperpolarization)
- IMPEDES NEURONAL FIRING AND TRANSMITTER RELEASE
Opioid Effects Mediated by 3 receptor families
Mu μ
• Analgesia via modulating nociception: thermal, chemical, and mechanical
• High affinity for morphine
Kappa κ
• Analgesia via modulating nociception: thermal and chemical
Delta δ
• Regulate nociception
• High affinity for enkephalins (peptide released in brain)
Opioid Adverse Effects
- hypotension
- dysphoria (anxiety, depression)
- sedation
- constipation
- urinary retention
- nausea
- potential for addiction
- RESPIRATORY DEPRESSION
Opioids differ in
- Receptor affinity
- Pharmacokinetics
- Available routes of administration
- Adverse effect profiles
Morphine
- Major analgesic drug in crude opium
- Strong μ agonist
- Mechanism of Action: interacts with opioid receptors on membranes of cells in CNS, GI tract and bladder
* ↓ release of substance P (modulates pain perception in spinal cord)
* Inhibits release of excitatory transmitters from nerve terminals carrying painful stimuli
Morphine Actions
- Analgesia
* ↑ pain threshold at spinal cord level
* Alters brain’s perception of pain - Euphoria
- Respiratory depression
* Most common cause of death in acute overdose
* Tolerance develops quickly - Depression of cough reflex
- Miosis
* Important for diagnosis of overdose
* No tolerance develops - Emesis
- Decreased GI motility
* Constipation with little tolerance developing - Cardiovascular
* Low dose: no major effects on BP or HR
* High dose: hypotension and bradycardia - Histamine release
* Urticaria, sweating, vasodilation, bronchoconstriction - Increases ADH
* Urinary retention - Prolongs labor
* Decreases strength, duration and frequency of contractions
Morphine Pharmacokinetics
- Significant 1st pass effect
* IM, SQ, IV
* Oral: slow and erratic absorption - Rapidly enters all body tissues, including fetus
- Metabolized in liver, excreted in urine
- DOA: 4-5 hours
- Special populations
* Neonates- cannot metabolize
* Elderly- more sensitive, lower starting doses
Morphine Adverse Effects
- Severe respiratory depression
- Tolerance and physical dependence
* Tolerance develops in all aspects EXCEPT pinpoint pupils and constipation
Codeine
- Weak analgesic found in crude opium
- Converted to morphine in the liver
- Commonly used with acetaminophen for pain
- Good antitussive (stop a cough)
* Removed from over the counter preparations due to abuse
Semisynthetic Derivatives of Morphine
- Oxycodone (Oxycontin)
* Oral (2x analgesia of morphine)
* Abuse of sustained release preparations has resulted in many deaths - Hydromorphone (Dilaudid)
* Oral (8-10x more potent than morphine)
Semisynthetic Derivatives of Codeine
- Hydrocodone (Vicodin)
* Oral analgesic effect=morphine
