Lecture 6: Opioid Agonists and Antagonists Flashcards
1
Q
Three main subtypes of Opioid Receptors?
A
Mu (u), Kappa (K), and Delta
2
Q
Higher affinity
- Mu Receptor?
- Kappa?
- Delta?
A
- Endorphins > Enkephalins > Dynorphins
- Dynorphins»_space; endorphins and enkephalins
- Enkephalins > endorphins and dynorphins
3
Q
- At the Presynaptic Terminal, Mu and Kappa and delta receptors do what 2 things?
- At Postsynaptic Neuron, Mu receptors cause what to occur?
A
- Decrease gCa2+, and decrease transmitter release (ACH, NE, Glutamate, 5HT, Substance P)
- Increase gK+ and thus an IPSP (producing hyperpolarization and inhibition of postsynaptic neurons)
4
Q
- Activation of Mu Receptors produces 3 effects of opiates, as well as what else?
A
- Analgesic, Euphoric, and Sedative effects, as well as most of their UNTOWARD SIDE EFFECTS
5
Q
- Activation of KAPPA Receptors may contribute to what?
a. Esp in whom?
b. Frequently causes what?
c. Drugs that bind to KAPPA Receptors may have what?
A
- ANALGESIA
a. in Women
b. DYSPHORIA
c. a Lower Addiction Potential
6
Q
Delta and Sigma, may contribute to what effects of Opiates?
a. Which is NOT an OPIOD RECEPTOR?
A
Dysphoric
a. SIGMA
7
Q
- Afferent Pain neurons cross midline of spinal cord and ascend in what 2 tracts?
A
Spinoreticular or Spinothalamic Tracts which Synapse in different regions of the THALAMUS
8
Q
Overall Effects of Opioid Agonists
- Inhibition of what Pain Transmitting Systems?
- Stimulation of what systems?
- important binding sites of Opiates are found in what pathways?
- Inhibition of what pathway that would normally decrease activity of the Descending pain inhibition pathway.
- Systemic Administration of Opioids may also cause a release of what?
A
- Ascending Pain Transmitting Systems
- of Descending Systems that inhibit pain transmission
- in Descending pathways that modulate pain transmission (rostral ventral medulla, locus coeruleus, midbrain periaqueductal gray)
- of Inhibitory neurons (GABA)
- of Endogenous opioids which could contribute to and enhance the overall effect of the drug
9
Q
Pharmacological Actions of Opioids
- Antitussive Effect
a. Doses needed to SUPPRESS cough are how than those need for ANALGESIA?
b. Which drug is most often used for this?
c. What other drug could also be used?
d. WHAT drug DOES NOT SUPPRESS COUGH?
A
- a. Generally Lower
b. CODEINE
c. DEXTROMETHORPHAN
d. MEPERIDINE does NOT SUPPRESS COUGH
10
Q
Pharmacological Actions of Opioids
- What patients SHOULD NOT be GIVEN MORPHINE?
- Pupillary Constriction (MIOSIS) is seen with ALL OPIOIDS EXCEPT?
- What Opiate may Cause TACHYCARDIA due to ANTICHOLINERGIC ACTIVITY?
A
- Those with HEAD TRAUMA or INCREASED INTRACRANIAL PRESSURE!
- MEPERIDINE (Constriction is usually a sign of OPIOID OVERDOSE)
- MEPERIDINE
11
Q
Pharmacological Actions of Opioids
- GI: Most common effect?
a. What 2 other things may occur?
A
- CONSTIPATION is common.
a. DECREASED GASTRIC MOTILITY and BILIARY COLIC may occur due to constriction of biliary muscle
12
Q
Tolerance and Physical Dependence
- Tolerance may develop due to persistent stimulation of what receptor?
- What receptor Antagonist may prevent tolerance from occurring?
- HYPERALGESIA may also occur. What does this mean?
- TOLERANCE may develop to SOME OF THE EFFECTS of OPIOIDS (like what) but not to others?
A
- of the MU Receptors or possibly uncoupling of receptors to G-proteins
- NMDA receptor Antagonist
- Sensation of pain is actually INCREASED in patients who take opioids chronically.
- Analgesia, sedation, euphoria, nausea; but not to Miosis or Constipation
13
Q
Adverse Effects
- Side effects are generally EXTENSIONS of their pharmacologic Actions. They INCLUDE what 8 things?
A
- Abuse and Addiction frequently occur; Constipation (treat for it when opioid use is initiated); Itching; Nausea and Vomiting; Physical Dependence; Respiratory Depression and Urinary Retention (w/ benign prostatic hyperplasia)
14
Q
- Addiction may be more likely if how much opioids are given?
A
- If they’re underprescribed or prescribed too infrequently.
15
Q
- the ABSTINENCE SYNDROME can be Precipitated by Tx w/what?
A
- w/an OPIOID ANTAGONIST in PHYSICALLY DEPENDENT PATIENTS