General about opioids

Question 1

Endogenous opioid peptides

Answer 1

Enkephalins
β-endorphins
Dynorphins

Question 2

Opioid receptors

Answer 2

μ - most therapeutic effect.
δ
κ - some mixed opioid agonists-antagonists

Question 3

Types of opioid drugs (classification)

Answer 3

Full agonists (strong or moderate)
Mixed agonist-antagonists
Pure antagonists

Question 4

Pure antagonists - clinical use

Answer 4

Counteract adverse effects of opioid overdose and treatment of dependence.

Question 5

Opioids - MOA

Answer 5

Activate opioid G protein-coupled receptors. Inhibition of adenylyl cyclase, decreased cAMP, increased K conductance and decreased Ca conductance.
Presynaptic inhibition of neurotransmitter release from central terminations of small-diameter primary afferent fibers.
Postsynaptic inhibition of membrane depolarization of the dorsal horn nociceptive neurons.

Question 6

CNS effects of opioids

Answer 6

Analgesia
Sedation
Euphoria/dysphoria
Miosis (direct stimulation of Edinger-Westphal nucleus in oculomotor nerve)
Nausea, vomiting
Respiatory depression, inhibition of cough reflex.

Question 7

Diagnostic sign for opioid overdose

Answer 7

Miosis - little or no tolerance develops to this

also little tolerance to constipation

Question 8

Cardiovascular effects of opioids

Answer 8

Vasodilation (histamine release from mast cells).
Orthostatic hypotension (decreased PVR and baroreceptor reflex).
Reduction in cardiac work and myocardial oxygen demand (beneficial in CAD)

Question 9

GI, biliary and genitourinary system effects of opioids

Answer 9

Increase smooth muscle muscle tone.
Inhibition of peristalsis and constipation.
Increased tone of sphincter of Oddi (biliary) - exacerbation of pain/gallbladder attack in biliary dysfunction.
Urinary retention.

Question 10

Which opioid has less effect on smooth muscle constriction? And when is it used?

Answer 10

Meperidine. Preferred in labor.

Question 11

Other effects of opioids

Answer 11

Release of ADH and prolactin, inhibit release of LH.

Suppress certain lymphocytes (NK cells)

Question 12

Opioids - adverse effects

Answer 12

Respiratory depression by reducing the hypercapnic drive.
Increased intracranial pressure.
Nausea and vomiting.
Flushing, itching/pruritus by release of histamine from mast cells.
Allergic reactions - usually not cross-sensitivity

Question 13

Opioids - contraindications

Answer 13

Closed-head injury.