Flashcards in General about opioids Deck (13)
Endogenous opioid peptides
μ - most therapeutic effect.
κ - some mixed opioid agonists-antagonists
Types of opioid drugs (classification)
Full agonists (strong or moderate)
Pure antagonists - clinical use
Counteract adverse effects of opioid overdose and treatment of dependence.
Opioids - MOA
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.
CNS effects of opioids
Miosis (direct stimulation of Edinger-Westphal nucleus in oculomotor nerve)
Respiatory depression, inhibition of cough reflex.
Diagnostic sign for opioid overdose
Miosis - little or no tolerance develops to this
(also little tolerance to constipation)
Cardiovascular effects of opioids
Vasodilation (histamine release from mast cells).
Orthostatic hypotension (decreased PVR and baroreceptor reflex).
Reduction in cardiac work and myocardial oxygen demand (beneficial in CAD)
GI, biliary and genitourinary system effects of opioids
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.
Which opioid has less effect on smooth muscle constriction? And when is it used?
Meperidine. Preferred in labor.
Other effects of opioids
Release of ADH and prolactin, inhibit release of LH.
Suppress certain lymphocytes (NK cells)
Opioids - adverse effects
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