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36 Cards in this Set
- Front
- Back
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oxytocin physiology
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polypeptide hormone released by the posterior pituiatry
plays a role in normal labor and normal milk ejection reflex |
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oxytocin chemistry
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inactivated by proteolytic enzymes when given orally
structurally similar to ADH |
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oxytocin must be administered
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parenterally
can be by IV, IM injection, buccal tablets, nasal spray |
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oxytocin half-life
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very short
5 to 10 minutes |
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oxytocin metabolized and inactivated by enzymes found in the
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liver and kidneys
cleave bond between cysteine and tyrosine |
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during pregnancy, oxytocin inactivatin occurs in
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plasma, uterus, and placenta
lactating mammary gland also inactivates oxytocin |
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oxytocin effects on smooth muscle of the uterus
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stimulates both electrical and contractile activity of uterine smooth muscle
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oxytocin receptor is a ________ receptor which acts via this pathway
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G-protein linked receptor
acts via the phosphatidylinositol pw |
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oxytocin receptor activation leads to
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increased PLP-C
increased activity of slow Na channels calcium mobilization activation of myosin light chain kinase |
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non-pregnant uterus and oxytocin
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NP uterus is very resistant to oxytocin but strong contractions can be produced by high concentrations
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during the 1st two trimesters of pregnancy
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you can stimulate the uterus but it takes very high concentration of oxytocin
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as a female approaches term
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oxytocin sensitivity of the uterus greatly increases
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problems ass. with the high doses required to produce strong contractions during 1st and 2nd trimester
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some of the SEs are increased since they are not dependent upon the endocrine state
contractions are not well coordinated higher doses often result in tetanic contractions |
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oxytocin and the mammary glands
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produces contraction of the myoepithelium which forces milk into the large ducts
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CV effects of oxytocin
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oxytocin produces a transient relaxing effect on vascular smooth muscle resulting in transient hypotension
with extended infusion of oxytocin, the brief fall in blood pressure is followed by a small but sustained increased in BP |
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oxytocin effects on the kidney
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has some ADH activity
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AA ergot alkaloids are not used because
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they can't be given orally
there is a latent period before response even when given IV they are extremely toxic |
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methylergonovine may be given
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orally or parenterally
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onset of action of methylergonovine
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almost immediate after IV administration
rapidly absorbed after oral of IM administration and the onset of action is w/in minutes |
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duration of actin of methyergonovine
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3-6 hours
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methylergonovine effects on the uterus
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increases force and frequency of contraction
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methyergonovine CV effects
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can cause transient but severe HTN
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summary of oxytocin properties
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orally ineffective
duration of action--- minutes small increase in resting tone well coordinated contractions stimulates mammary epi cells increased sensitivity of uterus at term |
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summary of methylergonovine effects
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orally effective
DOA-- several hours large increase in resting tone poorly coordinated contractions doesn't stimulate mammaries increased sensitivity of uterus at term |
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main toxic effect of oxytocin
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rupture of uterus
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FDA says oxytocin should no longer be used for
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elective induction of labor
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adverse effects of oxytocin
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uterine hypertonicity
uterine rupture fetal bradycardia possible premature delivery |
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indications for induction of labor
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Rh blood problems
maternal diabetes preeclampsia ruptured membranes |
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drug that should be used to overcome prolonged uterine inertia
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oxytocin
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drug that should be used to induce therapeutic abortion
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PGEs
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PGE SEs
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nausea, vomiting, cramps, diarrhea
HTN bronchospasm uterine rupture |
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drug that should be used to control post-partum hemorrhage
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oxytocin, ergonovine, methylergonovine
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drug that should be used after C-section
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oxytocin, ergonovine, or methylergonovine
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drug that should be used during uterine surgery
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oxytocin, ergonovine, or methylergonovine
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drug used to promote lactation
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oxytocin
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oxytocin challenge test
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IDs fetus at risk due to placental insufficiency
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