Pharmacology

• The liver is the primary organ responsible for drug metabolism.
• First-line therapies for mild pre-eclampsia:

  • Methyldopa
  • Hydralazine
  • Labetalol
  • Widely used and safe for pregnant mothers
• Additional drug alternatives for gestational hypertension:

  • Prazosin
  • Nifedipine
  • Clonidine
• Betablockers are safe, but there is a potential for impaired fetal growth if used early in pregnancy
• Magnesium Sulfate (MgS04) is used for severe pre-eclampsia for the prevention of eclampsia
• Adverse reactions for Methyldopa:

  • Peripheral Edema
  • Anxiety
  • Nightmares
  • Drowsiness
  • Headache
  • Dry mouth
  • Drug-induced fever
  • Mental depression
• Adverse reactions for Hydralazine:

  • Headaches
  • Nausea & vomiting
  • Nasal congestion
  • Dizziness
  • Tachycardia
  • Palpitation
  • Angina pectoris
  • No known direct effect on fetus
• Adverse reactions of Magnesium Sulfate:

  • Early signs of increased Magnesium levels include:
  • Lethargy
  • Flushing
  • Feelings of increased warmth
  • Perspiration
  • Thirst
  • Sedation
  • Heavy eyelids
  • Slurred speech
  • Hypotension
  • Decreased DTR (deep tendon reflex)
  • Decreased muscle tone
• Therapeutic Magnesium levels are 4-7 mEq/L
• Loss of patellar reflexes is the first sign of Magnesium Toxicity
• Toxic level of MgS04 is 8-10mEq/L
• Respiratory Depression can be manifested if the level of MgS04 in the blood is 10-15mEq/L
• Cardiac arrest may occur if the MgS04 level in the blood becomes 20-25 mEq/L
• Nursing interventions for MgS04:

  • Provide continuous electronic fetal monitoring
  • Monitor fetal toxicity
  • Have antidote (Calcium Gluconate) always available at bedside
  • Maintain patient in left lateral recumbent position
  • Use Z-tract technique for IM injection of MgS04 and rotate sites of injection
  • Monitor BP, PR, RR, DTR, I&O every hour
  • Monitor temperature, breath, and bowel sounds every 4 hours
  • Check urine for protein every hour
  • Monitor serum MgS04 level range should be between 4-7mEq/L
  • Assess for epigastric pain, headache, visual disturbances
• Nursing interventions for Hydralazine:

  • Monitor BP frequently
  • Observe for maintenance of diastolic BP between 90 and 110mm Hg as ordered
  • Observe for the level of consciousness and headache
  • Monitor I and O
  • Monitor Fetal Heart Rate
• Tocolytic therapy is indicated for pregnant clients experiencing Preterm Labor (PTL)
• Mechanism of action is to decrease premature uterine contractions using terbutaline sulfate and Magnesium Sulfate (MgS04)
• Other drugs that can be used for tocolytic therapy are Indomethacin and nifedipine
• Terbutaline is initially given at 0.25mg every 20 minutes to 6 hours if the maternal pulse is less than 120 beats per minute
• Adverse reactions of terbutaline sulfate include tremors, dizziness, nervousness, tachycardia, hypotension, chest pain, palpitations, nausea, vomiting, hyperglycemia, and hypokalemia
• Terbutaline sulfate is contraindicated in patients with cardiac disease, poorly controlled hyperthyroidism, or diabetes mellitus
• Magnesium Sulfate (MgS04) is a calcium antagonist and CNS depressant that relaxes the smooth muscle of the uterus
• Magnesium Sulfate is safe to use, has less side effects, is excreted by the kidneys, crosses the placenta, increases uterine perfusion, and has therapeutic effects on the newborn
• Adverse reactions of Magnesium Sulfate include flushing, feelings of increased warmth, perspiration, dizziness, and watch out for toxicity symptoms such as respiratory depression, cardiac arrest, and depressed reflexes
• Nursing interventions during tocolytic therapy include monitoring vital signs, fetal heart rate, uterine activity, intake and output, breath and bowel sounds, deep tendon reflexes, pain, uterine contractions, weight, serum MgS04 levels, and observing the newborn for effects if the drug is given to the mother before delivery
• Corticosteroid therapy in preterm labor
• The desired outcome of tocolytic therapy is to delay birth to allow time for corticosteroids to reach maximum benefit
• Pregnant clients at 24-34 weeks are at risk for preterm delivery and should receive betamethasone or dexamethasone
• Mechanism of action of betamethasone and dexamethasone is to accelerate fetal lung maturation and lung surfactant development, decreasing the incidence of respiratory distress syndrome and increasing survival of preterm infants
• Betamethasone dose is 12mg intramuscularly every 12 hours for 2 doses
• Dexamethasone dose is 6mg intramuscularly every 12 hours for 4 doses
• Side effects of betamethasone include seizures, headache, vertigo, edema, hypertension, increased sweating, petechiae, ecchymoses, and facial erythema
• Fetal and maternal daily requirement for iron during pregnancy is 27mg/day
• Goal in giving iron supplement is to prevent maternal iron deficiency anemia and not to supply the fetus with iron
• Recommended iron demand during pregnancy:

  • 1st trimester: 6.4mg/day
  • 2nd trimester: 18.8mg/day
  • 3rd trimester: 22.4mg/day
• Pregnant patients generally have decreased hematocrit early in the 3rd trimester, if below 30%, the iron dosage must be increased
• Common side effects of taking iron preparations:

  • Nausea & vomiting
  • Constipation
  • Black, tarry stools
  • GI irritations
  • Epigastric pain
  • Discoloration of urine
  • Diarrhea
• Nursing considerations for iron:

  • Dilute iron with water and use a straw when giving liquid iron to prevent staining of teeth
  • Iron is best absorbed with juice and on an empty stomach
  • Vitamin C increases iron absorption
  • If there would be gastric irritation, iron may be administered with food
  • Do not administer iron with milk, cereal, tea, coffee, or eggs
  • Do not mix antacid with iron, give iron 2 hours before or 4 hours after antacid
• Folic acid is recommended to prevent spontaneous abortion and neural tube defects

  • Recommended to be given 1 month before conception and for the 1st 2-3 months after conception at 0.4mg - 0.8mg
  • Folate-rich foods like green leafy vegetables, asparagus, papaya, strawberries, and oranges should also be given
• Adverse reactions to folic acid:

  • Rash
  • Allergic bronchospasm
  • Pruritus
  • Erythema
  • Malaise
  • Urine may turn intensely yellow