Chapter 8 - Pharmacotherapy During Pregnancy

Question 1

Drug Use in Pregnancy and Lactation

Answer 1

• Nurse responsible for health/safety of pregnant person and fetus
• Most drugs cross placenta and secreted in breast milk.
• Despite fetal risk, 90% of pregnant persons take at least one drug during pregnancy; 80% take one drug during 1st trimester.
• HCP are cautious when prescribing drugs in pregnancy, harm may occur at any stage of pregnancy.
  
  • Use increased with maternal age
  • Certain acute or chronic conditions must be managed with medication
    
    • Goal is to treat a pregnant person without harming the fetus.
    • Consider the therapeutic value of drug balanced against the potential adverse effects.

Question 2

Third trimester

Answer 2

Many drugs cause problems in third trimester

• SSRI link to low Apgar scores, high rates of admission to special care nursery, and neonatal symptoms of respiratory distress, jitteriness, and hypoglycemia.
• Unknown if this is r/t toxicity or withdrawal.
• If possible, meds should be postponed until after delivery and lactation when possible.
• Safer alternatives should be used

Question 3

Physiological changes: Pharmacokinetics - Absorption

Answer 3

Physiological changes during pregnancy can alter normal pharmacokinetic responses

• Absorption: Increased levels of progesterone cause a decrease in gastric tone and intestinal motility - delayed gastric emptying
  
  • drugs remain longer in GI tract
  • extended time for absorption
• High estrogen causes increased hydrochloric acid production in the stomach - may affect absorption of certain acid labile drugs
• The pressure of stomach by the growing fetis leads to slower gastric emptying
  
  • longer time to absorb and distributed - prolonging their onset and duration
• Progesterone increases pulmonary blood flow leading to increased levels of respiratory drugs.

Question 4

Physiological changes: Pharmacokinetics - Distribution

Answer 4

Total body water increases by 50% - greater hemodilution of plasma proteins and drugs

• Plasma proteins are diluted and fewer are available to bind with drugs causing a higher concentration of “free” drug in plasma
• More drug molecules are available for transfer across the placenta or secreted into breast milk
  
  • highly lipophilic drugs distributed into the lipid-rich breast milk and passed to infant
• Womens HR may increase up to 15 beats per minute - greater drug distribution

Question 5

Physiological changes: Pharmacokinetics - Metabolism

Answer 5

• Affected by enzyme changes
• Cytochrome P450 enzyme:
  
  • CYP2D6 and CYP3A4 increase
  • CYP1A2 decrease
• Fetal liver still developing and unable to metabolize drugs

Question 6

Physiological changes: Pharmacokinetics - Excretion

Answer 6

Enhanced by renal plasma flow - increase 50% - 70% during first two trimesters

• Higher glomerular filtration rate and decrease blood urea nitrogen (BUN) and creatine levels
• Increased renal elimination of drugs
• Increased blood volume r/t hemodilution may increase medication loss – need higher dose of med

Question 7

Placenta Function During Pregnancy

Answer 7

• Prevents harmful substances from reaching fetus
• Vitamins, fatty acids, glucose, electrolytes freely pass from the pregnant person to the fetus
• Most drugs cross placenta by simple diffusion
• Few drugs cross by way of active transport
• Drugs don’t have to cross placenta or enter fetal blood to cause fetal abnormalities
• Higher drug dose taken by pregnant person, more drug circulates through placenta.
  
  • Rationale to give lowest effective dose.
• Factors effecting drug transfer across placenta include solubility, molecular size, protein-binding and ionization.

Question 8

PharmFACT

Answer 8

The most common antidepressants, the selective serotonin reuptake inhibitors (SSRIs), when taken by pregnant person, have been shown to increase the risk of preterm labor and may cause withdrawal symptoms in newborns that include agitation, irritability, trouble feeding, sleep disturbances, and convulsions (Saccone, Eke, & Berghella, 2016).

Healthcare providers have been advised to taper dosages of SSRIs during the third trimester so that fetus receives no drug through the placenta for at least 7 to 10 days prior to birth.

Question 9

The US Food and Drug Administration - Pregnancy Risk Categories

Answer 9

Used as guidelines in prescribing medications during pregnancy

• Pregnancy categories - rate medication based on their risk during pregnancy
  
  • Review table in book - Created from animal lab tests and only approximates
  • Category A and B are considered safe
  • Category C make up about ⅔ of prescriptions
    
    • insufficient data to decide whether the drug is safe
      
      • avoid
  • Category D and X - avoid as they have the potential to cause birth defects

No prescription drug, OTC medication, or herbal product should be taken during pregnancy unless prescribed by healthcare provider.

Question 10

Encouraged Drugs

Answer 10

• Multivitamins and iron to increase metabolic demands placed on the mother
  
  • Vitamin B9 (folic acid) - found to prevent fetal spinal cord defects

Question 11

Drugs to Avoid

Answer 11

• Isotretinoin used for acne can lead to brain damage. Misoprostol may lead to abortion.
• ACE inhibitors known to lead to IUGR and fetal demise.
• Tetracyclines and other ABX lead to teeth staining.
• Other B/P meds may cause renal atrophy.
• Thalidomide r/t limb loss.
• Negative effects of alcohol, illicit drugs and nicotine.

Question 12

Limitations of Current Pregnancy Classification

Answer 12

• No specific clinical information on drug safety.
• System does not indicate how drug should be adjusted
  during pregnancy or lactation.
• FDA addressing issues by updating categories with more descriptive information
• New System began June 2015 and includes Pregnancy and Lactation Labeling Rule (PLLR)
  
  • Subsections and a reproductive potential subsection.
  • New labeling began in 2015 with all new drugs old drugs to be changed gradually
• Better patient-specific counseling and informed decision-making for pregnant persons seeking medications

Question 13

Pharmacotherapy During Lactation

Answer 13

• Adverse drug effects during lactation
• Even with small concentrations (< 3%), effects in infants can be serious
• Nonspecific effects may be diarrhea/constipation, sedation, irritability
• All Illicit drugs contraindicated
  
  • SUD (substance use disorder) Med Rx encouraged
• Topical medications in general are safe
  
  • Vitamins A,E or D in creams rubbed on nipples may be passed to infant
• Herbal supplements should be avoided during pregnancy
• National Institute of Health (NIH) database LactMed – update drug exposures monthly in breastfeeding persons.
  
  • Provides clinical data on drug effects on baby during lactation.