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Source: Ward KE, O’Brien
BM. Pregnancy and Lactation: Therapeutic Considerations. In: DiPiro
JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach.
8th ed. http://accesspharmacy.com/content.aspx?aid=7992979.
Accessed June 8, 2012.
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- Therapeutic issues affecting both mother and child, from
planning for pregnancy through birth.
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- Delayed gastric emptying and vomiting may alter drug absorption
during pregnancy.
- Increased gastric pH may affect absorption of weak acids and
bases.
- Higher estrogen and progesterone levels may alter liver enzyme
activity and increase elimination of some drugs but accumulation
of others.
- Maternal plasma volume, cardiac output, and glomerular filtration
increase by 30–50% during pregnancy, possibly
lowering plasma concentration of renally cleared drugs.
- Increased body fat may increase volume of distribution of
fat-soluble drugs.
- Reduced plasma albumin concentrations may increase volume
of distribution of highly protein-bound drugs; however, unbound
drugs more rapidly cleared by liver and kidneys.
- Placenta is organ of exchange between mother and fetus for
a number of substances, including drugs.
- Drug molecular weights affect drug transfer across placenta:
- Molecular weights >500 daltons (D) cross readily.
- Molecular weights from 600–1000 D cross more slowly.
- Molecular weights >1000 D (e.g., insulin and heparin) do not
cross in significant amounts.
- Lipophilic drugs (e.g., opiates and antibiotics) cross placenta
more easily than water-soluble drugs.
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- Pregnancy-influenced issues
- Common during
pregnancy:
- Hyperemesis gravidarum (severe nausea/vomiting causing
weight loss >5% of prepregnancy weight and ketonuria) occurs
in 1–3% of pregnant women.
- Gestational diabetes mellitus (GDM) more common in African
Americans, Native Americans, Asian Americans, Hispanic Americans,
and Pacific Islanders.
- Hypertension, including:
- Gestational hypertension:
Pregnancy-induced hypertension without proteinuria
- Preeclampsia: Hypertension with proteinuria
- Eclampsia: Preeclampsia with seizures (medical emergency)
- Chronic hypertension: Diagnosed prior to pregnancy with or
without overlying preeclampsia
- Venous thromboembolism (VTE), with risk factors in pregnancy
of:
- Increasing age
- History of thromboembolism
- Hypercoagulable conditions
- Operative vaginal delivery or cesarean section
- Obesity
- Family history of thrombosis
- Acute care issues that may arise in pregnancy
- Headache
- Urinary tract infections
- Sexually transmitted infections (STIs)
- Chronic illnesses that may occur in pregnancy
- Labor and delivery
- Preterm labor
- Group B Streptococcus infection
- Cervical ripening and labor induction
- Labor analgesia
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- Refer to individual disorders for diagnostic considerations.
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- Provide preconception interventions to help ensure optimal
pregnancy outcomes.
- Relieve symptoms associated with pregnancy-influenced medical
disorders.
- Prevent congenital malformations caused by medication exposure.
- Goals for GDM:
- Fasting plasma glucose <90–99
mg/dL (5–5.5 mmol/L)
- 1-hour postprandial plasma glucose concentrations 140 mg/dL
(7.8 mmol/L) or less
- 2-hour postprandial glucose <120–127 mg/dL
(6.7–7 mmol/L)
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- Principles for selecting medications during pregnancy:
- Select drugs used safely for long periods.
- Prescribe doses at lower end of recommended range.
- Eliminate nonessential medication and discourage self-medication.
- Avoid medications known to be harmful.
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- Encourage folic acid intake (400 mcg/day) by
all women of childbearing potential to reduce risk for neural tube
defects in offspring.
- Avoiding alcohol, tobacco, and other substances prior to pregnancy
improves outcomes.
- For constipation during pregnancy, before drug therapy attempt: ...