Pregnancy: Therapeutic Considerations

SOURCE

Source: Ward KE. Pregnancy and lactation: therapeutic considerations. In: DiPiro JT, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A Pathophysiologic Approach. 10th ed. New York, NY: McGraw-Hill; 2017. http://accesspharmacy.mhmedical.com/content.aspx?bookid=1861&sectionid=146066717. Accessed May 17, 2017.

DEFINITION

• Therapeutic issues affecting both mother and child, from planning for pregnancy through birth.

PATHOPHYSIOLOGY

• 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 to 1000 D cross more slowly.

  • Molecular weights >1000 D (eg, insulin and heparin) do not cross in significant amounts.

• Lipophilic drugs (eg, opiates and antibiotics) cross placenta more easily than water-soluble drugs.

CLINICAL PRESENTATION

SIGNS AND SYMPTOMS

• Pregnancy-influenced issues.

  • Common during pregnancy:

    • Constipation.

    • Hemorrhoids.

    • Gastroesophageal reflux disease (GERD)

    • Nausea/vomiting.

  • 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.

  • Allergic rhinitis.

  • Asthma.

  • Diabetes mellitus.

  • Epilepsy.

  • HIV infection.

  • Hypertension.

  • Depression.

• Labor and delivery.

  • Preterm labor.

  • Group B Streptococcus infection.

  • Cervical ripening and labor induction.

  • Labor analgesia.

DIAGNOSIS

• Refer to individual disorders for diagnostic considerations.

DESIRED OUTCOMES

• 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)