Pharmacologic Considerations

Although medication use during pregnancy still causes anxiety among the public and health care professionals, two of three women take over-the-counter medications during pregnancy.32 This can result in a woman unknowingly taking a medication that may harm the fetus. Discontinuing medications necessary for treating conditions such as diabetes or infection may harm the fetus as well.33 There is concern the drug will cross the placenta causing teratogenic effects to the fetus and postpartum will appear in the mother’s breast milk with harmful effects to the infant. Most dental procedures are elective and can be postponed until after delivery. However, dental treatment for the pregnant female experiencing oral pain or infection should not be postponed. As mentioned earlier, some women of childbearing age (especially adolescents) may not realize they are pregnant or may conceive while receiving medication. The prescriber should be cognizant of those drugs that are safe during pregnancy and those that may cause teratogenic effects on the fetus when prescribing medication to women of child bearing age.

Teratogenic drugs are medications that may contribute to the development of abnormalities in a developing fetus, i.e., cleft lip or palate, tooth discoloration. The greatest risk to the fetus is from three to eight weeks after conception, during which time the mother may not realize she is pregnant. The potential for teratogenesis and fetal toxicity can occur anytime during pregnancy, as transport of maternal substances to the fetus is established at about the fifth week of pregnancy and continues until birth.

Almost any drug administered to the mother can cross the placental barrier. Drugs of large molecular size and low lipid solubility may have a lower rate and amount of transfer. Drugs of lower molecular weight freely cross the placenta. Acetaminophen, aspirin and most glucocorticoids fall into this category.

Similar precautions should be taken with the breastfeeding mother. The Centers for Disease Control (CDC) reported data regarding the incidence of breastfeeding among U.S. children born in 2011.34 The survey found breastfeeding percentages early postpartum, at six months and 12 months after delivery were 79.2%, 49.4%, and 26.71%, respectively. With these high rates of breastfeeding, health care professionals should be concerned about the potential toxicity of drugs excreted in a mother's breast milk. As with the drugs crossing the placental barrier, the factors that increase the transfer of drugs into breast milk are low molecular weight, low protein binding, high lipid solubility and existing as a weak base.35

For most drugs, infants are exposed to a much higher concentration of drugs during pregnancy than during breastfeeding. Thus, if a drug is deemed acceptable for use during pregnancy, it should be acceptable for use during breastfeeding.

There are strategies to minimize the concentration of drugs in a mother’s milk. If a systemic drug is required while the mother is breastfeeding, practitioners should avoid prescribing sustained-release formulas. In addition the patient is advised to take the medication immediately after breastfeeding, to avoid peak levels during nursing. For medications with a short half-life, mothers can use a pump and discard strategy. For example, the breastfeeding mother receiving local anesthesia during a dental appointment is counseled to pump and save a supply of breast milk before the dental appointment. After the dental appointment the mother pumps and discards the milk and feeds the baby the previously saved milk.

Summary of clinical considerations for medication use in pregnant patients:
  • Use or prescribe medications only if the expected benefits are greater than the potential risks to the fetus.
  • If at all possible, avoid prescribing medication during the patient's first trimester of pregnancy.
  • Prescribe drugs that have been used extensively by pregnant women and not new untested drugs.
  • Prescribe the minimum dose required to achieve the desired effect.
  • Understand the lack of warning on a drug label does not imply safety.
Summary of medical considerations for medication use for breastfeeding patients:33
  • Counsel the patient to minimize the breast fed child's exposure to drugs the mother is receiving by timing feedings or pumping and discarding milk.
  • Understand the potential drug effects to the child and make recommendations to the patient regarding monitoring or responding to these effects.
  • Consider adjusting or limiting dosages during lactation.
  • Recognize the effects of the drug on milk production and clearly explain these effects and consequences to the patient.

The Food and Drug Administration (FDA) created a Pregnancy Risk Classification (PRC) for all approved drugs (Table 1). PRCs A and B can be administered during pregnancy. PRC C drugs may be used with caution. PRC D and X drugs should be avoided. It should be noted, less than 20% of all drugs classified by the FDA are in PRC A or B.15 Table 1 lists commonly prescribed medication prescribed by dental professionals and their PRC category.

Table 1. Medication Considerations during Pregnancy.
Drugs FDA PR* Category Safe During Pregnancy Safe During Breast-feeding
Analgesics and Anti-inflammatories:
Acetaminophen B Yes Yes
Aspirin C/D Avoid Avoid
Codeine C Use with caution Yes
Glucocorticoids
(dexamethasone,
prednisone)
C Avoid Yes
Hydrocodone C Use with caution Use with caution
Ibuprofen C/D Avoid use in 3rd trimester Yes
Oxycodone B Use with caution Use with caution
Antibiotics:
Amoxicillin B Yes Yes
Azithromycin B Yes Yes
Cephalexin B Yes Yes
Chlorhexidine
(topical)
B Yes Yes
Clarithromycin C Use with caution Use with caution
Clotrimazole
(topical)
B Yes Yes
Doxycycline D Avoid Avoid
Erythromycin B Yes Use with caution
Flucozanole C/D Yes (single dose regimens) Yes
Metronidazole B Yes Avoid; may give breast milk an unpleasant taste
Nystatin C Yes Yes
Penicillin B Yes Yes
Tetraconazole
(topical)
B Yes Yes
Tetracycline D Avoid Avoid
Local Anesthetics:
Articaine C Use with caution Use with caution
Bupivicaine C Use with caution Yes
Lidocaine
(with or without
epinephrine)
B Yes Yes
Mepivicaine
(with or without
levonordefrin)
C Use with caution Yes
Prilocaine B Yes Yes
Benzocaine
(topical)
C Use with caution Use with caution
Dyclonine
(topical)
C Yes Yes
Lidocaine
(topical)
B Yes Yes
Tetracaine
(topical)
C Use with caution Use with caution
Sedatives and anxiolytic agents:
Benzodiazepines D/X Avoid Avoid
Zaleplon C Use with caution Use with caution
Zolipedem C Use with caution Yes
Nitrous oxide
with 50% oxygen
1st trimester - No 2nd and 3rd trimesters - use with caution Yes
Emergency Medications:
Albuterol C Steroid and ß2-agonist inhalers are safe Yes
Diphenhydramine B Yes Avoid
Epinephrine B Yes Avoid
Flumazenil C Use with caution Yes
Naloxone C Use with caution Use with caution
Nitoglycerin C Use with caution Use with caution
FDA Pregnancy Risk Categories
Category Definition
A Adequate and well-controlled studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy (and there is no evidence of risk in later trimesters).
B Either (1) adequate and well-controlled studies have failed to demonstrate a risk to the fetus in the first trimester of pregnancy and there is no evidence of risk in later trimesters, but animal reproduction studies have shown an adverse effect on the fetus; or (2) human studies are lacking, but animal studies have failed to demonstrate a risk to the fetus.
C No adequate and well-controlled studies have been performed in pregnant women, but animal reproduction studies are lacking or have shown an adverse effect on the fetus. Potential benefit may warrant use of the drug in pregnant women despite potential risk.
D Positive evidence exists of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in human beings. Potential benefit may warrant use of the drug in pregnant women despite potential risk.
X Studies in animals or human beings have demonstrated fetal abnormalities, and/or there is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience, and the potential risk of the drug in pregnant women clearly outweighs the potential benefit.33
* The most common categories of medications used in dentistry are analgesics, antibiotics and local anesthetics.