Medication Safety Labeling
Historically, manufacturers have relied on an alphabetical system to communicate the safety of medications for use with pregnant patients (Table). In 2015, the U.S. Food & Drug Administration began phasing out that system for prescription drugs, replacing it with a narrative section in the package insert that discusses the benefits and risks of using a particular medication with this population.8 The new system will be phased-in, with a full compliance date of 2020.
The alphabetical system (Table) will continue to be used for over-the-counter medications9.
Table. Pregnancy Risk Categories10
| Category A
|| Controlled studies show no risk
| Category B
|| No evidence of risk in humans
- Adequate well-controlled studies in pregnant women have not shown
increased risk of fetal abnormalities despite adverse findings in animals.
- In the absence of human studies, animal studies showed no fetal risk.
The chance of fetal harm is remote but remains a possibility.
| Category C
|| Risk cannot be ruled out
- Adequate well-controlled human studies are lacking, and animal studies have
shown a risk to the fetus or are lacking as well. There is a chance of fetal harm
if administered during pregnancy, but the potential benefits
may outweigh the potential risk.
| Category D
|| Positive evidence of risk
- Studies in humans, or investigational or post-marketing data,
have demonstrated fetal risk. Nevertheless, potential benefits
from use of this drug may outweigh the potential risk.
For example, the drug may be acceptable
if needed in a life-threatening situation or serious
disease for which safer drugs cannot be used or are ineffective.
| Category X
|| Contraindicated in pregnancy
- Studies in animals or humans, investigational or post-marketing reports,
have demonstrated positive evidence of fetal abnormalities or
risk that clearly outweighs any possible benefit to the patient.
Questions about the local anesthetics or antibiotics used in dentistry are common. Options considered safe for use in these situations include:
- Local anesthesia (with or without epinephrine)1, 11, 12
- Antibiotics11, 12, 13
Use of other medications calls for consultation with the patient’s obstetrician to weigh risks and benefits. An example of a situation that may benefit from consultation is pain relief. Several analgesics have been placed in pregnancy Category B, which indicates that they are typically safe to use; however, in 2015, the U.S. Food & Drug Administration backed off that classification, stating that the published research is “too limited to make any recommendations” on pain reliever use in this population.14 This suggests that decisions made about medications for pain relief should be arrived at after consultation with the obstetrician. That said, emergencies call for immediate implementation of standard emergency protocols.
Questions often arise about medication use by patients who are lactating. Most medication product inserts have information related to use during lactation. The National Library of Medicine also provides a searchable database (LactMed) on this topic.
Nitrous oxide is classified as a pregnancy risk group Category C medication, meaning that there is a risk of fetal harm if administered during pregnancy. It is recommended that pregnant women, both patients and staff, avoid exposure to nitrous oxide.15 The National Institute of Occupational Safety and Health (NIOSH), a federal agency affiliated with the Centers for Disease Control and Prevention, recommends use of a scavenging system and exposure limits of N2O concentrations in dental operations to approximately 25 ppm during analgesia administration.16
Dental offices that use nitrous oxide-oxygen can review best management practices on the Nitrous Oxide page.