It is important to note that almost every substance used for therapeutic purposes can and does pass from the mother to the fetus; the concept of a “placental barrier” is a misnomer. Of greater importance is whether the rate and extent of transfer are sufficient to result in significant concentrations within the fetus to cause either teratogenicity or fetotoxicity. The aim when prescribing in pregnancy is to balance the risks of potential adverse effects of the drug (usually to the fetus) with the benefit (usually to the mother) of treating the disease. This balance may change during the pregnancy depending on the disease activity and the gestation. In general, there is insufficient reliable information available with regard to the safety during pregnancy of herbal medications, so the general recommendation is to avoid using these supplements during this important 9-month period. For most drugs, the infant is exposed to a much higher concentration during pregnancy than during breastfeeding. Therefore, if a drug is considered acceptable during pregnancy, it is usually reasonable to continue taking it during breastfeeding (Henderson & Mackillop, 2011). However, there are exceptions, and the most important factors are the concentration of the drug in the infant’s blood and the effects that this concentration of the drug might have. Small molecules get into breast milk more easily than large molecules (e.g., heparin is not excreted in breast milk). Furthermore, the half-life of some drugs in the neonatal circulation may be longer than in the mother, because infant liver metabolism is immature. This factor may lead to accumulation of the drug in the infant and is especially true of morphine, lamotrigine, phenobarbital, some benzodiazepines, and aspirin (Briggs & Freeman, 2014; Hale, 2002; Liporace, Kao, & D’Abreu, 2004; Rutherford, 2008). For some medications with a short half-life, the “pump and discard” strategy can be effective. This is best demonstrated with the recently popular enteral sedation drug triazolam (Howie & McMullen, 2006; Lee, 2007). The lactating mother is counseled to pump and save milk before the dental appointment. She takes triazolam before the dental appointment to help ameliorate her anxiety, and for the next 8 to 10 hours after the dental appointment (four half-lives), she will pump and discard the milk, while feeding her baby with the milk she had pumped and saved from the previous day. After the four half-lives have passed, she can then return to her regular breastfeeding schedule. It takes approximately four half- lives for more than 90% of most medications to be eliminated from the body (Winter, 2010). In general, there is insufficient reliable information available with regard to the safety of herbal medications in breastfeeding, so the general recommendation is to avoid using these supplements during this critical time period. prescribed by OHCPs can be given without regard to many herbal-drug interactions, there are definitely exceptions, which this course has described in detail, as well as outlining strategies for the practicing dentist to help keep the patient safe. Access to and use of clinical evidence databases as described herein can help prevent risk of herbal-drug interactions.
the top 20 most common herbal medications that OHCPs are likely to encounter and their traditional FDA pregnancy risk factor categories are listed in Table 10. It is important to note that the lettered system is being phased out, and the letters are no longer being placed on the packaging of new drugs (FDA, 2016). The system came to be considered too simplistic and easily misinterpreted (Johnson, 2016). By the year 2020, no drug will use this system (Johnson, 2016). Table 10: The Top 20 Most Common Herbal Medications that OHCPs are Likely to Encounter and their U.S. Food and Drug Administration Pregnancy Risk Factor Categories*
Pregnancy Risk Factor Category Herbal
Pregnancy Risk Factor Category
Herbal
Elderberry
D Saw palmetto X Ashwagandha
X X C D
Horehound
Cranberry
D Green Tea
Turmeric
D Ivy Leaf
Apple cider vinegar
D Ginkgo
X
Cannabidiol (CBD)
Ginger
C
D
Echinacea
C Black cohosh C Beta-sitosterol D Red rice yeast
D D
Garlic
Fenugreek
X
Wheat grass/ Barley grass
D Aloe
X
*Being phased out as of June 30, 2015. Note. Adapted from “Lexicomp Online for Dentistry,” by Wolters Kluwer, n.d., retrieved from http://webstore.lexi.com/ONLINE-Software-for- Dentists; and “About Natural Medicines Comprehensive Database,” by the Natural Medicines Comprehensive Database, n.d.a, retrieved from http:// naturaldatabase.therapeuticresearch.com/Content.aspx?cs=&s=ND&page= aboutdbhtml&xsl=generic#ratings Any drug or chemical substance administered to the mother is capable of crossing the placenta to some extent unless it is destroyed or altered during passage or its molecular size and low lipid solubility limit transplacental transfer (Illsley, Hall, Penfold, & Stacey, 1985). Substances of low molecular weight (<600 daltons) diffuse freely across the placenta, driven primarily by the concentration gradient (Kraemer, 1997; Zhang, Xia, Yan, & Liu, 2015). Conclusion Recognition and avoidance of potential herbal-drug interactions with commonly prescribed medications in dentistry will help OHCPs to optimize patient treatment while emphasizing patient safety. Based on the half-life of many of these agents, simply asking the patient to stop taking the herbal medication at least 24 hours before the dental appointment will prevent many potential interactions. Although medications that are commonly Resources Helpful websites and literature to enhance further learning: Websites ● The American Herbalists Guild (AHG) contributes to the evolution of herbalism in our country and in the
world. Their vision is that all herbalists, regardless of their affiliation or nonaffiliation with the AHG, will work together as peers toward this end. website : http://www.americanherbalistsguild.com
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