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Nausea and Vomiting in Pregnancy
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9. Are these medications harmful to my fetus?
The agents below are Pregnancy Class A – C. (see Table, page bottom). None of the above medications have been associated with an increased risk of fetal malformations.
See Drug
Safety below. Also see these drugs in pregnancy databases Teris
or Reprotox
See also Lifestyle and Natural Agents
Agent |
Drug Class |
Dosage |
FDA Class |
Rx |
|---|---|---|---|---|
Pyridoxine (Vitamin B6) |
Vitamin B6 |
25 mg po |
A |
Oral: 10-25 mg po tid Most prenatal vitamins contain 2-10 mg Vit B6 |
Doxylamine |
Antihistamine (H-1 Blocker) |
12.5 mg po |
A |
Oral: 12.5 mg po tid (½ of 25 mg) 3-4 x / day NB: Some OTC preps contain diphenhydramine |
Fructose, dextrose, and orthophosphoric acid * |
Antiemetic |
15-30 mL |
A |
Oral: 15-30 mL on arising; repeat every 3 hours or when nausea threatens |
Doxylamine / pyridoxine* Available in Canada, not available in U.S.* |
Antihistamine (H-1 Blocker)
|
Doxylamine succinate 10 mg po / pyridoxine hydrochloride 10 mg po |
A |
Oral: Two delayed release tablets (a total of doxylamine 20 mg and pyridoxine 20 mg) at bedtime. In severe cases or in cases with nausea/vomiting during the day, dosage may be increased by 1 tablet in the morning and/or afternoon. |
Promethazine |
Antihistamine |
12.5-25 mg po |
C |
Oral, I.M., I.V., rectal: 12.5-25 mg every 4-6 hours as needed |
Hydroxyzine* |
Antihistamine |
12.5-25 mg po |
C |
Oral: 12.5-100 mg/dose every 4-6 hours as needed |
Dimenhydrinate* |
Antihistamine |
50-100 mg 50 mg IV |
B |
Oral: 50-100 mg every 4-6 hours, (not to exceed 400 mg/day or 200 mg/day if on doxylamine) I.V. 50 mg in 50 mL NS q4-6h IV over 20 minutes |
Metoclopramide |
Cholinomimetic |
5-10 mg po |
B |
Oral: 10-15 mg/dose up to 4 times/day 30 minutes before meals or food and at bedtime. Single doses of 20 mg are occasionally needed for provoking situations I.V.: 5-10 mg q8h IV (5-10 mg/kg) |
Dolasetron |
Selective 5-HT3 Receptor Antagonist |
25-100 mg po 4-8 mg IV |
B |
Oral: 25-200 mg single dose
(0.6-5 mg/kg as a single dose |
*Over the counter names available on request
Drug Safety
A number of reports have demonstrated that antiemetic drug therapy is effective
and does not increase the incidence of
congenital anomalies.
Some examples are illustrated below:
The safety of antihistamines was affirmed in a meta-analysis that examined the association between antihistamine use and major malformations. This review of 24 controlled studies including over 200,000 first trimester exposures found that H1-receptor blockers actually had a protective effect (odds ratio 0.76, 95 percent CI 0.60 to 0.94). Pooled analysis also demonstrated efficacy of this class of drugs (RR 0.34, 95 percent CI 0.27 to 0.43).
The original formulation of Bendictin ® contained the anticholinergic doxycyclomine, which was removed due to lack of efficacy. It has been estimated that when the combination doxycyclomine / B6 was available from 1958 – 1983 25-30% of all pregnant patients received this agent. A meta-analysis of studies on outcome of pregnancies exposed to Bendectin ® reported no increase in the incidence of birth defects. Pooled analysis demonstrated efficacy of Bendectin ® (RR 0.53, 95 percent CI 0.41 to 0.68). In addition, data from a Swedish registry on women who took promethazine or meclizine in the first trimester did not show an increase in the rate of birth defects. In fact, withdrawal was associated with a two-fold increase in the admission rate to hospitals in Canada with subsequent decline correlating with rising rates of their OTC doxycyclomine / B6 preparation.
Evidence from systematic review (n = 2948 exposed patients) showed that dopamine antagonists (eg, phenothiazines, droperidol, metoclopramide) were not teratogenic (RR 1.03, 95 percent CI 0.88 to 1.22)]. The best studied drugs in this class are the phenothiazines, which appeared effective (RR 0.31, 95 percent CI 0.24 to 0.42).
Ondansetron is the most widely used HT3 antagonist largely due to its effectiveness in chemotherapy-induced emesis. Animal data are reassuring as to safety in pregnancy, but human data on safety or efficacy are sparse. In contrast, no published reports on dolasetron in human pregnancy have been found. Based on ondansetron’s published human experience and a lack of embryo / fetal toxicity in two animal species with dolasetron, it represents minimal, if any risk to the human fetus.
CATEGORY | INTERPRETATION* |
|---|---|
A |
Adequate, well-controlled studies in pregnant women have not shown an increased risk of fetal abnormalities to the fetus in any trimester of pregnancy. |
B |
Animal studies have revealed no evidence of harm to the fetus,
however, there are no adequate and well-controlled studies in pregnant women. |
C |
Animal studies have shown an adverse effect and there are
no adequate and well-controlled studies in pregnant women. |
D |
Adequate well-controlled or observational studies in pregnant women have demonstrated a risk to the fetus. However, the benefits of therapy 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. |
X |
Adequate well-controlled or observational studies in animals or pregnant women have demonstrated positive evidence of fetal abnormalities or risks. The use of the product is contraindicated in women who are or may become pregnant. |
http://www.perinatology.com/exposures/Drugs/FDACategories.htm
FDA Consumer magazine Volume 35, Number 3 May-June 2001
