If nonpharmacological measures fail, then administer antiemetic medication.
There are two groups of antiemetics: nonprescription and prescription. Nonpre-
scription antiemetics are purchased over-the-counter and used to prevent motion
sickness. They have little effect controlling severe vomiting. They must be taken
30 minutes before traveling and are not effective once vomiting occurs.
Antihistamine antiemetics such as diphenhydrinate (Dramamine), meclizine
hydrochloride (Antivert), and diphenhydramine hydrochloride (Benadryl) are
over-the-counter medications that prevent nausea, vomiting, and dizziness (ver-
tigo) caused by motion by inhibiting stimulation in the middle ear. They also
cause drowsiness, dryness of the mouth, and constipation.
Several over-the-counter drugs—such as bismuth subsalicylate (Pepto-
Bismol)—act directly on the gastric mucosa to suppress vomiting. Such drugs
can be taken for gastric discomfort or diarrhea. Do not give Pepto-Bismol to
children who are vomiting who might be at risk for Reyes syndrome as it con-
tains salicylates.
Phosphorated carbodydrate solution (Emetrol), a hyperosmolar carbohydrate
is also available over-the-counter. It decreases nausea and vomiting by changing
the gastric pH or by decreasing smooth muscle contractions of the stomach. This
drug has a high sugar content and should not be used by diabetics.
Prescription antiemetics act as antagonists to dopamine, histamine, serotonin,
and acetylcholine. Antihistamines and anticholinergics act on the vomiting cen-
ter and decrease stimulation of the CTZ and vestibular pathways.
There are eight classifications of prescription antiemetics.ANTIEMETICS
Antihistamines
Antihistamines are used to decrease nausea and vomiting that occur after surgery.
They are also used for the management of motion sickness and to treat allergic
symptoms. Examples are Vistaril, Atarax, and Phenergan.
See antihistamines in the Appendix. Detailed tables show doses, recommen-
dations, expectations, side effects, contraindications, and more; available on the
book’s Web site (see URL in Appendix).Anticholinergics
Anticholinergics are used to prevent and treat nausea, vomiting and motion sick-
ness. They are also used to treat vertigo that is associated with vestibular system
disease. Scopolamine is an example of an anticholinergic agent.(^332) CHAPTER 18 Gastrointestinal System