Agent	Dosage	Adverse effects	Notes
Primary therapies
Vitamin B6	10 to 25 mg every eight hours	Paresthesias, headache, fatigue	First-line therapy
Doxylamine (Unisom SleepTabs)	12.5 to 25 mg every eight hours	Drowsiness	May use lower dose in the morning and at midday, and larger dose at night
Secondary therapies
Dimenhydrinate	50 to 100 mg every four to six hours	Drowsiness, dizziness, headache, fatigue	—
Diphenhydramine (Benadryl)	25 to 50 mg every eight hours	Drowsiness, dizziness, headache, fatigue	—
Hydroxyzine (Vistaril)	50 mg every four to six hours	Drowsiness, dizziness, headache, fatigue	—
Meclizine (Antivert)	25 mg every six hours	Drowsiness, dizziness, headache, fatigue	—
Metoclopramide (Reglan)	10 mg every six hours	Tardive dyskinesia	Avoid high dosages or treatment for longer than 12 weeks
Ondansetron (Zofran)	4 to 8 mg every six hours	Headache, diarrhea, constipation, fatigue	Available as oral disintegrating tablet
Promethazine	12.5 to 25 mg every four to six hours	Sedation, extrapyramidal symptoms	Avoid intravenous administration (associated with tissue damage); oral, rectal, or intramuscular administration is safer; can be compounded as transdermal gel
Therapies for refractory nausea and vomiting
Droperidol	1.25 to 2.5 mg intramuscularly or intravenously	Torsades de pointes, prolonged QT interval	—
Methylprednisolone	16 mg every eight hours for three days, then taper over two weeks	—	Increased risk of cleft lip if used before 10 weeks' gestation; data on effectiveness are mixed; may be given orally or intravenously
Prochlorperazine	5 to 10 mg every six hours	Sedation, extrapyramidal symptoms, hypotension	Available as buccal tablet
Scopolamine	1-mg patch behind ear every three days	Drowsiness, dry mouth, urinary retention	May cause limb and trunk deformities if used in first trimester
Trimethobenzamide (Tigan)	300 mg every six to eight hours	Sedation, anticholinergic effects	—