Treatment for vomiting

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Here is a comprehensive overview of the treatment of vomiting, organized by drug class and clinical context:

Treatment of Vomiting (Antiemetic Therapy)

1. Histamine (H₁) Antagonists

Drug	Dose	Main Use	Side Effects
Dimenhydrinate	50 mg orally q4–6h	Motion sickness, labyrinthine disorders, PONV	Sedation, dry mouth
Meclizine	25 mg orally daily	Motion sickness	Sedation
Promethazine	25 mg orally/suppository q4–6h	Motion sickness, PONV, gastroparesis	Sedation
Diphenhydramine	25 mg orally up to 2×/day	Gastroparesis, intestinal pseudo-obstruction	Sedation

These are particularly useful for vomiting due to vestibular/labyrinthine activation (e.g., motion sickness, labyrinthitis).

2. Muscarinic Antagonists

Drug	Dose	Main Use	Side Effects
Scopolamine	1.5 mg transdermal patch q72h	Motion sickness, PONV	Blurred vision, dry mouth/eyes, urinary retention, impaired concentration

3. Dopamine Antagonists

Drug	Dose	Main Use	Side Effects
Prochlorperazine	5 mg orally 3×/day	Gastroenteritis, toxins, PONV, CINV	Dystonia, tardive dyskinesia, galactorrhea, mood disturbances
Trimethobenzamide	300 mg orally 3×/day	Gastroenteritis, PONV	Dystonias
Metoclopramide	5 mg orally 3×/day (before meals)	Gastroparesis (also prokinetic)	Extrapyramidal effects, anxiety, mood disturbances

4. Serotonin (5-HT₃) Antagonists

Drug	Dose	Main Use	Side Effects
Ondansetron	4 mg orally 3×/day or 4–8 mg IV	CINV, PONV, HIV-related	Constipation, headache, cardiac arrhythmias
Granisetron	1 mg orally twice daily; or transdermal weekly patch	CINV, radiotherapy-induced	Constipation, fatigue
Dolasetron	50 mg orally once	CINV, PONV	Constipation
Palonosetron	0.25 mg IV once	CINV	Constipation, headache

These are first-line for chemotherapy-induced nausea and vomiting (CINV) and postoperative nausea and vomiting (PONV).

5. Neurokinin (NK₁) Receptor Antagonists

Drug	Dose	Main Use	Side Effects
Aprepitant	40–80 mg prior to chemotherapy or surgery	CINV, PONV	Anorexia, fatigue, somnolence, diarrhea/constipation

Used in combination regimens for highly emetogenic chemotherapy.

6. Corticosteroids

Drug	Dose	Main Use	Side Effects
Dexamethasone	4–5 mg IV prior to chemotherapy or surgery	CINV, PONV	Somnolence, weight gain

Often combined with ondansetron ± aprepitant for CINV.

7. Benzodiazepines

Drug	Dose	Main Use	Side Effects
Lorazepam	1 mg IV prior to chemotherapy	Anticipatory emesis	Sedation

Useful for the anticipatory (conditioned) component of chemotherapy-induced vomiting.

8. Cannabinoids

Drug	Dose	Main Use	Side Effects
Dronabinol	2.5 mg orally twice daily	CINV (refractory)	Anxiety, depression, hyperglycemia, hypertension

9. Herbal/Non-Pharmacological

Ginger 1 g orally daily — general indications including motion sickness, morning sickness, CINV (side effect: heartburn)
STW5 20 drops in water 3×/day before meals

Special Clinical Situations

Nausea & vomiting in pregnancy / Hyperemesis gravidarum:

First-line: Pyridoxine (Vitamin B6) 10 mg + Doxylamine 10 mg — FDA-approved, fetal safety well-documented
If admission required: IV crystalloids for rehydration + Ondansetron 4 mg IV q8h
Thiamine 100 mg IV to prevent Wernicke encephalopathy in severe/prolonged cases
Phenothiazines (metoclopramide, prochlorperazine, promethazine) are commonly used in pregnancy; bulk of evidence does not show increased congenital anomaly risk

PONV (Postoperative): Ondansetron ± dexamethasone; scopolamine patch; droperidol

CINV (Chemotherapy-induced):

Highly emetogenic: 5-HT₃ antagonist + NK₁ antagonist (aprepitant) + dexamethasone ± lorazepam
Breakthrough CINV: Benzodiazepines (e.g., lorazepam) or additional antiemetics

Gastroparesis: Metoclopramide (prokinetic + antiemetic); antihistamines; ondansetron

Motion sickness: Scopolamine patch, dimenhydrinate, meclizine

Sources: Yamada's Textbook of Gastroenterology (Table 33.2), Goldman-Cecil Medicine, Rosen's Emergency Medicine, Katzung's Basic and Clinical Pharmacology

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