Nausea and Vomiting
GENERAL PRINCIPLES
Nausea and vomiting may result from side effects of medications, systemic illnesses, central nervous system (CNS) disorders, and primary GI disorders.
Vbmiting that occurs during or immediately after a meal can result from acute pyloric stenosis (e.g., pyloric channel ulcer) or from functional disorders, while vomiting within 30-60 minutes after a meal may suggest gastric or duodenal pathology.
Delayed vomiting of undigested food from a previous meal can suggest gastric outlet obstruction or gastroparesis. Symptoms of gastroparesis may be indistinguishable from functional dyspepsia and chronic functional nausea and vomiting with normal gastric emptying.35
DIAGNOSIS
Bowel obstruction and pregnancy should be ruled out.
Medication lists should be carefully scrutinized for potential offenders, and systemic illnesses (acute and chronic) should be evaluated as etiologies or contributing factors.
Endoscopy and/or imaging should be considered in the setting of nonresolving or red flag symptoms, such as hematemesis or weight loss.
TREATMENT
Correction of fluid and electrolyte imbalances is an important supportive measure.
Oral intake should be limited to clear liquids, if tolerated. Many patients with self-limited illnesses require no further therapy.
NG decompression may be required for patients with bowel obstruction or protracted nausea and vomiting of any etiology.
Enteral feeding through jejunal tubes or, rarely, total parenteral nutrition (TPN) may be necessary to supplement nutrient intake.
Medications
Empiric pharmacotherapy (Table 18-2) is often initiated while investigation is in progress or when the etiology is thought to be self-limited.
TABLE 18-2
COMMONLY USED ANTIEMETICS
| Medication | Dosage | Receptor Target | Comments |
| Diphenhydramine 25-50 mg PO q6h 10-50 mg IV q6h | Histamine (Hi) | May cause sedation | |
| Dimenhydrinate | 50-100 mg PO q4h | Histamine (H1) | May cause sedation |
| Meclizine | 25-50 mg PO q4h | Histamine (H1) | Often used for motion-sickness; may cause sedation |
| Promethazine | 12.5-25 mg PO, IM or PR q4-6h | Histamine (H1) | Drowsiness, dystonic reactions; risk of extrapyramidal symptoms |
| Scopolamine | 1.5 mg q72h transdermal | Muscarinic (M1) | May cause dry mouth, drowsiness |
| Prochlorperazine | 5-10 mg PO qid 2.5-10 mg IV q4h. Maxdose 40 mg/d | Dopamine (D2) | Prolongs QT |
| Haloperidola | 0.5-2 mg PO or IV q6-8h | Dopamine (D2) | Prolongs QT; risk of extrapyramidal symptoms including acute dystonia |
| Metoclopramide | 10 mg PO or IV q6h | Dopamine (D2) Serotonin (5-HT3) | Risk of extrapyramidal symptoms; not recommended for long-term use |
| Ondansetron | 4-8 mg PO or IV q8h | Serotonin (5-HT3) | Prolongs QT |
| Olanzapinea | 5-10 mg daily | Dopamine (D2) Serotonin (5-HT2) | Used for chemotherapy-induced nausea; prolongs QT, may cause sedation |
| Aprepitant | 125 mg PO prior to chemotherapy, 80 mg PO on days 2 and 3 | Neurokinin- 1 (NK1) | Used for chemotherapy-induced nausea; many drug-drug interactions |
| Lorazepama | 0.5-2 mg PO q6h | GABA-A | Does not prolong QT |
| Dexamethasonea | 4-8 mg IV once | Mechanism unclear | Used for chemotherapy-induced nausea; may cause insomnia, mood changes |
aConsidered off-label use.
Phenothiazines and related agents: Prochlorperazine and promethazine are often used as first-line agents in nausea. Drowsiness is a common side effect, and acute dystonic reactions or other extrapyramidal effects may occur.
Dopamine antagonists: Metoclopramide is a prokinetic agent with central antiemetic effects.
Drowsiness and extrapyramidal reactions may occur, and a warning has been issued by the US Food and Drug Administration (FDA) regarding the risk of permanent tardive dyskinesia with high-dose and/or long-term use.36 Tachyphylaxis may limit long-term efficacy. Domperidone is an alternate agent that does not cross the blood-brain barrier and therefore has no CNS side effects; however, it is not uniformly available. Antihistaminic agents: Diphenhydramine, dimenhydrinate, and meclizine are most useful for nausea and vomiting related to motion sickness but may also be useful for other causes.
Serotonin 5-hydroxytryptamine-3 (5-HT3) receptor antagonists: Ondansetron is effective in chemotherapy-associated emesis. It can also be used in emesis that is refractory to other medications, especially the sublingual formulation.
Neurokinin-1 (NK-1) receptor antagonist: Aprepitant is an alternative agent intended for chemotherapy-induced nausea and vomiting.
Lorazepam, haloperidol, and olanzapine are other medications with antiemetic effect.
More on the topic Nausea and Vomiting:
- Nausea and Vomiting
- Diabetic Neuropathy
- Weight loss and anorexia
- HEADACHE
- Pain
- Chronic Obstructive Pulmonary Disease
- Head Trauma
- 14 Hypoadrenocorticism in a dog
- Sources of Marine Pollution
- Inflammatory Bowel Disease