Antiemetic agent

Action

Dosage

Side effects

Anticholinergics/

antimuscarinics

A direct depressant action on the VC.

An antispasmodic action on the gut.

Useful for motion sickness and post-operative N/V (PONV)

Hyoscine (scopolamine) SC, IV, IM 0.3–0.6 mg q4–8 h prn

Glycopyrolate 1–2 mg q8–12 h. Useful with colicky N/V associated with mechanical bowel obstruction

‘Central cholinergic syndrome’ (confusion, disorientation, visual hallucinations) may occur in the elderly

Pupil dilation, blurred vision, drowsiness, urinary retention, and dry mouth

Antihistamines

Antagonize the action of histamine at the H₁ receptor

Useful for treating nausea associated with motion sickness, mechanical bowel obstruction, or ↑ ICP

Meclizine 25–50 mg 3–4 times/day

Diphenhydramine 25–50 mg PO 3–4 times/day

Hydroxyzine 25 mg PO, IV 3–4 times/day

Drowsiness, blurred vision, confusion

Butrophenones/

Phenothiazines

Dopamine (D₂) antagonists act primarily in the CTZ.

First-line agents for most types of end-of-life N/V

Droperidol IV, IM: 2.5–5 mg q3–4 h

Haloperidol 0.5–5 mg q4–6 h prn or routinely. Ceiling dose at 30 mg/day

Prochlorperazine IV, IM, PR, or PO: 5–20 mg q4–6 h prn or routinely (slow onset of action at 2–4 h after peak plasma concentrations) can go as high as 1–2 mg/kg with increased risk of restlessness, sedation, and dry mouth. Effective in PONV

Clorpromazine IV, PR 25–50 mg q6–12 h. Also effective for hiccups

Promethazine (H₁-receptor antagonist)—avoid use due to excessive sedation and minimal efficacy

Sedation, hypotension, anticholinergic effects, and EPS (dystonia and akathesia)

May prolong QT interval, provoking ventricular arrhythmias (more so with Droperidol)

dexamethasone adds to efficacy of haloperidol and metoclopramide.

Dronabinol adds to procholoperzine’s efficacy for chemo induced N/V.

Give metoclopramide with haloperidol only if haloperidol is a low dose and EPS s/e are not present

Steroids

Action not clear; May involve ↓ serotonin turnover in the CNS and mediate the cerebral cortex pathway to the VC Considered second line and can be adjuvant as mentioned above

Will stimulate appetite and reduce somatic and visceral pain

Dexamethasone IV and PO: 0.5–8 mg q6–12 h

Euphoria, insomnia, hyperglycemia, HTN, and immunosuppression in long-term use

Used as a prophylactic agent for acute and delayed nausea d/t chemotherapy

Synergistic with serotonin antagonists, metoclpramide, and phenothiazines

Hormone,

anti-diarrheal

Globally decreases GI secretions. Effective in refractory nausea, first line for bowel obstruction

Octreotide(Sandostatin®)—Must be given as an SQ injection 3 times/day. 50–100 mcg q8 × 48 h or 10 mcg/h continuous infusion SC or IV

Minimal

Neuroleptic,

Atypical neuroleptic

Quetiapine 25 mg PO BID and titrate

Olanzapine: 2.5 mg PO QD. May advance to 5–10 mg QD.

Perphenazine : 8–16 mg PO 2–4 times/day (ceiling dose: 64 mg/day; 24 mg in ambulatory patients)

Dizziness, hypotension, hyperkinesia, somnolence, nausea

Benzodiazepines

Amnesic and anxiolytic activity at the GABA receptors found in the cerebral cortex

Not to be used as a single agent for N/V

Most effective for anticipatory N/V associated with chemotherapy, abdominal radiotherapy, and other noxious treatments

Midazolam Inj: 1,5 mg/ml q3 hours prn or 0.5–5.0 mg/h sc continuous infusion