5 nausea meds and descriptions

Nausea

An unpleasant subjective sensation that stimulates the vomiting center in the brain stem.

Vomiting center (VC) stimulation

Can be stimulated directly (inflammation, hypoxia, GI distension) or indirectly (vestibular input, emotions, CTZ stimulation).

Chemoreceptor Trigger Zone (CTZ) stimulation causes

Uremic toxins, acidosis, pregnancy, toxins.

Receptors involved in nausea and vomiting

Opiate, histamine, serotonin, substance P receptors.

General management approaches for nausea

Patient care and comfort, hydration, and medication.

Ondansetron (Zofran) mechanism of action

Inhibits serotonin at receptor sites in vagal nerve terminals and in the CTZ.

Average dose and form of Ondansetron

PO and IV forms; 4-8 mg.

Patient care considerations for Ondansetron

Well tolerated, can cause headache/constipation. Risks: serotonin syndrome, QT prolongation, Stevens-Johnson syndrome.

Promethazine (Phenergan) mechanism of action

Blocks histamine, alters dopamine effects in CNS, inhibits CTZ, has anticholinergic properties.

Average dose and form of Promethazine

PO, PR, IV forms; 6.25-50 mg.

Patient care considerations for Promethazine

Causes sedation, possible respiratory depression (esp. elderly). IV infiltration can cause necrosis—dilute in 9 mL NS and push slowly ≥2 min. Monitor respiratory status.

Corticosteroids (e.g., Dexamethasone) role

Mechanism unclear; may boost effect of other meds.

Patient care considerations for Corticosteroids

Mood changes, insomnia, fluid retention, ↑BP, muscle weakness, impaired wound healing, infection risk, monitor blood sugar.

Dopamine antagonists (e.g., Metoclopramide) mechanism of action

Inhibits input into the vomiting center and promotes gastric emptying.

Patient care considerations for Dopamine antagonists

Contraindicated in bowel obstruction. Risk of tardive dyskinesia, pseudo-parkinsonism, restlessness/akathisia.

NK-1 inhibitors (e.g., Aprepitant) mechanism of action

Inhibits input of substance P into the vomiting center.

Patient care considerations for NK-1 inhibitors

Used prophylactically (e.g., before chemo), not effective once vomiting. May cause fatigue, reduces birth control effectiveness, not for pregnancy. Dangerous with pimozide.

Cannabinoids (e.g., Dronabinol) mechanism of action

Complex CNS effects, mimics SNS activity.

Patient care considerations for Cannabinoids

Increase appetite, decrease nausea. May worsen mania, depression, schizophrenia. Caution in cardiac disease/seizures. Can impair abilities, paradoxical vomiting, habit forming, avoid in pregnancy.

Benzodiazepines (e.g., Lorazepam) mechanism of action

Reduce anxiety, sedation, and possible depression of the vomiting center.

Patient care considerations for Benzodiazepines

Sedation and respiratory depression possible. No driving, avoid alcohol/CNS depressants. Risk of dependence; taper to prevent withdrawal.

Anticholinergics (e.g., Scopolamine) mechanism of action

Reduce vestibular input to the CTZ.

Patient care considerations for Anticholinergics

Patch behind ear. Effects: drowsiness, dry mouth, urinary retention, dilated pupils, blurred vision, agitation/confusion. Avoid alcohol/CNS depressants. Teach dry mouth remedies. Report toxicity.

Signs of Anticholinergic toxicity

Drowsiness, dizziness, dry mouth, urinary retention, dilated pupils, blurred vision, agitation, confusion.