Nausea and Vomiting Flashcards
what is the pathophysiology of nausea and vomitng
* the chemoreceptor trigger zone receives most of the impulses from drugs, toxins and the vestibular center
* the neurotransmitter dopamine stimulates the chemoreceptor trigger zone, which stimulates the vomiting center when triggered, motor neuron responds–> contraction of diaphragm, anterior abdominal muscles & stomach. The glottis closes, the abdominal wall moves upward and vomiting occurs
good hx and PE is key to management
Forceful expulsion of gastric contents through involuntary muscular contractions
Vomiting
food returning to the mouth w/o forceful contractions
regurgitation
food returned to the mouth through voluntary contractions
rumination
- Class: Benzamide
- MOA: prokinetic, increases peristalsis in upper gut, acts as central and peripheral D2-receptor antagonists (low doses). Weak serotonin-receptor blocker (high doses)
- indications: N&V from gut stasis. Ineffective in post operative nausea & vomiting
- ADR: readily cross BBB, so extrapyramidal effects, restlessness, depression (especially in older patients), sedation. Avoid in GI tract obstruction
Metoclopramide
- Delayed gastric emptying in the absence of a mechanical obstuction
- sxs: early satiety, bloating, N/V, anorexia, abd. Pain, weight loss
- Causes: DM, gastic surg, pseudo-obstruction, GI infection, anorexia nerv. (1/3 idopathic (viral damage to myenteric plexus of the gastic smooth muscles); diabetic (nerve damage to DM)
- DX: H&P, endoscopy, barium swallow, gastric emptyings, and gastoduodenal manometry
Gastroparesis
Treatment of gastroparesis
- reverse/correct underlying etiology and promote gastic emptying
- modifications like reducing solid foods, smaller more frequent meals, low in fiber and fat (these inhibit gastric emptying)
- prokinetic therapy: metoclopramide, erythromycin
- anti-emetics- metoclopramide, promethazine
- endoscopic decompressive gastromy
- Class: 5-HT3 receptor antagonist
- MOA: Blocks 5-HT3 receptors at the CTZ and in the GI tract. oral and IV safe efficacy and onset of action. Antiemetic action due to effect on abdominal vagal afferent nerve. Also has a CNS effect
- cytotoxic chemo agents increase serotonin release in SB, activating 5HT3 receptors on vagal abdominal afferents
- indications: N&V related to chemotherapy, radiotherapy and surgery. Now the cornerstone for actue emesis
- ADRs: Headace & constipation, hiccups, avoid if concomitant drug that prolongs QT
Ondansetron
- Class: Phenothiazine (1st group active against chemo-induced emesis)
- MOA: Acts on the central (postrema/CTZ) dopamine D2-receptor antagonist. Also muscarinic M1 and histamine H1-receptor blocking activity
- indications: moderately effective in nausea due to various GI disorders. Mildly effective in chemo induced emesis. Also used in vertigo, motion sickness, migrane and PONV
- ADR: extrapyramidal reactions, gangrene, resp. depression confusion, sedation, hyptention
Promethazine
what medication is Anti SLUDGE? what does that mean?
Promethazine
- decreased salvation, lacrimation, urination, defecation, gastritis, emesis
- Class: Butyrophenones
- MOA: D-2 receptor dopamine antagonist. Blocks the action of acetylcholine, improving N &V
- others: droperidol (Significant improvement)
- indications: N&V, from chemical or drug causes. Commonly used in palliative care. Works great for opioid induced nausea
- superior the phenothiazines as they bind differently to dopamine receptors
- ADR: extrapyramidal effects, tardive dyskinesia w/ chronic use, sedation. ADRs
Best for opioid induced nausea and vomiting
Haloperidol
- Class: Anticholenergic
- MOA: muscarinic M1- receptor antagonist (modest efficacy, W/ poor tolerance)
- indications: prophylaxis against motion sickness
- ADRs: dry mouth, drowsiness, visual disturbances
- Antiemetic
Hyoscine (Scopolamine)
- Class: Antihistamine
- MOA: H1 receptor antagonist
- indications: best if given before onset of N&V. Used mostly for motion sickness, vertigo and migraine
- ADRs: Dry mouth and blurred vision. May potentiate other CNS sedatives
Meclizine
- Cannabinoids
- MOA: THC as antiemetic, unknown mechanism
- indications: modest effects in PCNV
- ADRs: Anxiety, euphoria, sedation, paranoia, GERD
- adding to antiemetic boosts efficacy by 20%
Marijuana
what are other methods of treating nausea and vomiting in pregnancy?
- Ginger
- sea bands
- vitamin b6 (greater reduction in nausea from baseline, compared to placebo. No difference in reported vomiting)
- hyperemesis gravidarum–> promethazine is a good start but drowsiness ADR
- ondansetron: avoid in 1st trimester- teratogenic
