Antiemetics, Antispasmodics & Laxatives Flashcards
Antiemetics
4
- Anticholinergics
- Antihistamines
- Dopamine receptor antagonists
Phenothiazines
Benzamides - Serotonin antagonists
WHat are the Dopamine receptor antagonists? 2
- Phenothiazines
2. Benzamides
Neurotransmitter receptor sites involved in the vomiting reflex?
5
- M1 – muscarinic
- D2 – dopamine
- H1 – histamine
- 5-hydroxytryptamine (HT)-3
- -serotonin - Neurokinin 1 (NK1) receptor
- -substance P
Anticholinergic agents
- Acts on what receptors?
- Main drug in this category?
- Predominantly used for what?
- Administered how?
- SE? 3
- M1 – muscarinic receptor
- Scopolamine is the main drug in this category
- Predominantly used as prophylaxis against motion sickness
- Delivered transdermally, 1.5 mg every 72 hours
- Side effects include
- dry mouth,
- drowsiness
- vision disturbance
Antihistamines:
- MOA?
- Primary use is for?
- What are the drugs?
- Common side effect?
- H1 blockers
- Primary use is for motion sickness
- Diphenhydramine (Benadryl)
- Cylizine (Cyclivert)
- Dimenhydrinate (Dramamine)
- Meclizine (Dramamine-Less Drowsy)
- Sedation is a common side effect along with anticholinergic effects
Dopamine Receptor Antagonists
- What are the phenothiazines?2
- What are the benzamides? 2
- Phenothiazines
- Prochlorperazine (Compazine)
- Promethazine (Phenergan) - Benzamides
- Metachlopramide (Reglan)
- Trimethobenzamide (Tigan)
Phenothiazines
- Work on what receptor sites? 3
- Commonly used as what line of agent?
- Administration? 3
- Have antagonistic properties at D2, H1 and M1 sites
- Commonly used as first line agents
- Oral, rectal or IV
Main adverse effects of the phenothiazines
5
- Extrapyramidal reactions such as dystonia
- -Compazine has higher incidence of EPS than Phenergan - Tardive dyskinesia with prolonged use
- Acute dystonia can be treated with diphenhydramine 25 to 50 mg IV or IM
- Hypotension can also occur, particularly in the elderly or with intravenous infusion
- Sedation, drowsiness, anticholinergic effects (dry mouth, urinary retention, blurred vision)
Precautions with phenothiazines?
4
Use with caution in
- elderly,
- with other CNS depressants,
- poorly controlled seizures,
- severe liver dysfunction
Benzamides: Metachlopramide (Reglan) 1. MOA at low doses? 2. MOA at high doses? 3. How does it act on gastric smooth muscle? Neuromuscular junction?
Metachlopramide (Reglan)
- Central and peripheral dopamine D2 antagonism at low doses
- Weak 5-HT3 blockade at the higher doses
- Stimulates cholinergic receptors on gastric smooth muscle cells and enhances acetylcholine release at the neuromuscular junction
Benzamides:
Trimethobenzamide (Tigan)
1. Mechanism of action is unclear but works centrally in the area of the what?
- Is generally considered the most potent antiemetic that does not have effects on the serotonergic, dopaminergic, or histaminergic systems, so it has a lower likelihood of causing what?
- medulla oblongata
2. undesired side effects
Serotonin 5-HT3 Antagonists
1. Potent antiemetic properties mediated mainly through what?
central 5-HT3-receptor blockade in vomiting center AND chemoreceptor trigger zone blockade of 5-HT3 receptors
Serotonin 5-HT3 Antagonists Clinical Uses
3
- Great for postoperative and chemotherapy induced nausea and vomiting
- Can be used for most cases of nausea and vomiting except not great for nausea secondary to vestibular system etiology (vertigo)
–Usually effective as single agents
5-HT3 Receptor Antagonists
- Most common adverse effects include?
- Examples? 4
- Headache,
- dizziness, and
- constipation
2.
- Ondansetron (Zofran) **Most popular
- Granisetron (Kytril)
- Dolasetron (Anzemet)
- Palonosetron (Aloxi)
- Most commonly used 5HT-3 Receptor Antagonist is what?
- Approved use for who? 2
- Preg cat?
- Drug interactions? 3
2. Odansetron (Zofran) Approved for use in children and adults Pregnancy cat B Drug interactions: -caution for serotonin syndrome, -QT prolongation, -monitor liver function tests if prolonged use
What are the ways to administer zofran?4
- Solution (Zofran Injection)
40 mg/20 mL (20 mL): $256.40
2. Tablet, orally-disintegrating (Ondansetron Oral) 4 mg (30): $668.78 8 mg (30): $1113.95
3. Tablet, orally-disintegrating (Zofran ODT Oral) 4 mg (30): $752.17 8 mg (30): $1252.86
4. Tablets (Ondansetron HCl Oral) 4 mg (30): $735.05 8 mg (30): $1217.42
Differential diagnosis of nausea/vomiting
6
- Medications, toxicities
- Infections (GI, ear)
- Gut disorders
- CNS causes
- Endocrine
- Misc.
- Post operative, cardiac, radiation, etc.
Nausea and vomiting associated with chemotherapy is treated differently (_____________ is a helpful adjunct)
Dexamethasone
Antibiotics for Treatment of Infectious Diarrhea: Empiric Antibiotic Therapy? 2
- Oral Fluoroquinolone:
- Ciprofloxacin 500 mg PO twice daily,
- Norfloxacin 400 mg PO twice daily, or
- Levofloxacin 500 mg PO once daily (all for 3-5 days) - Oral Macrolides:
- Azithromycin 500 mg PO once daily for 3 days or
- Erythromycin 500 mg PO twice daily for 5 days (especially if fluoroquinolone resistance is suspected)
When would you reccommend pharmacologic therapy for the symptomatic treatment of diarrhea? 2
What would we use?
- NO fever
- NO blood in stool
Then can use an antimotility agent to decrease the number of stools per day
- Bismuth subsalicylate (Pepto-Bismol) can be used for treatemant of what?
- Considered what kind of drug?
- MOA?
- traveler’s diarrhea
- Considered an absorbant
- MOA: may exert its antidiarrheal action not only by stimulating absorption of fluid and electrolytes across the intestinal wall but also, when hydrolyzed to salicylic acid, by inhibiting synthesis of a prostaglandin responsible for intestinal inflammation and hypermotility.