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Veterinary Gastrointestinal Drugs
Veterinary gastrointestinal (GI) drugs treat a range of digestive disorders, including vomiting, diarrhea, constipation, and ulcers, in various animals. These medications are typically grouped by their function within the digestive system.
Common Types of Veterinary GI Drugs
Veterinarians use a variety of drug classes to address specific GI conditions:
Antiemetics
These drugs control nausea and vomiting by blocking signals to the brain’s vomiting center.
- Maropitant (Cerenia®): An FDA-approved medication for dogs and cats that blocks the neurotransmitter substance P, effective for motion sickness, chemotherapy side effects, and various GI issues.
- Ondansetron (Zofran®) & Dolasetron (Anzemet®): Serotonin antagonists used for severe vomiting, particularly during chemotherapy.
- Metoclopramide (Reglan®): Blocks dopamine receptors in the brain and also acts as a prokinetic, speeding up gastric emptying.
- Antihistamines: Dimenhydrinate (Dramamine®) and diphenhydramine (Benadryl®) are used for nausea caused by motion sickness.
Antiulcer and Acid Reducers
These medications reduce stomach acid secretion or protect the stomach lining to treat ulcers and acid reflux.
- Proton Pump Inhibitors (PPIs): Omeprazole (Prilosec®) and Pantoprazole are potent acid reducers, superior to H2 blockers for treating ulcers in many cases.
- H2 Receptor Antagonists: Famotidine (Pepcid®), Ranitidine, and Cimetidine block histamine receptors on parietal cells, decreasing acid production.
- Sucralfate: A cytoprotective agent that forms a sticky, protective barrier over ulcerated areas of the stomach and intestines, allowing the tissue to heal.
Motility Modifiers (Prokinetics)
These drugs stimulate and coordinate normal muscle contractions in the GI tract, helping food move through the digestive system.
- Metoclopramide (Reglan): Also listed under antiemetics, it increases gastric contractions and speeds the emptying of the stomach.
- Cisapride: A potent prokinetic with broader activity, useful for managing gastric stasis, idiopathic constipation, and megacolon in cats.
- Nizatidine: An H2 blocker that also has motility-stimulating effects through its anticholinesterase activity.
Antidiarrheals
These medications help manage diarrhea by slowing intestinal motility or absorbing excess water and toxins.
- Loperamide: Can be prescribed under strict veterinary guidance to slow bowel movements.
- Kaolin/Pectin: Common veterinary-approved ingredients that absorb toxins and firm stools.
Other Important GI Treatments
- Probiotics: Dietary supplements containing beneficial bacteria (e.g., FortiFlora) to restore healthy gut flora disrupted by illness or antibiotics.
- Antibiotics: Metronidazole, Tylosin, or other antibiotics may be used when bacterial infections (e.g., Salmonella, Clostridium) are confirmed or strongly suspected.
- Anthelmintics (Dewormers): Medications targeting internal parasites like roundworms and hookworms, which are a common cause of GI distress.
- Anti-inflammatories/Immunosuppressants: Medications such as prednisone or sulfasalazine are used to treat inflammatory bowel disease (IBD).
Veterinary Antiemitic Drugs
Ondansetron as a Veterinary Antiemetic Drug
Ondansetron (Zofran) is a powerful, off-label antiemetic used in veterinary medicine for severe nausea and vomiting in dogs and cats, especially when standard treatments fail or for conditions like chemo-induced sickness, parvovirus, or vestibular disease, working by blocking serotonin receptors (5-HT3) and available orally or via injection, with dosing and form determined by the veterinarian.
How it works
- It’s a 5-HT3 receptor antagonist, meaning it blocks serotonin from triggering vomiting signals in the brain and gut.
Common Uses in Veterinary Medicine
- Severe Vomiting: For cases unresponsive to other antiemetics.
- Chemotherapy: To prevent nausea and vomiting.
- Parvovirus: Effective for vomiting associated with this infection.
- Vestibular Disease: Helps control nausea from inner ear balance issues.
- Premedication: Before anesthesia to prevent post-operative nausea.
- Cats: Used for chronic kidney disease-related nausea.
Forms & Administration
- Oral: Tablets (regular or dissolving), liquid. Can be given with or without food; give with food if it causes vomiting on an empty stomach.
- Injectable: IV, IM, or subcutaneous in a hospital setting.
- Topical: A compounded gel form might be available, requiring gloves for application.
Dosing & Efficacy
- Dosage varies by species, size, and condition (e.g., ~0.11 mg/lb every 8-12 hrs for cats).
- It acts quickly, often within 1-2 hours, improving clinical signs.
- Studies show it reduces nausea signs like lethargy, lip-licking, restlessness, and vomiting.
Important Considerations
- Off-Label Use: It’s FDA-approved for humans, but vets use it legally off-label for animals.
- Follow Vet Instructions: Always follow your veterinarian’s specific directions carefully.
- Side Effects: May include diarrhea, constipation, or sedation.
Brand Names of Ondansetron in Veterinary in Bangladesh
In Bangladesh, ondansetron is not typically marketed under specific brand names designated solely for veterinary use. Instead, veterinarians often use human-grade ondansetron products in an “off-label” capacity. The brand names available in Bangladesh are manufactured by various pharmaceutical companies for human use.
Common brand names of ondansetron available in Bangladesh include:
- Ofran from Square Pharmaceuticals PLC.
- Onaseron from Incepta Pharmaceuticals
- Periset from ACME Laboratories Ltd.
- Novatron from Radiant Pharmaceuticals Ltd.
- Anset from Opsonin Pharma Ltd.
- Ondan from UniMed UniHealth Pharmaceuticals Ltd.
These products are available in various forms, such as tablets, oral solutions, and injections, and are prescribed by veterinarians for the treatment of severe nausea and vomiting in pets.
Metoclopramide as a Veterinary Antiemetic Drug
Metoclopramide is a widely used veterinary antiemetic and gastroprokinetic drug for dogs, cats, and other small mammals. It is a human-approved prescription medication used in an extra-label (off-label) manner in animals to control vomiting and stimulate upper gastrointestinal motility.
Mechanism of Action
Metoclopramide works through a dual mechanism:
- Central Antiemetic Effect: It acts as a dopamine (D2) receptor antagonist in the chemoreceptor trigger zone (CTZ) of the brain, blocking signals that cause nausea and vomiting.
- Prokinetic Effect: It stimulates motility in the stomach and upper small intestine by increasing acetylcholine release, which speeds gastric emptying and reduces esophageal reflux.
Uses in Veterinary Medicine
Veterinarians commonly prescribe metoclopramide for various conditions:
- Treatment or prevention of vomiting caused by metabolic diseases (e.g., kidney failure), gastrointestinal inflammation (gastroenteritis), or chemotherapy.
- Management of gastroesophageal reflux disease (GERD).
- Management of gastric motility disorders, such as gastroparesis or postoperative ileus.
- In some cases, to induce milk let-down and promote milk production in lactating animals.
Administration
Metoclopramide is available as tablets, oral syrup, and an injectable solution. It can be administered orally (preferably 15-30 minutes before meals), subcutaneously, intramuscularly, or via a constant rate intravenous infusion (CRI), especially for severe cases of vomiting.
Side Effects and Contraindications
Side effects are generally uncommon but can include neurological signs because the drug can cross the blood-brain barrier.
- Side Effects: Drowsiness, lethargy, motor restlessness, hyperactivity (especially in cats), or disorientation may occur. These signs usually resolve once the medication is stopped, and can sometimes be managed with diphenhydramine.
- Contraindications: Metoclopramide should not be used in animals with gastrointestinal obstruction, perforation, or hemorrhage, as its prokinetic effects could cause harm. It should also be avoided in animals with a history of seizures or pheochromocytoma (an adrenal gland tumor).
Comparison with Other Antiemetics
While metoclopramide is effective, other antiemetics like maropitant (Cerenia®) and ondansetron (Zofran®) are often more potent and are considered superior broad-spectrum options for many types of vomiting. Studies have shown that metoclopramide may be less effective as a central antiemetic in cats compared to dogs, due to neuroreceptor differences.
Brand Name of Metoclopramide in Veterinary in Bangladesh
In Bangladesh, metoclopramide is available under several brand names, and while there are no brand names specifically exclusive for veterinary use, the human versions are commonly prescribed by veterinarians.
Common brand names of metoclopramide available in Bangladesh include:
- Maxocol (manufactured by Medimet Pharmaceuticals Ltd.)
- Meclid (manufactured by Jayson Pharmaceutical Ltd.)
- Metocol (manufactured by Opsonin Pharma Ltd.)
- Motilon (manufactured by Synovia Pharma PLC)
- Nutramid (manufactured by ACME Laboratories Ltd.)
- Ultramet (manufactured by Ultra Pharma Ltd)
Veterinarians in Bangladesh legally prescribe these human-labeled metoclopramide products for animals in what is known as “extra-label” or “off-label” use. You can consult the Bangladesh National Veterinary Formulary for more comprehensive information on generally prescribed veterinary drugs in the country.
Diphenhydramine as a Veterinary Antiemetic Drug
Diphenhydramine (e.g., brand name Benadryl® or Vetadryl®) is commonly used in veterinary medicine for its antiemetic (anti-vomiting) effects, particularly in cases of motion sickness. Its efficacy is primarily due to blocking histamine (H1) receptors in the brain’s chemoreceptor trigger zone (CRTZ) and vestibular apparatus.
Mechanism of Action
Diphenhydramine is a first-generation antihistamine that readily crosses the blood-brain barrier. It works as an antiemetic by:
- Blocking H1 receptors: It competes with histamine for H1 receptors on cells in the CRTZ and the vestibular apparatus. The vestibular system is the main pathway for motion sickness-induced vomiting in dogs.
- Anticholinergic effects: It also has anticholinergic (muscarinic receptor antagonist) properties, which contribute to its antiemetic and sedative effects.
Usage and Efficacy
- Motion Sickness: Diphenhydramine is frequently used to prevent motion sickness in dogs, where H1 receptors play a significant role in the emetic response. It should be administered 30 to 60 minutes before travel for best results.
- Limitations: It is less effective for other causes of vomiting (e.g., kidney disease, chemotherapy) and is generally considered ineffective for motion sickness in cats. For many types of vomiting, veterinarians may choose more potent and specific antiemetics, such as maropitant (Cerenia®).
- Off-label Use: Its use as an antiemetic in small animals is often considered an “off-label” or “extra-label” use of the human drug, requiring explicit veterinary guidance.
Dosage and Administration
Dosage varies by species and condition, and should always be determined by a veterinarian. A common oral dosage for dogs is 2-4 mg per kg of body weight, two to three times daily. It is available in oral forms (tablets, liquids) and injectable forms (IV/IM/SC).
Side Effects and Precautions
The most common side effect is sedation (drowsiness). Other potential side effects include:
- Dry mouth
- Urinary retention
- Diarrhea
- Decreased appetite
Diphenhydramine should be used with caution in animals with glaucoma, severe heart failure, hyperthyroidism, or urinary/gastrointestinal obstructions. Overdose can cause central nervous system stimulation (excitement, seizures) or severe depression (lethargy, coma). It should not be used with other central nervous system depressants or anticholinergic drugs without veterinary supervision.
Brand Name of Diphenhydramine in Veterinary in Bangladesh
The primary brand name for Diphenhydramine in veterinary use in Bangladesh is Phenadryl Vet. It is manufactured by ACME Laboratories Ltd..
Phenadryl Vet is available in various formulations:
- Tablets/Bolus: 500 mg strength.
- Injection: 20 mg/ml concentration (for IV/IM use).
This medication is used to treat a range of conditions in large and small animals, including cutaneous allergies, urticaria, insect bites, and coughing.
While human formulations of diphenhydramine (e.g., as a syrup called Phenadryl) also exist in Bangladesh, the specific veterinary-labeled product is Phenadryl Vet. As with any veterinary medication, it should be used under the direction of a veterinary physician.
Veterinary Antiulcer and Acid Reducer Drugs
Proton Pump Inhibitors in Veterinary
Proton pump inhibitors (PPIs) are a class of drugs widely used in veterinary medicine, particularly in
dogs, cats, and horses, to treat conditions caused by excessive gastric acid secretion such as gastroduodenal ulcers and esophagitis. They are considered superior to other acid suppressants like H2 receptor antagonists for treating these conditions.
Common Proton Pump Inhibitors
The most common PPIs used in veterinary practice are human-approved formulations administered “off-label” (extra-label) for animals, with the exception of specific omeprazole products for horses.
- Omeprazole (brand names include Prilosec, Gastrogard) is the most widely used oral PPI.
- Pantoprazole (brand name Protonix) is often available in injectable forms for hospitalized patients who cannot take oral medications.
- Esomeprazole (brand name Nexium) is also used, sometimes found to be a superior acid suppressant in cats compared to others.
- Lansoprazole and dexlansoprazole are less commonly used or less effective in some species, such as cats.
Mechanism of Action
PPIs work by irreversibly blocking the H
+,K
+-ATPase proton pump located in the gastric parietal cells, which is the final step in acid production. They are administered in an inactive form and become activated in the acidic environment of the stomach, where they bind to and deactivate the pumps. Acid secretion only resumes when new proton pumps are synthesized, resulting in a prolonged effect, often lasting for several days after a single dose in some species.
For maximal effectiveness, PPIs should generally be given on an empty stomach, about 30-60 minutes before the first meal of the day, to target actively pumping parietal cells.
Clinical Uses
PPIs are the first-line therapy for several conditions in veterinary medicine:
- Treatment and prevention of gastric and duodenal ulcers and erosions (GUE).
- Management of gastroesophageal reflux disease (GERD) and erosive esophagitis.
- Prophylaxis against ulcers in animals with specific risk factors, such as mast cell tumors or gastrinomas which cause hyperacidity.
- Adjunct therapy for Helicobacter infections in dogs.
Inappropriate use of PPIs is common in veterinary hospitals, such as for the routine management of pancreatitis or renal disease without evidence of GI bleeding, which is not supported by current evidence-based guidelines.
Potential Adverse Effects and Considerations
While generally considered safe for short-term use, long-term administration of PPIs has been associated with potential adverse effects and drug interactions in both humans and animals:
- Gastrointestinal upset: The most common side effects are mild and include vomiting, decreased appetite, gas, and diarrhea.
- Intestinal dysbiosis: Altering stomach pH can change the balance of gut bacteria, potentially increasing the risk of certain infections (like Clostridium difficile) or exacerbating NSAID-induced intestinal damage.
- Nutrient absorption: Long-term use may interfere with the absorption of certain nutrients and other medications that require an acidic environment (e.g., some antifungals, iron, clopidogrel).
- Rebound acid hypersecretion: Abrupt discontinuation after prolonged use (more than 3-4 weeks) can lead to a temporary increase in acid production, so tapering the dose is often recommended.
