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Dr. Jo
Dr. Jo, Veterinarian
Category: Veterinary
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Experience:  DVM from Iowa State University in 1994; actively engaged in private regular and emergency practice since that time.
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I have a 12 year old lab mix that has vomited some blood. He

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I have a 12 year old lab mix that has vomited some blood. He has lost weight over past 12 months. He has occasional appetite. Not wanting any heroics but want him comfortable. Looking for advice to possibly assist if he has ulcer or possibly tumor to make his comfortable. I'm a medical professional with DEA license.
JA: I'm sorry to hear that. What sort of animal are we talking about?
Customer: 12 year old lab mix.
JA: Maybe I'm confused. I thought you had a problem with a pet. Is that correct?
Customer: Yes. My dog.
JA: This sounds like it might be serious. I'll let the Veterinarian know what's going on ASAP. Is there anything else the Veterinarian should be aware of about your dog?
Customer: No melena. Think all Upper GI

I'm Dr. Jo and I'm a licensed veterinarian with more than twenty years of experience. I'm here to help with your question about your dog. I'm so sorry you are having this problem, but glad you're looking for the information you need. You may join the conversation at any time by typing in what you want to say then clicking REPLY or SEND. Then we can chat back and forth until you're satisfied with the information I've provided. I'll do my best to earn your good rating, because that's the only way I receive any compensation for helping you.In the meantime, in order to help me help you better, I'll need some more information. To start with, can you please tell me:

  • How long has he been vomiting?
  • Has he had his kidney enzymes checked recently? I ask because kidney disease is the most common thing to cause intermittent appetite issues, gradual weight loss, and some vomiting in an older pet.

I'll be standing by and awaiting your reply. Thank you.

Customer: replied 8 months ago.
About a week ago noticed it. Then he felt better. Vomited this am with small amount clotted blood. No melena. No recent labs.

Was the clotted blood in the vomit this morning bright red or dark brown/black, please?

Customer: replied 8 months ago.
Mixture. His vomit last week seemed more frank blood

Okay... that helps to know, and makes it more likely the bleeding was the result of the retching action, and less likely to be associated with an ulcer.

(typing more)

Customer: replied 8 months ago.
Ok. I am leaving country tomorrow and want to know what otc might help? Zantac?

I want to start by saying I completely understand where you're coming from with not wanting to pursue heroics. I understand your goal is to be compassionate and ensure his comfort for as long as possible.

With that in mind, the best advice I can give is to make an effort to determine the cause of all these symptoms (the gradual weight loss, vomiting, and appetite issues) for sure. Then you'll know exactly what you're up against and can make a good, informed choice regarding treatment.

Because these symptoms can be caused by a wide variety of problems, symptomatic treatment is not a wise choice. For a problem that's been going on this long and only getting worse, you need a diagnosis.

Therefore, the best advice I can give for how to help your dog be more comfortable is to have him seen by a veterinarian. You don't have to pursue any heroics at all, but a full physical examination and basic blood and urine tests are in order. With that simple workup you'll be at the very least pointed in the right direction, if not given your complete diagnosis. Then you'll know what will help.

H2 antagonists like Pepcid are used as ancillary therapy in most problems that cause these symptoms, but are unlikely to be of much benefit as sole therapy.
Regardless, I can get you dosing information. One moment ...

Customer: replied 8 months ago.
Ok. Thanks

So you have the complete information, here's the monograph on ranitidine (Zantac)

Ranitidine HCl

  • (rah-nit-a-deen)
  • Zantac®
  • H2 Receptor Antagonist; Prokinetic

Prescriber Highlights

  • H2 receptor antagonist similar to cimetidine, but fewer drug interactions; used to reduce acid output in stomach; also has prokinetic activity.
  • Contraindications: Hypersensitivity. Caution: Geriatric patients, hepatic or renal insufficiency.
  • Adverse Effects: Rare. IV boluses may cause vomiting. Potentially: Mental confusion, agranulocytosis, & transient cardiac arrhythmias (too rapid IV injection). Pain at the injection site after IM administration.


In veterinary medicine, ranitidine has been used for the treatment and/or prophylaxis of gastric, abomasal and duodenal ulcers, uremic gastritis, stress-related or drug-induced erosive gastritis, esophagitis, duodenal gastric reflux and esophageal reflux. One study did not demonstrate any reduction in the incidence of gastroesophageal reflux in anesthetized dogs from either ranitidine or metoclopramide (Favarato et al. 2012). Ranitidine has also been employed to treat hypersecretory conditions associated with gastrinomas and systemic mastocytosis. Because of its effects on gastric motility, ranitidine may be useful in increasing gastric emptying, particularly when delayed gastric emptying is associated with gastric ulcer disease. Ranitidine may also be useful to stimulate colonic activity in cats via its prokinetic effects.


At the H2 receptors of the parietal cells, ranitidine competitively inhibits histamine, thereby reducing gastric acid output both during basal conditions and when stimulated by food, amino acids, pentagastrin, histamine, or insulin. Ranitidine is between 3-13X more potent (on a molar basis) as cimetidine.

Ranitidine may stimulate GI motility, especially in the stomach by inhibiting acetylcholinesterase (thereby increasing acetylcholine at muscarinic receptors). Lower esophageal sphincter pressures may be increased by ranitidine. By decreasing the amount of gastric juice produced, ranitidine decreases the amount of pepsin secreted.

Ranitidine, unlike cimetidine, does not appear to have any appreciable effect on serum prolactin levels, although it may inhibit the release of vasopressin.


In dogs, the oral bioavailability is approximately 81%, serum half-life is 2.2 hours and volume of distribution is 2.6 L/kg.

In horses, oral ranitidine has a bioavailability of ≈ 27% in adults and 38% in foals. Peak levels after oral dosing occur in ≈ 100 minutes in adults and 60 minutes in foals. Apparent volume of distribution is ≈ 1.1 L/kg and 1.5 L/kg in adults and foals, respectively. Clearance in adults is ≈ 10 mL/min/kg and 13.3 mL/min/kg in foals.

In humans, ranitidine is absorbed rapidly after oral administration, but undergoes extensive first-pass metabolism with a net systemic bioavailability of approximately 50%. Peak levels occur at ≈ 2-3 hours after oral dosing. Food does not appreciably alter the extent of absorption or the peak serum levels attained.

Ranitidine is distributed widely throughout the body and is only 10-19% bound to plasma proteins. Ranitidine is distributed into human milk at levels 25-100% of those found in plasma.

Ranitidine is both excreted in the urine by the kidneys (via glomerular filtration and tubular secretion) and metabolized in the liver to inactive metabolites; accumulation of the drug can occur in patients with renal insufficiency. The serum half-life of ranitidine in humans averages 2-3 hours. The duration of action at usual doses is from 8-12 hours.


Ranitidine is contraindicated in patients who are hypersensitive to it. It should be used cautiously and possibly at reduced dosage in patients with diminished renal function. Ranitidine has caused increased serum ALT levels in humans receiving high IV doses for longer than 5 days. The manufacturer recommends that with high-dose chronic therapy, serum ALT values be considered for monitoring.

Adverse Effects

Adverse effects appear to be very rare in animals at the dosages generally used. Potential adverse effects (documented in humans) that might be seen include mental confusion and headache. Rarely, agranulocytosis may develop and, if given rapidly IV, transient cardiac arrhythmias may be seen. Pain at the injection site may be noted after IM administration. IV boluses have been associated with vomiting in small animals and transient hypotension in cats.

Reproductive/Nursing Safety

In humans, the FDA categorizes this drug as category B for use during pregnancy (Animal studies have not yet demonstrated risk to the fetus, but there are no adequate studies in pregnant women; or animal studies have shown an adverse effect, but adequate studies in pregnant women have not demonstrated a risk to the fetus in the first trimester of pregnancy, and there is no evidence of risk in later trimesters.) In a separate system evaluating the safety of drugs in canine and feline pregnancy (Papich 1989), this drug is categorized as class: B (Safe for use if used cautiously. Studies in laboratory animals may have uncovered some risk, but these drugs appear to be safe in dogs and cats or these drugs are safe if they are not administered when the animal is near term.)

Ranitidine is excreted in human breast milk with milk:plasma ratios of approximately 5:1 to 12:1. The drug is not recommended to be used in nursing humans; use with caution in nursing veterinary patients.

Overdosage/Acute Toxicity

Clinical experience with ranitidine overdosage is limited. In laboratory animals, very high dosages (225 mg/kg/day) have been associated with muscular tremors, vomiting and rapid respirations. Single doses of 1 gram/kg in rodents did not cause death.

Treatment of overdoses in animals should be handled using standard protocols for oral ingestions of drugs; clinical signs may be treated symptomatically and supportively if necessary. Hemodialysis and peritoneal dialysis have been noted to remove ranitidine from the body.

Drug Interactions

Unlike cimetidine, ranitidine appears to have much less effect on the hepatic metabolism of drugs and is unlikely to cause clinically relevant drug interactions via this mechanism. The following drug interactions have either been reported or are theoretical in humans or animals receiving ranitidine and may be of significance in veterinary patients. Unless otherwise noted, use together is not necessarily contraindicated, but weigh the potential risks and perform additional monitoring when appropriate.

  • Acetaminophen: Ranitidine (dose-dependent) may inhibit acetaminophen metabolism.
  • Antacids (high doses): May decrease the absorption of ranitidine; give at separate times (2 hours apart) if used concurrently.
  • Ketoconazole, Itraconazole: Absorption may be reduced secondary to increased gastric pH.
  • Metoprolol: Ranitidine may increase metoprolol half-life, and peak levels.
  • Nifedipine: Ranitidine may increase nifedipine AUC by 30%.
  • Probenecid: May reduce the excretion of ranitidine.
  • Propantheline: Delays the absorption but increases the peak serum level of ranitidine; relative bioavailability of ranitidine may be increased by 23% when propantheline is administered concomitantly with ranitidine.
  • Vitamin b-12: Long-term ranitidine use may reduce oral absorption of B-12.

Laboratory Considerations

  • Ranitidine may cause a false-positive urine protein reading when using Multistix®. The sulfosalicylic acid reagent is recommended for determining urine protein when the patient is concomitantly receiving ranitidine.



  • For esophagitis, ulcer disease, gastritis, or gastric prokinetic (extra-label): Common anecdotal dosages generally range from 1 – 2 mg/kg PO, SC, IM or slow IV q8-12h, but one study (Bersenas et al. 2005) found that ranitidine at 2 mg/kg IV q12h did not significantly increase gastric pH when compared to saline. One source (Spillman 2012) states: “Therefore, current dose recommendations (0.5 – 2 mg/kg q8–12h) seem to be too low to be of any effect. Currently, clinical studies on the effect of ranitidine on gastric disorders in dogs and cats are lacking.”


  • For ulcer disease, esophagitis, or as a prokinetic agent to stimulate colonic motility (extra-label): Based on pharmacokinetic data: 2.5 mg/kg slow IV twice daily or 3.5 mg/kg PO twice daily. (Trepanier 2010)


  • For Helicobacter mustelae (extra-label): Ranitidine bismuth citrate (Note: Not available commercially in USA; must be compounded) at 24 mg/kg PO q8-12h and clarithromycin (12.5 mg/kg PO q8-12h). Treat with both for 14 days. (Johnson-Delaney 2008)

Horses: (Note: ARCI UCGFS Class 5 Drug)

  • As a gastroprotectant/reduce stomach acid (extra-label): 1.5 – 2 mg/kg IV q8h or 6.6 – 10 mg/kg PO q8h.

Small Mammals:

  • Rabbits: As a prokinetic: 0.5 mg/kg IV q24 with cisapride (0.5 mg/kg PO q8h) (Lichtenberger 2008). For suspected gastric ulceration: 2 – 5 mg/kg PO twice daily. (Bryan 2009)


  • Clinical efficacy (dependent on reason for use); monitored by decrease in clinical signs, endoscopic examination, blood in feces, etc.

Client Information

  • Used to treat or prevent stomach ulcers.
  • Works best if given before the first meal of the day.
  • Ranitidine is available OTC (over the counter; without a prescription), but only give it to your animal if your veterinarian recommends.


An H2 receptor antagonist, ranitidine HCl occurs as a white to pale-yellow granular substance with a bitter taste and a sulfur-like odor. The drug has pKas of 8.2 and 2.7. One gram is soluble in approximately 1.5 mL of water or 6 mL of alcohol. The commercially available injection has a pH of 6.7-7.3.

Ranitidine HCl may also be known as: AH-19065, ranitidini hydrochloridum. Many trade names are available; a common trade name is Zantac®.


Ranitidine tablets should be stored in tight, light-resistant containers at room temperature. The injectable product should be stored protected from light and at a temperature less than 30°C. A slight darkening of the injectable solution does not affect the potency of the drug.

Compatibility/Compounding Considerations

Ranitidine injection is reportedly stable up to 48 hours when mixed with the commonly used IV solutions (including 5% sodium bicarbonate).

Dosage Forms/Regulatory Status

Veterinary-Labeled Products: None.

The ARCI (Racing Commissioners International) has designated this drug as a class 5 substance. See the appendix for more information.

Human-Labeled Products:

Ranitidine HCl Oral Tablets: 75 mg, 150 mg & 300 mg; Zantac®, generic; (Rx or OTC)

Ranitidine HCl Oral Solution: 15 mg/mL in 473 mL & 480 mL; generic; (Rx)

Ranitidine HCl Injection: 25 mg/mL; Zantac®, generic; (Rx)


Monograph revised/updated August 2014.

Bersenas, A., et al. (2005). Effects of ranitidine, famotidine, pantoprazole, and omeprazole on intragastric pH in dogs. AJVR 66(3): 425-31.

Bryan, J. (2009). Rabbit GI Physiology: What do I do now? Proceedings: WVC. accessed via Veterinary Information Network;

Favarato, E. S., et al. (2012). Evaluation of metoclopramide and ranitidine on the prevention of gastroesophageal reflux episodes in anesthetized dogs. Research in Veterinary Science 93(1): 466-7.

Johnson-Delaney, C. (2008). Gastrointestinal Diseases in Ferrets. Proceedings: WVC. accessed via Veterinary Information Network;

Lichtenberger, M. (2008). What's new in small mammal critical care. Proceedings: AAV. accessed via Veterinary Information Network;

Papich, M. (1989). Effects of drugs on pregnancy. Current Veterinary Therapy X: Small Animal Practice. R. Kirk. Philadelphia, Saunders: 1291-9.

Spillman, T. (2012). Antiemetics and Gastroprotective Drugs in Dogs: Fact and Fiction. Proceedings: WSAVA/FECAVA/BSAVA World Congress 2012. accessed via Veterinary Information Network;

Trepanier, L. (2010). Acute Vomiting in Cats: Rational treatment selection. Journal of Feline Medicine and Surgery 12(3): 225-30.

I'll break it down here, though. ...

"For dogs:

  • For esophagitis, ulcer disease, gastritis, or gastric prokinetic (extra-label): Common anecdotal dosages generally range from 1 – 2 mg/kg PO, SC, IM or slow IV q8-12h, but one study (Bersenas et al. 2005) found that ranitidine at 2 mg/kg IV q12h did not significantly increase gastric pH when compared to saline. One source (Spillman 2012) states: “Therefore, current dose recommendations (0.5 – 2 mg/kg q8–12h) seem to be too low to be of any effect. Currently, clinical studies on the effect of ranitidine on gastric disorders in dogs and cats are lacking.”

So, as you can see, we often reach for drugs like this to provide relief for dogs with GI signs, but expectations for any effectiveness should be kept very low.

I wish there was something OTC that would be more helpful for you, but at least now you know there isn't.

Is there anything else I can help you with today? I want to be as helpful as possible because I know what it's like to be stuck in a situation like this and be worried.

Customer: replied 8 months ago.
Anything from pharmacy more helpful? I can write an rx if something more effective.

Unfortunately, no.

The problem here isn't what pill he needs. In order to provide any real relief, we need to know what we're treating. That means the quickest route to effective relief for him is in pursuit of a diagnosis. Most clinics can get you same-day results on a basic blood panel and urinalysis.

Customer: replied 8 months ago.
Ok. Thanks. My vet can't get him in today and not fan of our emergency vet. They don't seem to understand palliative care. Thanks for your help.

I understand your frustrations. I know it can be hard, and you need a good vet you can trust in somewhat of a hurry.

My apologies, however, if I've been misunderstanding things from the get-go.

I'm a huge advocate of palliative care and compassion with end-of-life issues. What I haven't seen in your description of your situation so far is that we know you're in a palliative care situation. Did I miss somewhere your statement that you already know your dog has a terminal diagnosis? I'm so sorry if I overlooked that reading in a hurry as I do. Please explain again...

Are you still there?

I'm just trying to do my best to understand your situation and be helpful.

Customer: replied 8 months ago.
Sorry. Sitting in a Advanced Cardiac Life Support class.With his age and gradual weight loss my assumption is some sort of malignancy.

Not necessarily. While it's realistic to prepare yourself for the worst, there are also some good options on the differential list.

!2 isn't all that old for a lab; some make it upwards of 15. This could be something as simple as a thyroid or adrenal issue, or.... heck... even worms.

Customer: replied 8 months ago.
Ok. Going to make appointment and have my housesitter take him in to my normal vet. Thanks.

Good plan. Let's be hopeful it's something simple.

Customer: replied 8 months ago.

I hope this information was helpful to you. I've done my best to provide accurate and thorough information for your situation..

Please also remember I am here for you and am happy to discuss your question until you are satisfied with the answer I've provided. You may return to this page at any time to review this information and/or post more. You may do so even after you've rated my response. I'll be notified of your response via email and will do my best to help you.Thank you for using our website.
Dr. Jo and 3 other Veterinary Specialists are ready to help you

Just checking in to ask how things are going with your dog. Did you get a diagnosis yet?

Thank you,

Dr. Jo