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Dr. Jo
Dr. Jo, Dog Veterinarian
Category: Dog Veterinary
Satisfied Customers: 2477
Experience:  DVM from Iowa State University in 1994; actively engaged in private regular and emergency practice since that time.
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I accidently stepped on Daisy a cockapoo foot, shes limping

Customer Question

Hello Dr. Andy
I accidently stepped on Daisy a cockapoo foot, shes limping but does not seem in pain and can put very little weight on it. this happened Tues 2/9.
Not sure if its broken can I give her Tylenol or something else
Submitted: 10 months ago.
Category: Dog Veterinary
Expert:  Dr. Jo replied 10 months ago.

Hello,

I'm sorry Dr. Andy isn't currently available. I'm Dr. Jo and I'm here to help with your question about Daisy.

Expert:  Dr. Jo replied 10 months ago.

I'm so sorry you're 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.

So I may know we're properly connected and that you understand how the website works (including that I'll need to earn your good rating in order to receive any compensation for helping you), please type in a short response below. You may rest assured you'll have my full attention and will receive a complete response once I know you're there.

Expert:  Dr. Jo replied 10 months ago.

Please rest assured that accidents like this are quite common, and I know how upsetting it can be. While, on the one hand, Daisy doesn't seem painful, we have to acknowledge that her limping is the result of pain.

I'm sorry, I hate to be the bearer of bad news.

Most of the time when the injury is simple and uncomplicated, the foot heals up within 24 hours and by the next day you will see little to no limping. Since this has been two days and she's still limping, I'm worried.

I can see you're worried about her too; that's why you're here looking for information.

I'm also glad you're wondering what you can give her for pain.

The unfortunate reality of this situation is that it is not a good idea to give her ANY type of human drug for pain. The real solution to your problem lies in having her seen by a veterinarian so you can know the full extent of the injury. That includes having x-rays taken, if needed. Once you know why she is still limping two days later, then an appropriate treatment plan can be developed. That may involve casting, a splint, surgery, or just rest and pain medications. Your vet will be able to prescribe pain medications that are SAFE and EFFECTIVE for use in dogs.

To clarify, the human or over-the-counter pain medications that are available without a prescription are not likely to be either safe or effective. At best (like aspirin) they're not likely to provide any substantial relief without causing side effects. At worst, like with ibuprofen, the drug is toxic to dogs and can be lethal at even a relatively low dose.

So, from a point of view of what's best for Daisy, I would recommend taking her to the vet for a full exam and treatment.

For the sake of providing you with complete and accurate information, I will give you the dosing information for aspirin and tylenol below, but please remember neither drug tends to be very effective for dogs.

Expert:  Dr. Jo replied 10 months ago.

Here is the information for tylenol. As you can see, it's not a very safe or effective choice. I do not recommend using it.

Acetaminophen

  • (ah-seet-a-min-a-fen)
  • Tylenol®, APAP, Paracetamol
  • Oral Analgesic, Antipyretic

Prescriber Highlights

  • Contraindicated in cats at any dosage; ferrets may be as sensitive to acetaminophen as cats.
  • At recommended dosages, not overly toxic to dogs, rodents, or rabbits. Dogs are more susceptible to red blood cell toxicity than are humans, so dose carefully.
  • Often used in combined dosage forms with codeine, tramadol or hydrocodone; see the codeine, tramadol or hydrocodone monographs for more information.

Uses/Indications

Acetaminophen is occasionally used as an oral analgesic in dogs and small mammals. It may be particularly beneficial in dogs with renal dysfunction for the treatment of chronic pain conditions. In situations where moderate pain occurs, it may be used in combination products containing codeine, hydrocodone, or tramadol. See the codeine, hydrocodone and tramadol monographs for more information on the use of acetaminophen combination preparations.

A case report of adjunctive treatment for pain using oral acetaminophen in a pony has been published (West et al. 2011).

Pharmacology/Actions

Acetaminophen’s exact mechanisms of action are not completely understood; it produces analgesia and antipyresis via a weak, reversible, isoform-nonspecific inhibition of cyclooxygenase (COX-3; Cox-1-v1). Unlike aspirin, it does not possess significant antiinflammatory activity nor inhibit platelet function when given at clinically recommended dosages.

Pharmacokinetics

Acetaminophen’s pharmacokinetics have been evaluated after single oral doses (mean dose = 10.46 mg/kg) in 6 greyhounds (KuKanich 2010). Oral absorption is rapid and peak levels of about 6.8 mcg/mL occurred 51 minutes (mean) after a dose. Terminal half-life was also fast and was approximately 1 hour.

In humans, acetaminophen is rapidly and nearly completely absorbed from the gut and is rapidly distributed into most tissues. Approximately 25% is plasma protein bound.

Contraindications/Precautions/Warnings

Acetaminophen is contraindicated in cats at any dosage. Severe methemoglobinemia, hematuria, and icterus can be seen. Cats are unable to significantly glucuronidate acetaminophen leading to toxic metabolites being formed and resultant toxicity. Presently, acetaminophen should not be used in ferrets as in vitro studies indicate they may be as sensitive to acetaminophen as cats. At this time, acetaminophen should not be used in Sugar Gliders or Hedgehogs, as its safety has not been determined.

Dogs do not metabolize acetaminophen as well as humans and its use must be judicious. While dogs are not as sensitive to acetaminophen as cats, they may also be susceptible to methemoglobinemia when given high dosages. In dogs, it is generally not recommended to use acetaminophen during the immediate post-operative phase (first 24 hours) due to an increased risk of hepatotoxicity.

Adverse Effects

Because acetaminophen is not routinely used in veterinary medicine, experience on its adverse effect profile is limited. At suggested dosages in dogs, there is some potential for renal, hepatic, GI, and hematologic effects occurring. Higher dosages (3X) can cause keratoconjunctivitis sicca.

Reproductive/Nursing Safety

Absolute reproductive safety has not been established, but acetaminophen is apparently relatively safe for occasional use in pregnancy (no documented problems in humans). Animal data was not located. 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: C (These drugs may have potential risks. Studies in people or laboratory animals have uncovered risks, and these drugs should be used cautiously as a last resort when the benefit of therapy clearly outweighs the risks.)

Acetaminophen is excreted in milk in low concentrations with reported milk:plasma ratios of 0.91-1.42 at 1 and 12 hours, respectively. In nursing human infants, no adverse effects have been reported.

Overdosage/Acute Toxicity

Because of the potentially severe toxicity associated with acetaminophen, consultation with an animal poison control center is highly recommended (seeappendix). Effects can include methemoglobinemia, liver necrosis, renal effects, facial and paw swelling, and keratoconjunctivitis sicca (KCS). Liver effects are more common in dogs; facial and paw swelling and methemoglobinemia are more common in cats. Dosages above 100 mg/kg in dogs have been associated with severe toxicosis.

There were 6194 single agent exposures to acetaminophen only products reported to the ASPCA Animal Poison Control Center (APCC) during 2009-2013. Of the 5698 dogs exposed, 1206 were symptomatic. The common signs in the dogs included vomiting (31%), lethargy (24%), ataxia (8%), facial edema (5%), and 3% with elevated liver enzymes and/or methemoglobinemia. Of the 473 cats, 214 were symptomatic with 28% reporting vomiting, 21% hypersalivating, 15% lethargic, 9% tachypneic, 8% had methemoglobinemia, and 6% had elevated liver enzymes. For overdosage in dogs or cats, standard gut emptying techniques and supportive care should be administered when applicable. Further treatment with acetylcysteine, s-adenosyl methionine (SAMe), oxygen, and blood transfusions may be warranted (Richardson 2000), (Aronson et al. 1996), (Mariani et al. 2001), (Steenbergen 2003).

Drug Interactions

The following drug interactions with acetaminophen have either been reported or are theoretical in humans or animals 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.

  • Barbiturates: Increased conversion of acetaminophen to hepatotoxic metabolites; potentially increased risk for hepatotoxicity.
  • Doxorubicin: May deplete hepatic glutathione, thereby leading to increased hepatic toxicity.
  • Fenbendazole: May increase the risk for hepatotoxicity (study done in mice) (Gardner et al. 2012).
  • Isoniazid: Possible increased risk of hepatotoxicity.
  • Phenothiazines: Possible increased risk for hypothermia.
  • Propylene glycol: Foods containing propylene glycol (often found in wet cat foods) may increase the severity of acetaminophen-induced methemoglobinemia or Heinz body formation.
  • Warfarin: While acetaminophen is relatively safe to use, large doses may potentiate anticoagulant effects.

Laboratory Considerations

  • False positive results may occur for urinary 5-hydroxyindoleacetic acid.

Doses

Note: For dosages of acetaminophen/codeine, and acetaminophen/hydrocodone combination products refer to the codeine and hydrocodone monographs.

Dogs:

  • As an analgesic (extra-label): 10 – 15 mg/kg PO q8h; if using long-term (>5 days) consider giving q12h at the lower end of dosing range.

Rabbits/Rodents/Small Mammals:

  • As an analgesic (extra-label):
    1. Using Children’s Tylenol®: 1 – 2 mg/mL in drinking water. Effective for controlling low-grade nociception. (Huerkamp 2000)
    2. Mice, Rats, Gerbils, Hamsters, Guinea pigs, Chinchillas: 1 – 2 mg/mL in drinking water. (Adamcak et al. 2000)

Monitoring

  • When used at recommended doses for pain control in otherwise healthy patients, little monitoring should be necessary. However, with chronic therapy, occasional liver, renal and hematologic monitoring may be warranted, particularly when clinical signs occur.

Client Information

  • Must never be used in cats. Do not use in ferrets.
  • Not commonly used in dogs; watch for adverse effects and contact veterinarian if dog stops eating, if the whites of the eyes become yellowish, continues vomiting or having diarrhea, or blood is seen in vomit or stool.
  • Do not give more than veterinarian prescribes. Unless veterinarian instructs, do not give other pain or fever medicines.
  • Keep out of reach of children.

Chemistry/Synonyms

A synthetic non-opiate analgesic, acetaminophen (also known as paracetamol) occurs as a crystalline, white powder with a slightly bitter taste. It is soluble in boiling water and freely soluble in alcohol. Acetaminophen is known in the U.K. as paracetamol.

Acetaminophen may also be known as: paracetamol, N-acetyl-p-aminophenol, MAPAP or APAP; many trade names are available.

Storage/Stability

Acetaminophen products should be stored at temperatures less than 40°C. Do not freeze the oral solution or suspension.

Compatibility/Compounding Considerations

Non-extended release tablets may be split or crushed and mixed with food just prior to administration.

Dosage Forms/Regulatory Status

Veterinary-Labeled Products: None.

The ARCI (Racing Commissioners International) has designated this drug as a class 4 substance. See the appendix for more information.

Human-Labeled Products:

There are many different trade names and products of acetaminophen available commercially. The most commonly known trade name is Tylenol®.Acetaminophen is available in 160 mg, 325 mg and 500 mg tablets, capsules or caplets; 80 mg chewable tablets; 650 mg extended release tablets; oral liquids in several different concentrations and 80 mg, 120 mg, 125 mg, 300 mg, 325 mg and 650 mg rectal suppositories. Combinations with other analgesics (aspirin, codeine phosphate, hydrocodone, tramadol, or oxycodone) or antihistamines (diphenhydramine) are also available.

Revisions/References

Monograph revised/updated August 2013.

Adamcak, A. & B. Otten (2000). Rodent Therapeutics. Vet Clin NA: Exotic Anim Pract 3:1(Jan): 221-40.

Aronson, L. & K. J. Drobatz (1996). Acetaminophen Toxicosis in 17 Cats. Vet Emerg Crit Care 6: 65-9.

Gardner, C., et al. (2012). Exacerbation of acetaminophen hepatotoxicity by the anthelmentic drug fenbendazole. Toxicol Sci. 125(2): 607-12.

Huerkamp, M. (2000). The use of analgesics in rodents and rabbits. Emory University, Division of Animal Resources.

KuKanich, B. (2010). Pharmacokinetics of acetaminophen, codeine, and the codeine metabolites morphine and codeine-6-glucuronide in healthy Greyhound dogs. J. Vet. Pharmacol. Ther. 33(1): 15-21.

Mariani, C. & R. Fulton (2001). Atypical Reaction to Acetaminophen Intoxication in a Dog. Vet Emerg Crit Care 10: 123-6.

Richardson, J. (2000). Management of Acetaminophen and Ibuprofen Toxicosis in Dogs and Cats. Vet Emerg Crit Care 10: 285-91.

Steenbergen, V. (2003). Acetaminophen and Cats A Dangerous Combination. Vet Tech: 43-5.

West, E., et al. (2011). Use of acetaminophen (paracetamol) as a short-term adjunctive analgesic in a laminitic pony. Veterinary Anaesthesia and Analgesia 38: 521-2.

January 1, 2005 (published) | January 1, 2015 (revised)

Expert:  Dr. Jo replied 10 months ago.

And here is the information on aspirin. Again, it is pretty easy to see why I don't recommend it either.

Aspirin

  • (ass-pir-in)
  • ASA, Acetylsalicylic Acid
  • Analgesic; Antipyretic; Platelet Aggregation Reducer; Antiinflammatory

Prescriber Highlights

  • NSAID used for analgesic, antiinflammatory & antiplatelet effects in a variety of species.
  • Contraindicated in patients hypersensitive to it or with active GI bleeds; Relatively contraindicated in patients with bleeding disorders, asthma, or renal insufficiency (but has been used to treat glomerular disease).
  • Aspirin has a very long half-life in cats (approx. 30 hours; dose carefully); dogs are relatively sensitive to GI effects (bleeding).
  • Low grade teratogen & may delay labor; avoid use in pregnancy.
  • Many drug & lab interactions.

Uses/Indications

Aspirin is used for its analgesic, antipyretic, and antiplatelet effects.

Pharmacology/Actions

Aspirin inhibits cyclooxygenase (COX-1, prostaglandin synthetase) thereby reducing the synthesis of prostaglandins and thromboxanes (TXA2). These effects are thought to be how aspirin produces analgesia, antipyrexia, and reduces platelet aggregation and inflammation.

Most cells can synthesize new cyclooxygenase, but platelets cannot. Therefore, aspirin can cause an irreversible effect on platelet aggregation. A study in dogs investigating the platelet function effects of various aspirin doses, showed that doses <1 mg/kg/day or at 10 mg/kg/day PO did not have any statistically significant effect on platelet aggregation. Doses of 12 mg/kg/day inhibited platelet function and aggregation (Shearer et al. 2009).

Aspirin has been shown to decrease the clinical signs of experimentally induced anaphylaxis in calves and ponies.

While aspirin does not directly inhibit COX-2, it can modify it to produce, with lipoxygenase (LOX), a compound known as aspirin-triggered lipoxin (ATL), which appears to have gastric mucosal protective actions. This may explain why aspirin tends to have reduced gastric damaging effects when used over time.

Pharmacokinetics

Aspirin is rapidly absorbed from the stomach and proximal small intestine in monogastric animals. The rate of absorption is dependent upon factors as stomach content, gastric emptying times, tablet disintegration rates and gastric pH. In cattle, oral dosages of 50 mg/kg did not achieve therapeutic concentrations (Coetzee 2013).

During absorption, aspirin is partially hydrolyzed to salicylic acid where it is distributed widely throughout the body. Highest levels may be found in the liver, heart, lungs, renal cortex, and plasma. The amount of plasma protein binding is variable depending on species, serum salicylate and albumin concentrations. At lower salicylate concentrations it is 90% protein bound, but only 70% protein bound at higher concentrations. Salicylate is excreted into milk but levels appear to be very low. Salicylate will cross the placenta and fetal levels may actually exceed those found in the mother.

Salicylate is metabolized in the liver primarily by conjugation with glycine and glucuronic acid via glucuronyl transferase. Because cats are deficient in this enzymatic pathway, they have prolonged half-lives (27-45 hours) and are susceptible to accumulating the drug. Minor metabolites formed include gentisic acid, 2,3-dihydroxybenzoic acid, and 2,3,5-trihydroxybenzoic acid. Gentisic acid appears to be the only active metabolite, but because of its low concentrations appears to play an insignificant role therapeutically. The rate of metabolism is determined by both first order kinetics and dose-dependent kinetics depending on the metabolic pathway. Serum half-life in dogs is approximately 8 hours, in cats, approximately 38 hours, while in humans it averages 1.5 hours. Generally, steady-state serum levels will increase to levels higher (proportionally) than expected with dosage increases. These effects have not been well studied in domestic animals, however.

The kidneys rapidly excrete salicylate and its metabolites by both filtration and renal tubular secretion. Significant tubular reabsorption occurs which is highly pH dependent. Raising urine pH to 5-8 can significantly increase salicylate excretion. Salicylate and metabolites may be removed using peritoneal dialysis or more rapidly using hemodialysis.

Contraindications/Precautions/Warnings

Aspirin is contraindicated in patients demonstrating previous hypersensitivity reactions to it or with bleeding ulcers. It is relatively contraindicated in patients with hemorrhagic disorders, asthma, or renal insufficiency.

Because aspirin is highly protein bound to plasma albumin, patients with hypoalbuminemia may require lower dosages to prevent clinical signs of toxicity. Aspirin should be used cautiously with enhanced monitoring in patients with severe hepatic failure or diminished renal function. Because of its effects on platelets, aspirin therapy should be halted, if possible, one week prior to surgical procedures.

Aspirin must be used cautiously in cats because of their inability to rapidly metabolize and excrete salicylates. Clinical signs of toxicity may occur if dosed recklessly or without stringent monitoring. Aspirin should be used cautiously in neonatal animals; adult doses may lead to toxicity.

Adverse Effects

The most common adverse effect of aspirin at therapeutic doses is gastric (nausea, anorexia, vomiting) or intestinal irritation with varying degrees of occult GI blood loss occurring. The resultant irritation may result in vomiting and/or anorexia. Severe blood loss may result in a secondary anemia or hypoproteinemia. In dogs, plain uncoated aspirin may be more irritating to the gastric mucosa than either buffered aspirin or enteric-coated tablets. Misoprostol has been shown to reduce GI bleeding and vomiting in dogs receiving aspirin. Hypersensitivity reactions have been reported in dogs although they are thought to occur rarely. Cats may develop acidosis from aspirin therapy.

Reproductive/Nursing Safety

Salicylates are possible teratogens and have been shown to delay parturition; their use should be avoided during pregnancy, particularly during the later stages. In humans, the FDA categorizes this drug as category D for use during pregnancy (There is evidence of human fetal risk, but the potential benefits from the use of the drug in pregnant women may be acceptable despite its potential risks.) In a separate system evaluating the safety of drugs in canine and feline pregnancy (Papich 1989), this drug is categorized as class: C (These drugs may have potential risks. Studies in people or laboratory animals have uncovered risks, and these drugs should be used cautiously as a last resort when the benefit of therapy clearly outweighs the risks.)

Overdosage/Acute Toxicity

Clinical signs of acute overdosage in dogs and cats include: depression, vomiting (may be blood tinged), anorexia, hyperthermia, and increased respiratory rate. Initially, a respiratory alkalosis occurs with a compensatory hyperventilation response. A profound metabolic acidosis follows. If treatment is not provided, muscular weakness, pulmonary and cerebral edema, hypernatremia, hypokalemia, ataxia, and seizures may all develop with eventual coma and death.

There were 1939 single agent exposures to aspirin reported to the ASPCA Animal Poison Control Center (APCC) during 2009-2013. There were 1749 dogs exposed, 712 of which were symptomatic. The most common signs included: vomiting (75%), lethargy (21%), panting (9%), hyperthermia (8%), and bloody vomiting (7%). Of the 177 cats, 54 were symptomatic with 56% vomiting, 22% anorexic, 13% lethargic and 6% with bloody vomiting.

Treatment of acute overdosage initially consists of emptying the gut if ingestion has occurred within 12 hours, giving activated charcoal and an oral cathartic, placing an intravenous line, beginning fluids and drawing appropriate lab work (e.g., blood gases). Some clinicians suggest performing gastric lavage with a 3-5% solution of sodium bicarbonate to delay the absorption of aspirin. A reasonable choice for an intravenous solution to correct dehydration would be dextrose 5% in water. Acidosis treatment and forced alkaline diuresis with sodium bicarbonate should be performed for serious ingestions, but should only be attempted if acid-base status can be monitored. Diuresis may be enhanced by the administration of mannitol (1 – 2 grams/kg/hour). GI protectant medications should also be administered. Seizures may be controlled with IV diazepam. Treatment of hypoprothrombinemia may be attempted by using phytonadione (2.5 mg/kg divided q8-12h) and ascorbic acid (25 mg parenterally) but ascorbic acid may negate some of the urinary alkalinization effects of bicarbonate. Peritoneal dialysis or exchange transfusions may be attempted in very severe ingestions when heroic measures are desired.

Drug Interactions

The following drug interactions with aspirin have either been reported or are theoretical in humans or animals 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.

  • Aminoglycosides: Some clinicians feel that aspirin should not be given concomitantly with aminoglycoside antibiotics because of an increased likelihood of nephrotoxicity developing. The actual clinical significance of this interaction is not clear, and the risks versus benefits should be weighed when contemplating therapy.
  • Corticosteroids: May increase the clearance of salicylates, decrease serum levels and increase the risks for GI bleeding. One dog study showed no significant difference in gastric mucosal injury when ultra-low dose (0.5 mg/kg/day) aspirin was added to prednisone therapy. Addition of aspirin did increase the incidence of mild, self-limiting diarrhea (Graham et al. 2009).
  • Digoxin: In dogs, aspirin has been demonstrated to increase plasma levels of digoxin by decreasing the clearance of the drug.
  • Furosemide: May compete with the renal excretion of aspirin and delay its excretion; this may cause clinical signs of toxicity in animals receiving high aspirin doses. Furosemide diuretic effect may be diminished.
  • Heparin or Oral Anticoagulants: Aspirin may increase the risks for bleeding.
  • Methotrexate: Aspirin may displace MTX from plasma proteins increasing the risk for toxicity.
  • NSAIDs: Increased chances of developing GI ulceration exist. Animals that have been on aspirin therapy that will be replaced with a COX-2 NSAID, should probably have a “wash out” period of 3-10 days between stopping aspirin and starting the NSAID (Bill 2008). Another recommendation for cats is a “washout period” of approximately 7-10 days when switching from aspirin to another NSAID (Sparkes et al. 2010).
  • Phenobarbital May increase the rate of metabolism of aspirin by inducing hepatic enzymes.
  • Probenecid, Sulfinpyrazone: At usual doses, aspirin may antagonize the uricosuric effects of probenecid or sulfinpyrazone.
  • Spironolactone: Aspirin may inhibit the diuretic activity of spironolactone.
  • Tetracycline: The antacids in buffered aspirin may chelate tetracycline products if given simultaneously; space doses apart by at least one hour.
  • Urinary acidifying drugs (e.g., methionine, ammonium chloride, ascorbic acid): Can decrease the urinary excretion of salicylates.
  • Urinary Alkalinizing Drugs: (e.g., acetazolamide, sodium bicarbonate) significantly increase the renal excretion of salicylates; because carbonic anhydrase inhibitors (e.g., acetazolamide, dichlorphenamide) may cause systemic acidosis and increase CNS levels of salicylates; toxicity may occur.

Laboratory Considerations

  • At high doses, aspirin may cause false-positive results for urinary glucose if using the cupric sulfate method (Clinitest®, Benedict’s solution) and false-negative results if using the glucose oxidase method (Clinistix® or Tes-Tape®).
  • Urinary ketones measured by the ferric chloride method (Gerhardt) may be affected if salicylates are in the urine (reddish-color produced). Salicylates may interfere with fluorescent methods for determining urine 5-HIAA. Falsely elevated VMA (vanillylmandelic acid) may be seen with most methods used if salicylates are in the urine. Falsely lowered VMA levels may be seen if using the Pisano method.
  • Urinary excretion of xylose may be decreased if aspirin is given concurrently. Falsely elevated serum uric acid values may be measured if using colorimetric methods.
  • Aspirin can decrease serum concentrations of total T4.

Doses

Note: There are no approved FDA-Products/Dosages; all dosages are extra-label.

Dogs:

  • To decrease platelet aggregation; as an antithrombotic (extra-label): The ideal aspirin dosage, if any, for prevention of thromboembolism in dogs is unknown (data conflicts, study limitations, etc.) (Smith 2012). Commonly, dosages of 0.5 – 1 mg/kg PO once a day are recommended, but some recommend up to 10 mg/kg PO once a day. A preliminary report demonstrated that platelet activity is increased in dogs with IMHA as compared to normal dogs and that neither low dose aspirin (0.5 mg/kg/day PO) nor individually dosed heparin suppresses platelet thromboxane release in vivo(Stiller et al. 2013).
  • As an analgesic/antipyretic/antiinflammatory (extra-label): Anecdotal dosages usually range from 10 – 20 mg/kg of buffered aspirin PO twice daily. Anecdotal antiinflammatory dosages are slightly higher (20 – 30 mg/kg q8-12h), but canine-approved NSAIDs generally have significantly fewer gastrointestinal effects and are usually preferred.

Cats:

  • For analgesia/antipyrexia/antiinflammatory (extra-label): Anecdotal dosage recommendation is usually 10 mg/kg PO every 2-3 days; practically: ½ to one 81 mg tablet (“baby aspirin”) Monday, Wednesday, Friday of each week.
  • As an antithrombotic agent (extra-label): Two basic dosage regimens have been recommended, “high dose” and “low dose”; it is unknown if one is superior to the other with regard to efficacy, but “high dose” appears to have a significantly higher risk for causing GI effects. High-dose: As above (10 mg/kg PO q2-3 days; ½ – 1 “baby aspirin” every 2-3 days (M-W-F). Low-dose: 5 mg per cat PO every 3rd day.

Ferrets:

  • As an analgesic (extra-label): 10 – 20 mg/kg PO once daily (has short duration of activity). (Williams 2000)

Rabbits/Rodents/Small Mammals:

Note: All are extra-label.

  • Rabbits: 5 – 20 mg/kg PO once daily for low-grade analgesia. (Ivey et al. 2000)
  • Mice, Rats, Gerbils, Hamsters: 100 – 150 mg/kg PO q4h. Guinea pigs: 87 mg/kg PO. (Adamcak et al. 2000)

Horses: (NOTE: ARCI UCGFS CLASS 4 DRUG)

  • For anti-platelet activity as an adjunctive treatment of laminitis (extra-label): 5 – 10 mg/kg PO q24-48 hours or 20 mg/kg PO every 4-5 days. (Brumbaugh et al. 1999)

Monitoring

  • Analgesic effect &/or antipyretic effect.
  • Bleeding times if indicated.
  • PCV and stool guaiac tests if indicated.

Client Information

  • Contact veterinarian if symptoms of GI bleeding or distress occur (e.g., black, tarry feces; anorexia or vomiting, etc.).
  • Because aspirin is a very old drug, formal approvals from the FDA for its use in animals have not been required. There is no listed meat or milk withdrawal times listed for food-producing animals but because there are salicylate-sensitive people, in the interest of public health, this author suggests a minimum of 1 day withdrawal time for either milk or meat.

Chemistry/Synonyms

Aspirin, sometimes known as acetylsalicylic acid or ASA, is the salicylate ester of acetic acid. The compound occurs as a white, crystalline powder or tabular or needle-like crystals. It is a weak acid with a pKa of 3.5. Aspirin is slightly soluble in water and is freely soluble in alcohol. Each gram of aspirin contains approximately 760 mg of salicylate.

Aspirin may also be known as: ASA, acetylsal acid, acetylsalicylic acid, acidum acetylsalicylicum, polopiryna, or salicylic acid acetate; many trade names are available.

Storage/Stability

Aspirin tablets should be stored in tight, moisture resistant containers. Do not use products past the expiration date or if a strong vinegar-like odor is noted emitting from the bottle.

Aspirin is stable in dry air, but readily hydrolyzes to acetate and salicylate when exposed to water or moist air; it will then exude a strong vinegar-like odor. The addition of heat will speed the rate of hydrolysis. In aqueous solutions, aspirin is most stable at pH’s of 2-3 and least stable at pH’s <2 or >8. Should an aqueous solution be desirable as a dosage form, the commercial product Alka-Seltzer® will remain stable for 10 hours at room temperature in solution.

Compatibility/Compounding Considerations

Compounded preparation stability: Aspirin is hydrolyzed by water to degradative byproducts, acetic acid and salicylic acid.

Effervescent buffered aspirin tablets (Alka-Seltzer®) dissolved in water are demonstrated to be stable for 10 hours at room temperature and for 90 hours if refrigerated (McEvoy 2008). Although pharmacists compound aspirin suspensions in fixed oils, the long-term stability of these preparations has not been determined.

Dosage Forms/Regulatory Status

Veterinary-Labeled Products:

Note: No known products are FDA-approved for use in animals.

Aspirin Tablets (Enteric-Coated): 81 mg; (OTC). Labeled for use in dogs.

Aspirin Tablets (Buffered, Microencapsulated, Chewable for dogs): 150 mg & 450 mg; Canine Aspirin Chewable Tablets for Small & Medium (150 mg) or Large Dogs® (450 mg); (OTC). Labeled for use in dogs.

Aspirin Tablets 60 grain (3.9 g): Aspirin 60 Grain (OTC & Rx); Rx is labeled for use in horses, cattle, sheep and swine; not for use in horses intended for food or in lactating dairy animals.

Aspirin Boluses 240 grain (15.6 g): Labeled for use in horses, foals, cattle and calves; not for use in lactating animals. Aspirin 240 Grain Boluses, Aspirin Bolus (various); (OTC)

Aspirin Boluses 480 grain (31.2 g). Labeled for use in mature horses, & cattle. Aspirin 480 Grain Boluses (various); (OTC)

Oral Aspirin Gel: 250 mg/mL in 30 mL: Aspir-Flex® Aspirin Gel for Small and Medium Dogs; 500 mg/1 mL in 30 mL: Aspir-Flex® Aspirin Gel for Large Dogs; (OTC). Labeled for use in dogs.

Aspirin Powder: l lb. (various); (OTC); Aspirin Powder Molasses-Flavored 50% acetylsalicylic acid in base; Aspirin USP 204 g/lb. (apple flavored); Acetylsalicylic acid; (OTC)

Aspirin Granules: 2.5 gram per 39 mL scoop (apple and molasses flavor); Arthri-Eze Aspirin Granules®; (OTC); Labeled for use in horses

Aspirin Liquid Concentrate (equiv. to 12% aspirin) for Dilution in Drinking Water in 32 oz. btls.; (OTC). Labeled for addition to drinking water for swine, poultry, beef and dairy cattle

There are no listed meat or milk withdrawal times listed for food-producing animals, but because there are salicylate-sensitive people, in the interest of public health, this author suggests a minimum of 1 day withdrawal time for either milk or meat. For further guidance with determining use and withdrawal times, contact FARAD (see Phone Numbers & Websites in the appendix for contact information).

The ARCI (Racing Commissioners International) has designated this drug as a class 4 substance. See the appendix for more information.

Human-Labeled Products:

Aspirin, Chewable Tablets: 81 mg (1.25 grain); many trade names, generic; (OTC)

Aspirin, Tablets; plain uncoated; 325 mg (5 grain), & 500 mg (7.8 grain); many trade names, generic; (OTC)

Aspirin Tablets, enteric coated: 81 mg, 165 mg, 325 mg, 500 mg, 650 mg, & 800 mg; many trade names, generic; (OTC)

Aspirin Extended-controlled Release Tablets: 81 mg, 650 mg, 800 mg & 975 mg; many trade names, generic; (OTC)

Aspirin, Tablets; buffered uncoated; 325 mg (5 grain), with aluminum &/or magnesium salts; many trade names, generic; (OTC)

Aspirin Tablets: buffered coated: 325 mg & 500 mg; many trade names, generic; (OTC)

Rectal suppositories, chewing gum and effervescent oral dosage forms are also available commercially for human use.

Revisions/References

Monograph revised/updated August 2013.

Adamcak, A. & B. Otten (2000). Rodent Therapeutics. Vet Clin NA: Exotic Anim Pract 3:1(Jan): 221-40.

Bill, R. (2008). NSAIDs--Keeping up with all the changes. Proceedings: ACVC.

Brumbaugh, G., et al. (1999). The pharmacologic basis for the treatment of laminitis. The Veterinary Clinics of North America: Equine Practice 15:2(August).

Coetzee, J. F. (2013). Assessment and Management of Pain Associated with Castration in Cattle. Veterinary Clinics of North America-Food Animal Practice 29(1): 75-+.

Graham, A. H. & M. S. Leib (2009). Effects of Prednisone Alone or Prednisone with Ultralow-Dose Aspirin on the Gastroduodenal Mucosa of Healthy Dogs. Journal of Veterinary Internal Medicine 23(3): 482-7.

Ivey, E. & J. Morrisey (2000). Therapeutics for Rabbits. Vet Clin NA: Exotic Anim Pract 3:1(Jan): 183-216.

McEvoy, J., Ed. (2008). AHFS Drug Information. Bethesda, American Society of Health System Pharmacists.

Shearer, L., et al. (2009). Effects of aspirin and clopidogrel on platelet function in healthy dogs. Proceedings: ECVIM. accessed via Veterinary Information Network; vin.com

Smith, S. A. (2012). Antithrombotic Therapy. Topics in Companion Animal Medicine 27(2): 88-94.

Sparkes, A. H., et al. (2010). ISFM AND AAFP CONSENSUS GUIDELINES Long-term use of NSAIDs in cats. Journal of Feline Medicine and Surgery 12(7): 521-38.

Stiller, A., et al. (2013). Effect of Low-Dose Aspirin or Heparin on Platelet-Derived Urinary Thromboxane Metabolite in Dogs with Immune-Mediated Hemolytic Anemia (IMHA). ACVIM Proceedings. accessed via Veterinary Information Network; vin.com

Williams, B. (2000). Therapeutics in Ferrets. Vet Clin NA: Exotic Anim Pract 3:1(Jan): 131-53.

January 1, 2005 (published) | January 1, 2015 (revised)

Expert:  Dr. Jo replied 9 months ago.

Hello,

I'm just checking in to ask how Daisy is doing. Is she doing any better?

Thank you.

Dr. Jo