QUARTERLY BEAT / APRIL 2022 ///
SEE THE DIFFERENCE Pain and dysphoria don’t have to be part of the post-op experience. *
ISONIAZID Isoniazid (commonly known as INH) is a human medication used for tuberculosis. While it is used in veterinary medicine to treat Mycobacterium or Actinomyces, it has a narrow margin of safety in dogs and cats. This drug works by blocking the synthesis of mycolic acid. INH depletes the CNS of pyridoxine and also decreases levels of GABA within the brain. Many assume that since this is an “antibiotic” that it is safe; however, when accidentally ingested in dogs (and rarely, cats), it can result in severe CNS signs (e.g., tremors, refractory seizures, coma, death). The LD 50 in dogs is estimated to be as low as 50 mg/kg; at this same dose, seizures can be seen. One 300 mg tablet can result in severe poisoning in a 10-pound dog. Other clinical signs include GI signs (e.g., hypersalivating, vomiting, diarrhea), acid-base disturbances (e.g., metabolic acidosis), hyperthermia (secondary to tremors or seizures) and organ injury (e.g., hepatic injury, acute kidney injury, etc.). Due to the rapid onset of clinical signs, it is often too late to decontaminate the patient. Gastric lavage under anesthesia may be necessary. Treatment also includes IV fluids, ant-emetics, anticonvulsants, muscle relaxants, supportive care, and the antidote pyridoxine hydrochloride (typically available as 100 mg/ml) (Dose: suggested dose of 71 mg/kg IV, diluted to 5-10%, slow over 30-60 minutes). Clinicopathologic monitoring should include a biochemistry panel and recheck hepatic panel (3-5 days later). 5-FLUOROURACIL (5-FU) The most life-threatening topical toxin to dogs and cats is 5-fluorouracil (5-FU). 5-FU, commonly known by the brand names Efudex®, Carac®, Adrucil®, and Fluoroplex®, is a prescription anti-neoplastic medication that is often used for treatment of actinic keratosis or superficial basal cell carcinoma in humans. It is commonly sold in low concentration products (e.g., 0.5-5%), and works by inhibiting DNA and RNA synthesis and production, resulting in programmed cell death. 8 While IV administration of 5-FU is occasionally used as a chemotherapeutic agent in dogs (e.g., for mammary gland tumor, etc.), it is not recommended for use in cats. Decades ago, topical 5-FU was used in cats for the treatment of squamous cell carcinoma; however, it resulted in severe toxicosis and death due to its narrow margin of safety. Clinical signs of 5-FU toxicosis can often be seen within 30 minutes up to 6 hours; death has been reported as early as 7 hours. 8 Clinical signs include acute GI signs (e.g., hypersalivation, anorexia, vomiting, abdominal pain, diarrhea, bloody diarrhea, etc.), CNS signs (e.g., ataxia, tremors, seizures), and bone marrow suppression (e.g., anemia, leukopenia, thrombocytopenia). 8 The lowest reported toxic (oral) dose in dogs is 6 mg/kg, while the minimal reported lethal dose is 20 mg/kg. One case report did have a dog survive ingestion of 46 mg/kg of 5-FU. 8 That said, the prognosis with 5-FU toxicosis is typically grave in cats and guarded in dogs (with a reported survival in dogs of approximately 25%). Death typically occurs
due to secondary complications from the 5-FU such as sepsis (due to leukopenia), increased intracranial pressure (due to persistent seizures), intracranial hemorrhage (due to severe thrombocytopenia), or DIC (due to severe seizures). Unfortunately, most patients present with severe clinical signs, where it is too late to perform decontamination. Therefore, treatment should be aimed at symptomatic supportive care, anti-convulsant therapy, anti-emetics, anti-diarrheals, IV fluids (to help maintain perfusion), thermoregulation, broad-spectrum antibiotics, clinicopathologic monitoring, and symptomatic supportive care. If the patient is able to survive the acute crisis, clinicopathologic monitoring is necessary every 3-4 days thereafter for 2-3 weeks, until bone marrow function returns to normal. 8 CONCLUSION Pet owners should be appropriately educated on how to pet-proof the house and be trained on what common human medications can be toxic to pets. Pet owners should also be appropriately educated on crate training to help minimize toxin exposure. When in doubt, the ASPCA Animal Poison Control Center should be consulted for toxic ingestions that veterinarians are unaware of.
References available upon request.
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Controls Pain to Help Post-Op Return to Function
Single-Dose Administration
FDA-Approved
U P T O 7 2 - H O U R A N A L G E S I A
Long-Acting Local Anesthetic
Canine CCL ** and feline onychectomy patients can recover comfortably even after going home.
Recovery care begins with Nocita™
Indications For single-dose infiltration into the surgical site to provide local postoperative analgesia for cranial cruciate ligament surgery in dogs. For use as a peripheral nerve block to provide regional postoperative analgesia following onychectomy in cats. Important Safety Information NOCITA is for use in dogs and cats only. Do not administer concurrently with bupivacaine HCl, lidocaine or other amide local anesthetics. The safe use of NOCITA in dogs and cats with cardiac disease or with hepatic or renal impairment has not been evaluated. The safe use in dogs or cats younger than 5 months of age, that are pregnant, lactating, or intended for breeding has not been evaluated. The most common adverse reactions in dogs were discharge from incision, incisional inflammation and vomiting. The most common adverse reactions in cats were elevated body temperature and infection or chewing/licking at the surgical site. Please see accompanying brief summary for product safety information. *In a field trial, Nocita reduced the need for post-op rescue pain treatment with opioids **Cranial cruciate ligament Nocita, Elanco and the diagonal bar logo are trademarks of Elanco or its affiliates. ©2021 Elanco or its affiliates. PM-US-21-1709
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