Checkpoint 4

Checkpoint 4: Clinical Efficacy & Toxicosis

Test your understanding — select answers and reveal explanations

1In veterinary clinical trials evaluating oral cannabidiol (CBD) administration in dogs for refractory idiopathic epilepsy and osteoarthritis, which serum biochemical abnormality is most consistently observed, and what monitoring protocol is clinically indicated?

A. Elevated serum alkaline phosphatase (ALP) and variable alanine aminotransferase (ALT) activity without hepatic synthetic dysfunction; baseline and serial liver enzyme monitoring alongside CYP450 substrate evaluation is recommended. ✓ B. Marked hyperbilirubinemia and hyperammonemia indicative of acute hepatic necrosis; routine liver biopsy prior to therapy is mandatory. C. Severe azotemia with secondary hyperphosphatemia; initiation of renal replacement therapy is required. D. Persistent hypoproteinemia and reduced blood urea nitrogen (BUN) due to direct inhibition of protein synthesis; concurrent anabolic steroid therapy is required.

Explanation: Clinical trials in dogs consistently demonstrate induction of hepatic cytochrome P450 enzymes leading to dose-dependent elevations in serum ALP, and to a lesser extent ALT, without clinical evidence of acute liver failure or hyperbilirubinemia. Baseline and serial serum biochemistry monitoring is recommended, along with vigilance for CYP-mediated drug interactions.

2A 3-year-old canine patient presents following acute ingestion of concentrated Delta-9-tetrahydrocannabinol (THC) concentrates. Which of the following statements regarding clinical toxicosis presentation and emergency management protocols are correct? (Select all that apply)

Select all that apply

A. Classic clinical signs include static ataxia, hyperesthesia, urinary incontinence, bradycardia, and hypothermia. ✓ B. Emesis induction is contraindicated if the patient exhibits neurological depression or antiemetic properties of THC have manifested, due to heightened risk of aspiration pneumonia. ✓ C. Activated charcoal with a cathartic can be administered (if the airway is protected) because THC undergoes enterohepatic recirculation. ✓ D. Intravenous Lipid Emulsion (ILE) therapy is strictly contraindicated due to the risk of worsening lipophilic THC absorption from the gastrointestinal tract.

Explanation: THC toxicosis produces pathognomonic signs including static ataxia, hyperesthesia, urinary incontinence, hypothermia, and bradycardia. Emesis is risky in obtunded patients and often ineffective due to THC's intrinsic antiemetic effect. Activated charcoal administration is effective because THC and its active metabolites undergo enterohepatic recirculation. ILE therapy is not contraindicated; rather, it serves as an effective lipophilic sink for severe, refractory intoxications.

3Regarding the hepatic pharmacokinetics and drug-drug interactions of cannabidiol (CBD) in canine patients, which mechanism accurately describes its effect on concurrent medications metabolized by Cytochrome P450 (CYP450) enzymes?

A. CBD acts as a competitive inhibitor of specific CYP450 isoenzymes (e.g., CYP2C, CYP3A), which can decrease the metabolic clearance and increase serum concentrations of co-administered drugs like phenobarbital. ✓ B. CBD induces CYP1A2 activity exclusively, resulting in rapid sub-therapeutic clearance of polar compounds like levetiracetam. C. CBD forms irreversible covalent bonds with plasma albumin, completely displacing all other protein-bound therapeutics without affecting enzymatic clearance. D. CBD undergoes exclusive renal tubular excretion, bypassing hepatic oxidative metabolism completely.

Explanation: Phytocannabinoids, particularly CBD, act as substrate-inhibitors for several hepatic CYP450 enzymes (such as CYP2C and CYP3A pathways in dogs). Co-administration of CBD with narrow-therapeutic-index drugs metabolized by the liver (such as phenobarbital) can inhibit their metabolic breakdown, increasing circulating drug levels and potential sedation. Levetiracetam is primarily eliminated unchanged by renal mechanisms and is not heavily dependent on hepatic CYP metabolism.

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Clinical Disclaimer

This course is for veterinary continuing education. It does not constitute veterinary advice or a recommendation to prescribe any specific product. No therapeutic claims are made for unapproved products.