Q&A With Christopher G. Byers, DVM, DACVECC, DACVIM

dvm360:Starting with your name, can you tell me a little bit about your background?

I’m a practicing diplomate of the American College of Veterinary Emergency and Critical Care, a board-certified small animal internal medicine specialist, and a certified veterinary journalist based in Omaha, Nebraska. I’m a proud graduate of Cornell University’s College of Veterinary Medicine [in Ithaca, New York], and have a passion for education and sharing my experiences with colleagues. Clinically, I love hematology, endocrinology, sepsis, and fluid therapy.

dvm360:Why is it critical to differentiate between vomiting, regurgitation, and passive expulsion before initiating antiemetic therapy?

It’s essential to distinguish these processes because they point to very different underlying problems, and only one of them (true vomiting) actually benefits from antiemetic therapy. Vomiting is an active, centrally mediated process, so antiemetics can be both therapeutic and diagnostic. Regurgitation, on the other hand, is a passive event tied to esophageal dysfunction or obstruction, and antiemetics won’t help and may actually delay appropriate diagnostics. Passive expulsion can indicate severe systemic illness or neuromuscular weakness and likewise doesn’t respond to antiemetics. Making the distinction up front keeps clinical reasoning on track and prevents us from masking signs we really need to see.

dvm360:Why might a dog that is vomiting due to sepsis not respond as effectively to metoclopramide as a dog vomiting due to dietary indiscretion?

Metoclopramide primarily works as a dopamine (D2) antagonist and as a mild prokinetic, so it’s most effective when the emetic trigger is within that dopaminergic pathway or related to delayed gastric emptying. In sepsis, the emetic drive is often multifactorial: Cytokine release, altered blood-brain barrier permeability, endotoxin effects, and sometimes concurrent organ dysfunction all play a role. Those pathways bypass the classic D2-mediated emetic mechanisms, making metoclopramide a relatively weak tool in that scenario. In contrast, vomiting from simple dietary indiscretion is far more likely to respond because the emetic stimulus is less complex and more aligned with the mechanisms metoclopramide actually targets.

dvm360:There are different routes of administration for maropitant. In an emergency setting with a patient with severe pain or a very critical condition, which route do you choose and why?

In most emergency situations with painful or unstable patients, I reach for the IV [intravenous] route. It’s rapid, reliable, and avoids the discomfort often associated with the subcutaneous injection. The onset is quick, exactly what you want in a crashing or severely nauseated patient, and it allows us to maintain patient comfort without adding an

unnecessary pain point. If IV access truly isn’t an option, then the subcutaneous route is a reasonable fallback, but in a real emergency, IV is almost always the best fit.

dvm360:Maropitant injection is known to cause pain upon administration. Based on evidence or established practice, what are 2 practical steps a veterinary professional can take to minimize this discomfort for the patient?

Two reliably effective and evidence-based ways to reduce maropitant’s injection sting are:

• Administer the drug cold, straight from the refrigerator (around 4 °C). Cooling the solution reduces nociceptor activation and has consistently been shown to lessen the characteristic maropitant burn. It’s simple, inexpensive, and makes a noticeable difference in patient comfort.
• Inject slowly and intentionally. A slower injection rate minimizes tissue stretch and mechanical irritation, which helps keep patients far more comfortable, especially those who are already painful or systemically fragile.

If appropriate, clinicians can also rotate injection sites and, when available, choose the benzyl alcohol–containing formulation, which is associated with reduced pain during injection.

Importantly, even though some clinicians try mixing maropitant with subcutaneous fluids to dilute the sting, we avoid doing so. The manufacturer advises against it due to pH incompatibilities and lack of stability data, and pharmacokinetic studies show that coadministration with SC [sodium chloride] crystalloids can significantly delay absorption and reduce systemic exposure, up to a 30% drop in bioavailability. In acute or perioperative cases where rapid, predictable antiemetic effect is critical, that loss of efficacy is clinically meaningful.