Motion sickness is a condition in which the brain receives conflicting input from three main sensory systems that track balance and movement: the vestibular system of the inner ear, the eyes, and the body's muscles and joints. As a result of this conflicting sensory information, a stress response is triggered in the brain, resulting in common clinical signs including nausea, vomiting, salivation, and agitation.
Motion sickness is characterized by clinical signs referable to stimulation of the vestibular and autonomic nervous systems, including vomiting, which is often preceded by nausea.
Nausea is complex; it is affected not only by vestibular inputs but also by other factors associated with somatic and physical stress and GI stimulation. Animals, like people, feel nausea that is recognized clinically by signs including the following:
salivation
lip licking
vocalization (whining)
restlessness (panting, turning, circling, digging)
lethargy
Severely affected animals can also develop diarrhea and vomiting.
A behavioral assessment using a numerical rating scale can be used to monitor the severity of nausea (1). Autonomic nervous system signs (salivation, sweating, and vasoconstriction) occur simultaneously with the sensation of nausea. Motion sickness can occur during travel by land, sea, and air, and clinical signs usually disappear when vehicular motion ceases.
The principal causative mechanism in motion sickness involves stimulation of the vestibular apparatus in the inner ear, which is connected to the emetic center in the brainstem. The vestibular nuclei are central in relaying vestibular information and are involved in the pathway for induction of nausea in the nucleus tractus solitarius. Attention has been focused on the 5-HT3 receptors that mediate serotonergic inhibition of pyramidal cell populations and are found in the brainstem, forebrain, and spinal cord. High numbers of 5-HT3 receptors in the vestibular system and area postrema indicate stimulus areas for nausea and vomiting. The chemoreceptor trigger zone (CRTZ) and H1histamine receptors are involved in this pathway in dogs but apparently are less important in cats.
Recent evidence has revealed that the neurokinin-1 (NK-1) substance P receptors in the emetic center play a major role in motion sickness in both dogs and cats and are more important than the receptors in the CRTZ (2). Fear of the vehicle can also become a contributory factor in dogs and cats that develop a conditioned response to the event; they may exhibit clinical signs even in a stationary vehicle. In this situation, either behavioral modification to eliminate this fear or drugs to provide a sedative effect might be needed.
Nausea is pharmacologically more difficult to manage than vomiting. In some cases, motion sickness can be overcome by conditioning the animal to travel. In others, anxiolytic and antinausea drugs can be used with good results. Antihistamines (such as diphenhydramine hydrochloride, dimenhydrinate, meclizine, and promethazine hydrochloride) prevent motion sickness, provide sedation, and inhibit drooling. The centrally acting phenothiazine derivatives (such as chlorpromazine, prochlorperazine, and acepromazine maleate) have antiemetic as well as sedative effects. Cats have no histamine receptors in the CRTZ; therefore, antihistamines are ineffective in treating motion sickness in this species. Instead of administering a pure H1 histamine antagonist, veterinarians treating motion sickness in cats are better off prescribing maropitant (an NK-1 receptor antagonist).
Pearls & Pitfalls
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Drugs Used for Motion Sickness in Dogs and Cats
Drug | Mechanism of Action | Dose in Dogs | Dose in Cats | Comments |
|---|---|---|---|---|
Chlorpromazine HCl | D2 dopamine antagonist, 5-HT3 effects; antihistamine and alpha-adrenergic antagonist | 0.5 mg/kg, IV, IM, SC, q 8 h; 1–3 mg/kg, PO, up to q 6 ha | Questionable efficacy in catsb,c | Inhibits apomorphine-induced emesis in dogs; may potentiate seizures |
Prochlorperazine | Phenothiazine derivative Multiple mechanisms of action, including antagonism of dopamine, histamine type 1, alpha-2-adrenergic and muscarinic receptors | 0.17–0.7 mg/kg, IM, SC, q 6–12 hd | 0.1–0.5 mg/kg, SC, q 8 he | Antiemetic |
Meclizine HCl | Piperazine derivative; antihistamine | 12.5 mg/dog, PO, q 12 hf | Not effective in cats | Give 1 h before travel for motion sickness |
Diphenhydramine HCl | Antihistamine | 2–4 mg/kg, PO, IM, q 8 hg | Not effective in cats | Prevents motion sickness; is sedative, antiemetic |
Dolasetron mesylateh | 5-HT3 receptor antagonist | 0.6 mg/kg, IV or PO, q 24 h | 0.6 mg/kg, IV or PO, q 24 h | Useful for chemotherapy-related nausea |
Ondansetron HCl dihydrate | 5-HT3 receptor antagonist | 0.3–1 mg/kg, IV (slowly) or PO, q 8–12 hi,j,k | 0.5–1 mg/kg, PO, SC, IM, or IV (slowly), q 8 hl | Use caution in dogs with MDR1 gene mutation; give IV 30 min before chemotherapy |
Metoclopramide | D2 dopamine antagonist, mild 5-HT3 effects | 0.2–0.5 mg/kg PO, SC, IM, IV, q 6–8 h;1–2 mg/kg/day, IV CRIm,n | 0.2–0.5 mg/kg PO, SC, IM, IV, q 6–8 h; 1–2 mg/kg/day, IV CRIm | Do not use in GI obstruction, with phenothiazines or narcotic analgesics |
Maropitant | NK-1 receptor antagonist | 1 mg/kg SC, q 24 h, or 2 mg/kg, PO, q 24 h up to 5 consecutive days; motion sickness: 8 mg/kg, PO, q 24 h until resolution of acute vomiting (for dogs > 7 mo old)o,p | 1 mg/kg, SC, IV, or PO, q 24 h for up to 5 consecutive daysq | Dose 2 hours before travel; not recommended in animals < 16 weeks old; SC route may cause pain on injection |
aHall J. Diseases of the stomach. In: Ettinger S, Feldman E, eds. Textbook of Veterinary Internal Medicine: Diseases of the Dog and Cat. Vol 1. WB Saunders; 2000:1154-1182. bOgeer J. Chlorpromazine HCl (Thorazine). DVMetrics North American Companion Animal Formulary. 14th ed. Revised January 18, 2024. c Posner L, Burns P. Sedative agents: tranquilizers, alpha-2 agonists and related agents. In: Riviere J, Papich M, eds. Veterinary Pharmacology and Therapeutics. 9th ed. Wiley-Blackwell; 2009:337-380. d Niemegeers CJ.Antiemetic specificity of dopamine antagonist. Psychopharmacology. 1982:78(3):210-213. doi:10.1007/BF00428152 e Trepanier L. Acute vomiting in cats. J Feline Med Surg. 2010;12(3):225-230. doi:10.1016/j.jfms.2010.01.005 f Garosi LS, Lowrie ML, Swinbourne NG. Neurological manifestations of ear disease in dogs and cats. Vet Clin North Am Small Anim Pract. 2012;42(6):1143-1160. doi:10.1016/j.cvsm.2012.08.006 g Platt SR. Vestibular disease. In: Silverstein DC, Hopper K, eds. Small Animal Critical Care Medicine. 2nd ed. Elsevier Saunders; 2015:452-458. h Ogilvie GK. Dolasetron: a new option for nausea and vomiting. J Am Anim Hosp Assoc. 2000;36(6):481-483. doi:10.5326/15473317-36-6-481 i Soetelo CK, Shropshire SB, Quimby J, Simpson S, Gustafson DL, Zersen KM. Pharmacokinetics and anti-nausea effects of intravenous ondansetron in hospitalized dogs exhibiting clinical signs of nausea. J Vet Pharmacol Ther. 2022;45(6):508-515. doi:10.1111/jvp.13087 j Kenward H, Elliott J, Lee T, Pelligand L. Anti-nausea effects and pharmacokinetics of ondansetron, maropitant and metoclopramide in a low-dose cisplatin model of nausea and vomiting in the dog: a blinded crossover study. BMC Vet Res. 2017;13(1):244-256. doi:10.1186/s12917-017-1156-7 k Foth S, Meller S, Kenward H, Elliott J, Pelligand L, Volk HA. The use of ondansetron for the treatment of nausea in dogs with vestibular syndrome. BMC Vet Res. 2021;17(1):222-231. doi:10.1186/s12917-021-02931-9 l Quimby JM, Lake RC, Hansen RJ, Lunghofer PJ, Gustafson DL. Oral, subcutaneous, and intravenous pharmacokinetics of ondansetron in healthy cats. J Vet Pharmacol Ther. 2014;37(4):348-353. doi:10.1111/jvp.12094 m Macintire DK, Drobatz KJ, Haskins SC, Saxon WD. Metoclopramide. Manual of Small Animal Emergency and Critical Care Medicine. Wiley-Blackwell; 2012:604. https://onlinelibrary.wiley.com/doi/pdf/10.1002/9781119421870.app10?msockid=02cc6156f0b8695426a8761df1bc688e n Whitehead K, Cortes Y, Eirmann L. Gastrointestinal dysmotility disorders in critically ill dogs and cats. J Vet Emerg Crit Care. 2016;26(2):234-253. doi:10.1111/vec.12449 o US Food and Drug Administration. [Maropitant citrate] injectable solution dogs. Freedom of Information Summary, NADA 141-263. Approved January 29, 2007. https://animaldrugsatfda.fda.gov/adafda/app/search/public/document/downloadFoi/818 p US Food and Drug Administration. Maropitant citrate tablets dogs. Freedom of Information Summary, ANADA 200-833. Approved January 12, 2026. https://animaldrugsatfda.fda.gov/adafda/app/search/public/document/downloadFoi/17886 q Hickman MA, Cox SR, Mahabir S, et al. Safety, pharmacokinetics and use of the novel NK-1 receptor antagonist maropitant (Cerenia) for the prevention of emesis and motion sickness in cats. J Vet Pharmacol Ther. 2008;31(3):220-229. doi:10.1111/j.1365-2885.2008.00952.x | ||||
Maropitant, an NK-1 receptor antagonist, is effective in treating motion sickness in dogs. NK-1 receptors are located in the emetic center of the brainstem, which is another source of the vomiting and nausea of motion sickness. Blocking the NK-1 receptors is more effective in treating motion sickness than inhibiting the CRTZ. Maropitant is FDA-approved and is the preferred drug to treat motion sickness in dogs. The drug is administered once daily to dogs in tablet and injectable forms; only the injectable form is FDA-approved for use in cats. However, cats can exhibit severe aversive and pain behaviors to SC injection. Pain is associated with the amount of unbound maropitant, which is altered by temperature; when refrigerated, more maropitant is bound and reaction to injection is less (3). Cats should be 16 weeks old and dogs 8 weeks old before being administered maropitant.
Nausea can be induced by anticipatory experiences related to fear or anxiety. Anxiolytic and sedative medications are commonly prescribed to decrease stressful experiences in veterinary practices that may induce nausea.
Gabapentin is an alpha-2-delta ligand, which can have an inhibitory effect on calcium voltage-gated channels that decrease release of excitatory neurotransmitters. In cats, gabapentin is frequently administered as an anxiolytic (100 mg/cat, PO, 90 minutes before transport) (4).
Trazodone (dogs: 5–7.5 mg/kg, PO, 90 minutes before event; can combine with gabapentin, 10 mg/kg, PO [5]; cats: 50 mg/cat, PO, 60–90 minutes before event; 5 mg/kg, PO, 2 hours prior to event combined with gabapentin [6, 7]) is classified as a serotonin 5-HT2A antagonist and functions as a serotonin reuptake inhibitor. These medications are strategically administered alone or, if needed, in combination 1 to 2 hours before the event or travel; sometimes the same dose is given the evening before. The medications are well tolerated and effective in minimizing stress and fear-related behaviors. However, adverse effects in some animals can include incoordination and sedation that can influence an accurate neurological examination; effects might be more apparent in older animals and those with comorbidities.
Phenobarbital and diazepam can be used to produce a general sedative effect if anxiety is a problem.Oral administration of one of these drugs several hours before departure should decrease or eliminate the clinical signs of motion sickness; however, oral diazepam should be avoided in cats (8). (Also see Drugs Used to Control or Stimulate Vomiting in Monogastric Animals.)
Key Points
Assessment of nausea is difficult in animals and may be hard to confirm definitively. Behavioral assessments are important for common clinical signs of nausea, including salivation, lip licking, vocalization, restlessness, and lethargy.
Nausea is a complex clinical sign of motion sickness and is induced by many physical and stress factors.
Pharmacological treatments for motion sickness target different receptors in the neural pathway to remedy nausea and vomiting.
Preemptive treatment with sedatives and/or anxiolytics can lessen nausea in stressful environments.
For More Information
Kenward H. Development of an Objective Means of Assessing Nausea in Dogs. EThOS British Library; 2015.
Reisen J. Carsickness in dogs: what to know. American Kennel Society.
Causes and treatment of motion sickness in a dog. Today's Veterinary Practice.
Henze L, Foth S, Meller S, et al. Ondansetron in dogs with nausea associated with vestibular disease: a double-blinded, randomized placebo-controlled crossover study. J Vet Intern Med. 2022;36(5):1726-1732.
DuPont A, Zidan N, Lueck LC, Cameron S. Evaluation of gabapentin administration on neurologic examination in 2 different age groups of healthy cat. J Vet Int Med. 2024;38(6):3129-3137.
Also see pet owner content regarding motion sickness in dogs and cats.
References
Kenward H, Pelligand L, Savary-Bataille K, Elliott J. Nausea: current knowledge of mechanisms, measurement and clinical impact. Vet J. 2015;203(1):36-43. doi:10.1016/j.tvjl.2014.10.007
Sharun K, Jambagi K, Arya M, et al. Clinical applications of substance P (neurokinin-1 receptor) antagonist in canine medicine. Arch Razi Inst. 2021;76(5):1175-1182. doi:10.22092/ari.2021.356171.1797
Narishetty ST, Galvan B, Coscarelli E, et al. Effect of refrigeration of the antiemetic Cerenia (maropitant) on pain on injection. Vet Ther. 2009;10(3):93-102. https://pubmed.ncbi.nlm.nih.gov/20037963/
Erickson A, Harbin K, MacPherson J, Rundle K, Overall KL. A review of pre-appointment medications to reduce fear and anxiety in dogs and cats at veterinary visits. Can Vet J. 2021;62(9):952-960. https://pmc.ncbi.nlm.nih.gov/articles/PMC8360309/
Gruen ME, Sherman BL. Use of trazodone as an adjunctive agent in the treatment of canine anxiety disorders: 56 cases (1995–2007). J Am Vet Med Assoc. 2008;233(12):1902-1907. doi:10.2460/javma.233.12.1902
Stevens BJ, Frantz EM, Orlando JM, et al. Efficacy of a single dose of trazodone hydrochloride given to cats prior to veterinary visits to reduce signs of transport- and examination-related anxiety. J Am Vet Med Assoc. 2016;249(2):202-207. doi:10.2460/javma.249.2.202
Ko JC. Anesthetic considerations for dental and oral-facial surgeries. In: Ko JC, ed. Small Animal Anesthesia and Pain Management. 2nd ed. CRC Press; 2019:480-487.
van Beusekom CD, van den Heuvel JJ, Koenderink JB, Russel FG, Schrickx JA, Feline hepatic biotransformation of diazepam: differences between cats and dogs. Res Vet Sci. 2015;103:119-125, doi:10.1016/j.rvsc.2015.09.016
