There are three main types of antiemetics on the veterinary market: metoclopramide, serotonin receptor antagonists and maropitant.
Metoclopramide is a central dopamine receptor agonist. Medical products containing metoclopramide as the active substance have a pronounced prokinetic effect and are contraindicated when a foreign body or intussusception is suspected. Use may be accompanied by signs of central nervous system involvement. In cats, the antiemetic effect of this group is limited because this species has few dopamine receptors.
Ondansetron and other serotonin receptor antagonists are effective antiemetics and may act synergistically with maropitant.
Maropitant is a neurokinin NK1 receptor antagonist and blocks both central and visceral receptors. In addition to its antiemetic effect, maropitant has anti-inflammatory activity and an effect aimed at reducing chronic pain. The target species are dogs and cats.
Numerous studies and years of clinical use of maropitant support its efficacy and safety as a broad-spectrum antiemetic. Maropitant penetrates the central nervous system and can selectively affect NK1 receptors, generally without the development of adverse effects.
Renal clearance of maropitant is low, so dose adjustment is usually not required even in animals with severe kidney disease.
The safety of maropitant has been evaluated in both preclinical and clinical trials. In experimental dogs, three- or fivefold exceedance of the recommended therapeutic dose did not reveal any abnormalities in well-being. Adverse effects observed with more substantial overdose included only increased salivation and muscle tremor.
In cats, the product was well tolerated in a study at a dose ten times higher than recommended and demonstrated safety when used at 5 mg/kg for 15 consecutive days.
NK1 receptors are associated with substance P and participate in the pathophysiology of pain. According to studies, maropitant improved pain scores in mice after visceral surgery and reduced the minimum alveolar concentration of sevoflurane during ovarian ligament traction in ovariohysterectomy. Based on these data, veterinarians in different countries also use the product in the management of chronic visceral pain.
Substance P is a tachykinin neuropeptide involved in the pathogenesis of various inflammatory conditions and is an important mediator of pain transmission. The role of substance P in the pathogenesis of dry eye disease has also been described through its involvement in the maturation of antigen-presenting cells on the ocular surface after exposure to desiccating stress.
According to study data, treatment with a neurokinin receptor antagonist in mice effectively restored tear production function, suppressed the pathogenic T-helper 17 response and noticeably alleviated the course of the disease.
In addition, studies have been conducted on the use of maropitant for pancreatitis treatment. Rodent studies have shown that, in addition to its antiemetic effect, maropitant may inhibit inflammation by blocking NK1 receptors in the pancreas.
Maropitant citrate monohydrate is included in Sheria, an antiemetic indicated for subcutaneous and intravenous use. Thanks to the improved formulation containing benzyl alcohol, administration of the product is not prone to causing injection pain, which may occur when using products from other manufacturers with a different composition.