Vet360 Vet360 Vol 05 Issue 03 - Page 29

CPD ARTICLE primarily effective against central stimulation. Maropitant has demonstrated efficacy in dietary indiscretion, pancreatitis, canine parvoviral enteritis and gastritis of unknown aetiology 2 . The lack of prokinetic properties with maropitant allows for safer use in patients with suspected gastrointestinal obstruction relative to for example metoclopramide. A single daily dose of maropitant was also shown to be more effective at managing vomiting due to miscellaneous causes compared to metoclopramide administered two to three times daily 3 . Maropitant has become the standard of care in chemotherapy patients due to its efficacy in preventing vomiting following cisplatin and doxorubicin administration. Maropitant has a 24-hour duration of effect in dogs, but is cleared more slowly in cats with a half-life of 13-17 hours compared to only 4-hours in dogs 4 . The dosages vary depending on the formulation and required effect. • The injectable dose of 1mg/kg, q24h, sub- cutaneously should be administered at least 1 hour prior to anaesthesia or chemotherapy for optimal effect. • The oral dose is higher (2mg/kg, q24h) due to decreased oral bioavailability but food does not affect oral drug absorption. The intravenous use of maropitant is reportedly well tolerated off-label. A 2-day rest period is recommended following the label dosing maximum of 5 consecutive days of administration. This is due to saturation of the hepatic cytochrome p-450 enzymes responsible for its biotransformation. However, a dose of 2 mg/kg, orally, once daily in healthy beagles was safely administered to healthy beagles for 14 days 5 . Maropitant undergoes primarily hepatic clearance and little renal clearance, which suggests that doses are unlikely to need reduction in renal dysfunction be the drug must be avoided in cases with hepatic dysfunction. In cats, maropitant is approved for injectable use but oral tablets are also commonly prescribed off-label. The drug is highly protein bound which may cause interactions with other highly protein bound drugs such as some non-steroidal anti- inflammatories and benzodiazepines. Adverse effects at label doses are uncommon. Pain on injection can be avoided by refrigerating the vial 6 . Maropitant is not approved for use in puppies younger than 8 weeks of age and kittens under 16 weeks of age. The higher dose for use against motion sickness in puppies is also only approved for puppies 16 weeks or older, this is due to bone marrow hypoplasia being reported in 8-week-old puppies given 6-10mg/kg once daily. Pathophysiology of Emesis Cancer Chemotherapy Opioids Chemoreceptor Trigger Zone (CTZ) (Outside BBB) Dopamine D 2 5HT 3 , Opioids Receptors, substance P Celebral Cortex Smell Sight Thought Anticipatory emesis Vomiting Centre (medulla) Muscarinic, 5HT 3 & Histaminic H 1 , substance P Vestibular Nuclei Motion sickness Chemo and radio therapy Gastroenteritis Pharynx & GIT 5HT 3 receptors, substance P Figure 1: Graphical representation of Pathophysiology of Emesis Issue 03 | JULY 2018 | 29 Muscarinic Histaminic H 1