New Analgesia Drugs for Dogs
Pain management plays a vital role in veterinary medicine, because veterinarians have a professional obligation to alleviate and manage an animal’s pain, which reduces the animal’s stress, increases their wellbeing, and improves case outcomes. Managing pain and preserving quality of life in small animal medicine are as important as healing illnesses and injuries. Advances in analgesia therapies are helping veterinarians provide improved pain management, and the Food and Drug Administration (FDA) recently approved two new analgesia drugs for dogs.
Firox™
On March 28, 2022, the FDA approved the first generic firocoxib chewable tablet indicated for controlling osteoarthritic pain and inflammation, and postoperative pain and inflammation after soft tissue and orthopedic surgery in dogs. Firox™ is a coxib class non-steroidal anti-inflammatory drug (NSAID) that works by inhibiting the enzyme cyclooxygenase, leading to decreased prostaglandin synthesis that contributes to less pain, fever, and inflammation throughout the body. Firox™, sponsored by Norbrook Laboratories, Ltd., is a generic version of Previcox®, which the FDA first approved on July 21, 2004. The Federal Food, Drug, and Cosmetic Act allows a veterinary drug sponsor to submit an abbreviated application for a generic version of an approved brand name veterinary drug, so long as they can demonstrate that the generic medication is bioequivalent to the approved animal drug. Bioequivalence studies for Firox™ included:
- In vivo study — A study was performed to determine the comparative in vivo blood level bioequivalence for Firox™ and Previcox® in fasted dogs. Forty healthy beagles from 2 to 12 years of age were included in the study, and each dog received 57 mg of either Firox™ or Previcox®, depending on the randomized treatment sequence. The in vivo bioequivalence study demonstrated that the two drugs are bioequivalent in dogs.
- In vitro study — To receive a waiver from the requirement to perform an in vivo bioequivalence study for the generic 227 mg tablet, in vitro dissolution studies were conducted to determine Firox’s™ 57 mg and 227 mg chewable tablet dissolution profiles. Results demonstrated similar dissolution profiles, and a biowaiver for Firox™ 227 mg was granted.
Zenalpha®
On March 30, 2022, the FDA approved Zenalpha®, a medetomidine and vatinoxan hydrochloride injection, for use as a sedative and analgesic in dogs to facilitate clinical examination, clinical procedures, and minor surgical procedures.
Medetomidine is a potent alpha 2 adrenoceptor agonist that inhibits sympathetic neurotransmission inside the central nervous system, and can decrease consciousness, body temperature, and respiratory rate. In the peripheral vasculature, medetomidine acts in the vascular smooth muscle to induce vasoconstriction and hypertension, which decreases heart rate and cardiac output. Other potential effects include piloerection, depressed gastrointestinal function, diuresis, and hyperglycemia. Medetomidine has previously received FDA approval.
Vatinoxan is an alpha 2 adrenoceptor antagonist that selectively acts on the peripheral nervous system, attenuating medetomidine’s negative effects. Vatinoxan does not alter medetomidine’s central nervous system effects, but the drug does improve cardiovascular function, which increases medetomidine’s clearance, reducing the duration of sedation and analgesia. This is the first FDA approval for vatinoxan, giving Zenalpha®, sponsored by Vetcare Oy, marketing exclusivity for five years. Safety and effectiveness studies performed on Zenalpha® included:
- Field effectiveness study — Zenalpha®’s effectiveness was evaluated in 223 client-owned dogs who presented to the veterinary clinic for a planned examination or procedure. Six veterinary clinics in New York, Maryland, Illinois, Colorado, Pennsylvania, and Louisiana were included in the study. Zenalpha® was administered to 110 dogs, and dexmedetomidine was administered to 113 dogs. To be considered effective, Zenalpha® had to be similar or better than dexmedetomidine at allowing the veterinarian to complete the planned procedure, and superior to dexmedetomidine at causing less severe cardiovascular adverse effects. Results demonstrated that Zenalpha® was effective at providing sedation and analgesia in dogs to facilitate clinical examinations, clinical procedures, and minor surgical procedures when administered at the labeled dose. Dogs who received Zenalpha® had less severe heart rate and body temperature decreases compared with dogs who received dexmedetomidine, and also reached sedation onset and recovered more quickly.
- Atipamezole reversal study — A laboratory study was conducted in eight beagles to determine if atipamezole could effectively reverse Zenalpha’s® sedative and cardiovascular effects. Atipazemole administration resulted in sedation reversal in 10 to 20 minutes, and a return to baseline heart rate and blood pressure values in 20 to 30 minutes.
- Target animal safety study — A laboratory study was conducted in 32 beagles to evaluate Zenalpha’s® safety when administered intravenously once a day for four days. Results demonstrated that this regimen did not produce systemic toxicity and had an acceptable safety margin. The study supported the safe use of Zenalpha® as a canine sedative when used according to the label.
Pain management is paramount to good veterinary care, and these new analgesia drugs for dogs will provide additional tools for veterinarians when performing examinations and minor procedures, and determining treatment protocols for painful dogs.
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