Atipamezole-A Better Antidote to Amitraz?

Amitraz is a pesticide used in dogs for demodicosis treatment and tick control. Intoxication occurs from cutaneous exposure to high concentrations of the pesticide or from accidental oral ingestion. Classic clinical signs in dogs include central nervous system alterations, such as sedation, loss of reflexes, lethargy, and incoordination, as well as bradycardia, hypotension, hypothermia, polyuria, hyperglycemia, emesis, mydriasis, and decrease of intestinal motility. Yohimbine, an α2-adrenergic antagonist, has been used to treat canine amitraz intoxication. This paper compares the responses of dogs to yohimbine with those of atipamezole, a new α2-adrenergic antagonist. Dogs were divided into 3 groups of 10 animals each. Group A received amitraz at a dose of 1 mg/kg IV, group AY received the dose of amitraz plus 0.1 mg/kg yohimbine 30 minutes later, and group AA received the amitraz and 0.2 mg/kg atipamezole 30 minutes later.

Yohimbine reversed all the alterations induced by amitraz but caused significant cardiorespiratory effects, such as tachycardia and tachypnea. Atipamezole was also an effective antagonist for amitraz but had fewer cardiorespiratory effects.

COMMENTARY: Amitraz (Mitaban, Pfizer) is currently unavailable on the market with little knowledge as to when it will be available again. Efforts have been made to use alternative products containing amitraz such as Taktic (Hoechst-Roussel Vet) but there have been several reported cases of toxicity. Atipamezole (Antisedan, Pfizer) has potential as an alternative treatment of amitraz intoxication in dogs.

The comparative efficacy of yohimbine and atipamezole to treat amitraz intoxication in dogs. Andrade SF, Sakate M. VET HUMAN TOXICOL 45:124-127, 2003.

New FDA Fees: Faster Drug Reviews and More R&D Spending

A new program of user fees outlined by the Animal Drug User Fee Act of 2003 authorizes fees by the Food and Drug Administration (FDA) relating to new animal drug applications. The program is similar to the very successful program for human drugs that has been in place for over 10 years.

As passed by the House and Senate on November 7, this legislation allows for the collection from pharmaceutical companies of annual user fees totaling $43 million over 5 years, beginning with $5 million in fiscal year 2004. The fees will enable FDA to hire and train additional scientific reviewers and implement enhanced processes to accelerate and improve the review of new animal drugs to ensure that they are safe and effective for animals as well as for human consumers with respect to animals intended for food consumption.

A faster, more predictable review process is expected to spur more spending and R&D for animal drugs by industry. The legislation must be signed by President Bush to go into effect.