Strongid and Drug Testing

[Trish Dowling <dowling@skyway.usask.ca>]

From: esppatty@juno.com (Patty Lambert)

Can someone clear up a question for me? Are we allowed to compete  a
horse on Strongid-C? I was told a couple of years ago that I would have
to stop giving it a few days before the ride in order to not have any
testable levels. I discontinued it, and at the ride had problems - gut
sounds diminished - ended up pulling at 25, as he wasn't looking very
happy & not enough gut sounds. This was the first and only time he ever
had this or any metabolic problem. Since then, I've not put him back on
Strongid-C. One vet told me the problem was lkiely that I cut him off
cold turkey instead of tapering off the wormer. Anyone out there care to
comment?

Patty in PA 

Ok, I'll stick my neck out on this one. The veterinary pharmacologists are a very small group (there are only 30 of 
us) and I know most the of people involved in drug detection. We are a no drug sport by definition, but this is an 
unenforceable position. So technically, you are not supposed to have any concentration of any drug in your horse 
on competition day. But elimination of drugs from the body is logarithmic, meaning that there is always a fraction 
of the drug left in the body till infinity. So that really means no drug in your horse above a detectable amount. What 
is the detectable amount? Depends on the drug, the individual animal and the ability of the lab to detect the drug. 
What is the reality? The drug testing labs and the sport organizations get together and determine what level of 
Bute, etc that they 1) can find and 2) are going to consider significant. As we are considered a no drug sport, any 
concentration was considered significant. But the methodology can find levels of drugs like Bute that are much 
lower than what is necessary to alter that horse's performance. Now, the AERC has decided to leave the 
interpretation of the significance of the detected amount of drug up to the (correct me if I'm wrong here, someone 
on the Board) Veterinary Committee. That way no one gets penalized for trace amounts of drug. You are no longer 
guilty until proven innocent. If you give your horse Bute two weeks before a ride under veterinary orders for a 
legitimate reason, you won't be automatically busted if they find a trace amount on the day of the ride. So what 
about "drugs" like Strongid C? Reality - it is extremely expensive to do drug detection. There is not an omnipotent 
computer that they put a blood sample into and it spits out the analysis for every drug on the market. (People 
think this - we got a call from a woman who was sure that her boyfriend had poisoned something in her kitchen 
and wanted us to test everything, for every toxin known to mankind. ARRGGHHH! We charge $75 just to look for 
lead in a blood sample.) You have to decide what you are going to look for. So they only look for the drugs that 
have the potential to be abused and alter performance. They are not looking for dewormers, glycosaminoglycans, 
etc. So I use common sense and practice good medicine and mangement on my horses. If I get busted for that, I'll 
find another sport.

The technical vet from Pfizer replied yesterday:
Trisha,
     
     I have reviewed the Strongid C submission and see nothing in the short 
     and long term toxicity profile of the product to explain the 
     experiences related below with regard to endurance horses on Strongid 
     C. I will forward your message to our equine guru Bob Dressler for his 
     opinion. 
     
     It's hard to argue with someone claiming that the signs resolved once 
     the product was stopped. Assuming that the changes described are real 
     I could theorise that stress and strenuous exercise increased 
     absorption predisposing the endurance horse to cholinergic adverse 
     effects at a lower dose than previously regarded as toxic. Of course I 
     may be completely wrong about that. What do you think?
     
     That could possibly explain the abnormal recovery and sudden HR 
     changes noted. Yes? 
     
     I have no explanation for the anemia mentioned - there is no mention 
     of that in  any of the tox studies.
     
     I would have thought that Joe diPietra would know as well as anyone 
     else as he did a lot of the original pyrantel studies.
     
     I'll let you know what I get back from Bob.


Cheers,
Trisha

Trisha Dowling, DVM, MS, Diplomate ACVIM & ACVCP
Associate Professor, Veterinary Clinical Pharmacology
Western College of Veterinary Medicine
Saskatoon, SK S7N 5B4
306-966-7359/FAX 306-966-7376