A supplemental source of Chondroitin, Glucosamine HCl and Hyaluronic Acid.

FlexSyn™ can produce a visible impact on performance within 24 hours. FlexSyn™ offers a unique delivery system to supply Chondroitin Sulfate, Glucosamine HCl and Hyaluronic Acid, providing a potent supply of fast-acting equine joint support ingredients. Scroll down for complete information.

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Average rating:  
 9 reviews
by Julie Cook DVM on FlexSyn™
In my observation, FlexSyn works

The results I've observed from FlexSyn in my practice have surpassed expectations. Quality of movement seems to greatly improve with use.

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Product Summary



Each FlexSyn™ suppository delivers a potent and readily bio-available supply of Chondroitin Sulfate, Glucosamine HCl and Hyaluronic Acid making it ideal for both pre-event and maintenance applications.


  • Users report FlexSyn™ effects begin within 12 hours with full effects within 24 hours.
  • Effects are cumulative with repeated administration.
  • Ideal for pre-event use or maintenance for high-level training.
  • Contains no prohibited substances.

*This formula has not been scientifically tested or approved in a blinded study and we make no function claims as to its use to treat any condition.


What is FlexSyn?

What is FlexSyn™?


FlexSyn™ Joint suppositories offer a simple all natural alternative for systemic joint support. The highly potent FlexSyn™ formula utilizes a combination of Chondroitin Sulfate, Glucosamine HCL and Hyaluronic Acid contained in a carrier made of a proprietary blend of plant and fruit butters, cellulose, combined with ingredients to facilitate rapid absorption through the digestive mucosa.


Frequently Asked Questions


Why a suppository? Suppositories have been a widely used but little discussed means in human and veterinary medicine for delivering a variety of ingredients efficiently and easily. The elimination of the undesirable destructive effects of the digestive process and the ease of absorption through the large colon have been shown in studies to allow the actives to quickly enter the bloodstream intact. In addition, the effect of the liver which sequesters and eliminates much of the Chondroitin Sulfate, Glucosamine HCL and Hyaluronic Acid when fed to the horse in current products, is bypassed by the colon’s return blood supply. Risks inherent in IM and IV injections are avoided with no loss of comparable efficacy. The efficiency of suppository even compared to injection is quite favorable. These features make suppository delivery ideal for these joint supplement ingredients.


How quickly does it work? Anecdotal reports indicate that within 18 to 24 hours of first administration users see visible evidence of benefit of supplementation like reduction in joint effusion, improved range of motion and general improved performance. The reported speed of action and improved performance suggests it is a preferred choice for pre-event joint and comfort support.*


How long do the effects of FlexSyn™ last? Users report that they see benefits of a single supplementation persist for 4 to 5 days.*


Is there a loading period for FlexSyn™? While a single dose seems to provide noticeable benefit for 4 or 5 days, users tell us that administering a single dose 4 days apart for 2 to 3 administrations provides a baseline. Users then give 1 dose every 7 to 10 days, with added doses used as a pre-performance boost. In high performing situations, a daily dose for 4 consecutive days is also reported to provide outstanding results, with the maintenance follow up of 1 dose per week offering effective maintenance.


How do I store FlexSyn™? FlexSyn™ should be stored at room temperature, with care taken to refrigerate if there is a chance of seeing temperatures over 80 degrees.


My FlexSyn™ was in 90 degree temperatures and is a little soft to my touch. What do I do? No worries! Simply pop the FlexSyn™ packages into a refrigerator for an hour or two and it will reform. Heat will not damage the actives.


What are the ingredients in FlexSyn™ that make it work? FlexSyn™ contains high quality Chondroitin Sulfate, Glucosamine HCL and Hyaluronic Acid, described as proteoglycans and glycosaminoglycans. GAGs are large molecules found in the joint fluid. Administration of these substances is known to be anti inflammatory and benefit the joint metabolism of horses. There are all sorts of Proteoglycan and GAG formulations used orally, IM, IV and IA in joint injections, which are known to aid joint function to various degrees. These ingredients are the gold standard of natural joint health management. What makes FlexSyn™ special is its unique delivery and enhanced absorption technology which allows safe, efficient administration of a large volume of ingredient.


Can I give 2 FlexSyn™ suppositories at a time for better effect? Some users have reported increased effect when dosing with two suppositories. However, some also mention that the horse may also display more energy because he feels so much better.


What will it cost me to maintain my horse on FlexSyn™? Most people are buying the multi dose 6 pack or the economical 30 pack. You can supplement your horse to a beneficial level using 1 dose a week for under $100.00, or $3.25 per day. Of course, each horse is unique in his joint issues and performance regimen, and costs can vary as his response stabilizes.


Are there studies on FlexSyn™ to prove its effectiveness? FlexSyn™ simply offers a means of supplementing the horse’s natural level of ingredients found naturally within the joint capsule. Custom Veterinary Specialties has done no scientific studies on FlexSyn™ to document its particular efficacy and therefore we make no function claims as to its ability to treat or cure any condition.


*Note: There are no scientific absorption or blood level studies for FlexSyn™.


Ingredients & How To Use



Active Ingredients: Chondroitin Sulfate, Glucosamine HCL and Hyaluronic Acid.


Inactive Ingredients: A proprietary blend of plant and fruit butters, cellulose.




Directions: Click here to visit the manufacturer website for complete instructions.



Field Testing

Field Testing

During the development process, FlexSyn™ was field tested and is highly recommended by:

Steffen and Shannon Peters
Ian Millar and Millar Brooke Farm
Nick Haness
Jen Bauersachs
Shane Sweetnam
Lainie DeBoer
Shannon Dueck
Randy Wilson
David Belford and Chris Payne
Jim and Ellen Toon
Leah Patipa, DVM
Tim Ober, DVM
Christa Baldwin
Adrienne Lyle
Quentin Judge
Lauren Sammis
Sam Berry
Kelly and Rick Christy
Hunter Holloway
Jen Bliss
Jane Ehrhart
Kenny and Ashley Lakins
Bob & Anita Janssen Performance Horses
Bryan McNabb, DVM



Rules & Regulations

No Prohibited Substances


As leaders in the management and preparation of top performance horses, we create the most effective formulas while avoiding all prohibited substances.


See FEICleanSport, USEF or AQHA Guidelines to learn more.