Managing Hyperkalemic Periodic Paralysis

At the 2006 American Association of Equine Practitioners Convention, Dr. Sharon Spier spoke about HYPP.

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At the 2006 American Association of Equine Practitioners (AAEP) Annual Convention, Sharon Spier, DVM, Dipl. ACVIM, PhD, gave a talk called "Hyperkalemic Periodic Paralysis: 14 Years Later," referring the identification in 1992 of Quarter Horse sire Impressive as the sole bloodline carrying the mutant gene that causes HYPP. What has changed since then?

Although the American Quarter Horse Association (AQHA) announced foals born in 2007 or later that test homozygous for HYPP (H/H) will not be eligible for registration, it is currently estimated that 4% of Quarter Horses are affected. This number has not dropped, even with DNA testing now widely available and mandatory since 1998 for foals descended from Impressive.

That means there are still a lot of horses out there that must be managed with diet, exercise and medication. Here are the current recommendations:

  • Avoid high potassium feeds such as alfalfa hay, brome hay, soybean meal, sugar and beet molasses, and electrolyte and kelp-based supplements (plain salt is okay);
  • Use low potassium feeds like later cuts of timothy or Bermuda grass hay, along with beet pulp, and grains such as oats, corn, wheat, and barley;
  • Feed multiple small meals throughout the day so that no one meal exceeds 33 grams of potassium;
  • Allow the horse turnout time, especially onto grass pasture;
  • Be aware of trigger factors such as fasting or abrupt changes in diet, anesthesia or heavy sedation, trailer rides, stress, and others;
  • Medicate with oral acetazolamide to remove excess potassium from the body.

For more information, or to order a testing kit, visit

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Written by:

Lydia Gray, DVM, is Medical Director and Staff Veterinarian for SmartPak Equine. She was previously the executive director of the Hooved Animal Humane Society in Woodstock, IL, and an Owner Education Director for the American Association of Equine Practitioners.

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