Percorten-V is an injectable medication used to treat Addison’s disease in dogs. It replaces a specific type of hormone, called a mineralocorticoid, that a dog with Addison’s disease can no longer produce on its own. Without this hormone, the body loses its ability to maintain healthy sodium and potassium levels, which can become life-threatening. Percorten-V corrects that imbalance and is typically given as an injection every 25 days for the rest of the dog’s life.
What Percorten-V Does in the Body
A healthy dog’s adrenal glands produce mineralocorticoids, hormones that tell the kidneys how to handle sodium and potassium. In Addison’s disease (primary hypoadrenocorticism), the adrenal glands are damaged or destroyed, so these hormones disappear. Sodium drops, potassium rises, and the dog can go into crisis.
Percorten-V’s active ingredient steps in to do what those missing hormones would normally do. It increases the rate at which the kidneys reabsorb sodium back into the bloodstream instead of flushing it out in urine. Chloride follows the sodium, so fluid balance improves as well. At the same time, the drug promotes potassium excretion through the kidneys, pulling excess potassium out of the bloodstream and into the urine. The net effect is that sodium comes back up, potassium comes back down, and the dog’s electrolytes stabilize.
One important detail: Percorten-V only replaces the mineralocorticoid side of what the adrenal glands produce. Most dogs with Addison’s disease also need a separate glucocorticoid (a steroid like prednisone) to replace the other category of adrenal hormones. Your vet will typically prescribe both together.
How It’s Given
Percorten-V is an intramuscular injection, meaning it goes into the muscle rather than under the skin. The standard starting dose is 1 mg per pound of body weight, given once every 25 days. Your vet administers the injection at the clinic, so each visit is usually quick.
Care must be taken to avoid accidentally injecting the drug into a vein, which can cause acute collapse and shock. This is one reason the injection is always given by a veterinary professional rather than at home.
A related product called Zycortal contains the same active ingredient but is formulated for subcutaneous injection (under the skin) rather than intramuscular. The two products use different preservatives and surfactants, but the drug itself is identical. Your vet may choose one over the other based on your dog’s comfort or their clinical preference.
What Monitoring Looks Like
After each injection, especially in the early stages of treatment, your vet will want to check your dog’s sodium and potassium levels through a simple blood draw. The American Animal Hospital Association recommends checking electrolytes at two points: 10 to 14 days after the injection, and again at 25 days (right before the next dose is due). The first check shows whether the dose is strong enough. The second reveals whether the drug is lasting long enough to hold electrolytes steady until the next injection.
These results guide dose adjustments. Some dogs do well at the standard starting dose, while others need a higher or lower amount, or a slightly shorter or longer interval between injections. Once your vet finds a stable maintenance dose, monitoring visits may become less frequent, though periodic bloodwork remains part of long-term care.
Possible Side Effects
The most commonly reported side effects are increased thirst and increased urination. These two signs often point to too much glucocorticoid (the prednisone your dog takes alongside Percorten-V), but they can also signal that the Percorten-V dose itself is too high. Either way, a dose adjustment usually resolves it.
Other side effects reported in clinical studies and post-approval monitoring include:
- Lethargy or depression
- Vomiting and diarrhea
- Loss of appetite
- Weakness
- Weight loss or unexpected weight gain (weight gain can signal fluid retention from too much sodium reabsorption)
- Skin and coat changes
- Pain at the injection site, and in rare cases, an injection site abscess
Less common but more serious reactions include facial or muzzle swelling, hives, anemia, and anaphylaxis. These are rare based on post-approval reporting, but they’re worth knowing about so you can recognize them quickly.
Risks of Overdosing or Prolonged High Doses
Because Percorten-V drives sodium retention, too much of it over time can increase blood volume, cause fluid buildup (edema), and even lead to cardiac enlargement. Rapid or excessive weight gain between injections is one of the earliest warning signs that the dose is too high. This is why the regular electrolyte checks matter so much, particularly in the first few months of treatment while the vet dials in the right dose for your dog.
Living With a Dog on Percorten-V
Addison’s disease is a lifelong condition, and Percorten-V is a lifelong treatment. The good news is that most dogs with well-managed Addison’s disease live normal, active lives. The routine settles into a pattern: an injection at the vet’s office roughly once a month, periodic blood draws to confirm electrolytes are in range, and a daily oral steroid at home.
The costs can add up over time since the injections, vet visits, and bloodwork are ongoing. Some owners find it helpful to ask their vet about dose optimization early on, since many dogs can be maintained on lower-than-starting doses once their individual needs become clear. A lower effective dose means less medication per visit, which can reduce both cost and the risk of side effects.