There are several medications used to treat Addison’s disease. The first type acts as a mineralocorticoid and replaces aldosterone – the hormone responsible for maintaining electrolyte levels. It is replaced with either the injectable Percorten-V™ (desoxycorticosterone pivalate or DOCP) or an oral medication called Florinef ™ (fludrocortisone acetate). For dogs that have atypical or secondary Addison’s neither of these medications are used because the production of aldosterone isn’t
In addition to aldosterone, the cortisol, or glucocorticoids, normally secreted by the adrenals must also be replaced. This is typically done with an oral form of prednisone or hydrocortisone. During a crisis, the dog may receive an injection of dexamethasone, a potent and fast-acting glucocorticoid. The dog may be started initially on high doses of prednisone to facilitate a return to health. On an on-going basis, the glucocorticoid dose can be reduced and in some cases eliminated except on an as-needed basis. With atypical and secondary Addison’s the glucocorticoid is the only medication given.
Primary Addison's disease is treated by replacing the mineralocorticoid, Aldosterone, with either injectable Percorten-V or oral doses of Florinef. These medications help maintain the balance of the electrolytes Sodium (Na) and Potassium (K)
Percorten-V™ also known as
desoxycorticosterone pivalate or DOCP is the injectable form of medication used to treat primary Addisons.
Percorten-V is the brand name for desoxycorticosterone pivalate. It is an injectable medication with only mineralocorticoid activity. It does not have any glucocorticoid activity. The dose recommended by Novartis, the manufacturer, is 0.75 – 1.0 mgs per one lbs. of bodyweight, given every 21 – 30 days. There are 25 mgs in each ml (or cc) of the medication.
A 50-pound dog would receive between 37.5 – 50 mgs or 1.5 – 2.0 mls. Some dogs are adequately maintained on lower doses, while some dogs require lower doses to minimize rare side effects. Percorten-V is available only through a licensed veterinarian, although some veterinary pharmacies may carry the medication.
Florinef ™ or fludrocortisone acetate
is the pill form of medication used to treat primary Addisons. It can also be purchased in compounded form.
Florinef is the brand name for fludrocortisone acetate. This medication is also available in its generic form, fludrocortisone acetate, from compounding pharmacists. It is primarily a mineralocorticoid, but also has some glucocorticoid activity. The starting dose recommended by the Merck Veterinary Manual is 0.05 – 0.1 mgs per 10 lbs of bodyweight. Some dogs require significantly higher doses to maintain normal electrolytes.
The dose may be divided and given twice per day or given all at once, usually in the morning. A 50-pound dog would take between 0.25 and 0.5 mgs to start. The brand name Florinef tablets may be purchased directly from your vet or from a pharmacy. Some people find it more cost effective and efficient to have the proper dose of the medication prepared by a compounding pharmacist in capsule, liquid, or chewable form.
The adrenal glands produce cortisol, a glucocorticoid. It is the hormone measured by the ACTH Stimulation test used to diagnose Addison’s disease.
All dogs with Addison’s require the supplementation of glucocorticoids in times of stress. Many need glucocorticoids on a more regular basis, particularly those on DOCP. Dogs with atypical or secondary Addison’s only take glucocorticoids.
The most common glucocorticoids are prednisone, hydrocortisone and dexamethasone. There are additional glucocorticoids such as prednisolone and methylprednisolone. The Merck Veterinary manual recommends a prednisone dose of 0.1 – 0.2 mgs/lb. per day. This is equivalent to 0.4 – 0.8 mgs/lb. per day of hydrocortisone.
Glucocorticoids, such as prednisone, should be given to an Addison's dog in times of stress and in some on a more regular basis.
However, some dogs show symptoms of excess glucocorticoids on these doses. These problems may include excessive drinking and urination, increased appetite, recurring infections, elevated liver enzymes, panting, restlessness and even behavioral changes. Because these dogs will be on medications for the rest of their lives, it is important to fine-tune the dosages to maximize benefits, while minimizing unwanted side effects. If you are working to reduce your dogs dose of glucocorticoids, be sure to work with your vet and lower the amount slowly.
Determining what constitutes stress for your dog, when additional glucocorticoids are necessary, is very individual. Like people, dogs find different situations stressful. Stress can be in many forms, both good and bad, from physical to emotional. For some dogs a trip to the vet requires extra medication, while for others it could be houseguests or extra active playtime. Knowing your dog’s triggers is crucial. It is essential to monitor the dog closely and be prepared to give extra medication when the need arises.
Addison’s disease is diagnosed through a blood test called the ACTH Stimulation or Response test. This test is typically only done once to diagnose the condition. To perform the ACTH stimulation test, an initial blood sample is drawn and the cortisol level is measured. The dog is injected with a synthetic form of the pituitary hormone ACTH that tells the adrenals to produce cortisol. After an hour, blood is drawn again, and the cortisol level measured. Resting cortisol should range from 1-4 μg/dl in the average dog, and should be significantly higher, in the range of 6-20 μg/dl, post-stimulation. If resting cortisol is low and the dog has no or a low response to the stimulation, the diagnosis is Addison’s disease. Be aware that some glucocorticoids, such as prednisone, can affect the results of the ACTH test, while dexamethasone does not.
Electrolyte ratio is determined by dividing the "NA" number by the
145÷4.5 = 32
At diagnosis, your dog will probably have what’s referred to as a Super Chem or Chem Panel and CBC (Complete Blood Count) to look at other important blood values. The results from these blood tests help to determine if organs such as the kidneys, liver and pancreas are functioning properly, as well as if any signs of infection are present. A complete blood test should be completed every 6 months to one year for a dog with Addison’s disease.
There are two blood test results that are of particularly interest in Addison’s disease. They are Sodium (Na) and Potassium (K). The hormone Aldosterone regulates these electrolytes. In primary Addison’s disease, the adrenal glands don’t produce (enough) Aldosterone, so it must be replaced with Florinef or DOCP. This is information that you and your vet will use to monitor the effectiveness of the mineralocorticoid (DOCP or fludrocortisone). The electrolytes are checked frequently at the beginning to determine correct medication levels.
Normal ranges for these values may vary based on the lab and equipment used. Typically, the normal level for Sodium is between 139 to 154 mEq/L and Potassium should be between 3.6 to 5.5 mEq/L. In addition to looking at these values, it can be helpful to look at the ratio between the two. This number is derived by dividing K into Na and should be between 27 and 40. For example, a dog with a Na level of 145 and a K level of 4.5 would have a ratio of 32. A dog in an Addisonian crisis will typically have a low Na level, elevated K and low ratio. It is important to learn at what levels your dog feels his best. Continue Reading »»
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