Addison's Disease- A Guide for changing from Florinef to Zycortal for UK owners

Started by Lovemedogs, April 25, 2016, 03:35:39 PM

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  Guidance for the owners of dogs with Addison's disease in making the transition from
Florinef to Zycortal and prednisone (or its equivalent)

This document has been written to guide owners of dogs with Addison's disease through the

transition from Florinef to Zycortal.   

1) Introduction: Why the change ?

Florinef is a drug which has both mineralacorticoid and glucocorticoid activity. It replaces

both the aldosterone and cortisol that a dog with Typical Addison's can no longer make.

Licensed as a drug for humans, it has also been used for dogs as there has been no dog

specific drug alternative until now, with the launch of  Zycortal. Production of Florinef was

discontinued at the end of February 2016. (Fludrocortisone acetate, which has replaced

Florinef, is being produced but at a much higher cost to dog owners)

Zycortal is produced by Dechra UK and was first registered to them in 2014, with a license

running until 2024. It is an injectable drug which has only mineralacorticoid activity. It

replaces only the aldosterone our Adogs can no longer produce, hence when making the

change over to Zycortal, it is important to remember to give a small daily dose of

glucocorticoid suchas prednisolone.

Zycortal was launched in the UK at the BSAVA congress in Birmingham in April 2016, with

sessions being run about Addison's disease, helping to raise awareness of this disease. It is

a drug specifically for the management of Addison's disease in dogs and due to the Cascade

system in the UK, must be prescribed ahead of a human drug (e.g. Florinef ) to treat the

same disease.   

Percorten (DOCP) which has the same active substance as Zycortal (desoxycortone

pivalate) has been used successfully in managing Addison's in other parts of the world for

many years now and the experience of owners using this drug for their dogs is now being

used to aid owners transitioning to Zycortal from Florinef. There will be no need to apply for

a special licence to use Zycortal as people who have been importing Percorten into the UK

have had to do. In addition current UK Percorten users may decide to switch to Zycortal

which will be cheaper for them. 

2) How does Zycortal work ?

Zycortal is a 25mg/ml prolonged-release suspension for injection for dogs. Its aim is to

maintain balance of the electrolytes whereas Florinef balanced the electrolytes as well as

provided a cortisol replacement to deal with stress. The Zycortal product information states

giving an initial starting dose of 2.2 mg / kg, testing the electrolytes firstly at 10 days, then

again at around 25 days in order to determine the next dose. After this first 'cycle' it is only

necessary to check the lytes just prior to giving the next dose. When you first start using

Zycortal, you will need to continue to give the normal dose of florinef for 24 hours after the

first injection, before stopping it. The day after the first injection, once you stop the florinef,

you will then start to give the required dose of pred each morning.

One of the most important things about using Zycortal effectively and efficiently is to make

sure the lytes results are used to determine the next dose. You are aiming to have well

balanced lytes throughout the cycle just as you did each day with Florinef. Basically, if the K

is below the middle of its reference range at the end of the cycle, then you know too high a

dose has been given last time, so you need to reduce it. Always remember that Zycortal

raises the Na and lowers the K. 

Zycortal does not suddenly stop working, so if you missed giving a dose by a day or so, the

Zycortal will still be working 

3) Does my dog need a daily dose of prednisone ( or its equivalent) and if so how much ?

All dogs having Zycortal will need a daily dose of glucocorticoid to replace the cortisol the

adrenal glands are no longer making and this is one of the noted bonuses of using Zycortal

rather than Florinef as you will now be able to control the amount of glucocorticoid your dog

gets. The glucocorticoids most likely to be prescribed are  prednisone or prednisolone,

though there may be other options (see the chart in Ref 2). Initially as you are transitioning

from Florinef to Zycortal, you need to take into account the amount of glucocorticoid within

the Florinef. Each 0.1 mg Florinef has the glucocorticoid activity equivalent to 0.25 mg pred.

As an example, if your dog is taking 0.8mg Florinef daily, they are taking the equivalent of

2mg prednisolone - so to calculate the starting dose of pred, for each 0.1 mg Florinef your

dog is currently taking you will need to multiply that by 0.25. This is only the starting dose

and over time you will be able to taper that down according to the clinical signs of your dog

until you find the best lowest dose for your dog.   

4) Will my vet let me give the injections myself at home ?

Giving injections at home to our dogs is not something all vets are familiar with in the UK.

However, a precedent has been set by owners of dogs with diabetes, who have to give

insulin injections every day. This is something you need to be comfortable with and have the

discussion with your vet about. Some practices are likely to be much happier about this than

others, some practices also do not charge if a vet nurse gives the injection rather than a vet.

Note it has to be stored at a temperature below 30 deg C and above freezing. It must not be

kept in a fridge. 

5) What happens if I don't need a whole vial of Zycortal at one go ?

Zycortal comes in vials of 4 ml / 100mg. At present this is the only sized vial. The product

has a shelf life of 3 years from production but once opened, the in-use shelf life is  4 months.

It is very likely though, that once you find the best lowest dose for your dog, it can last more

than 4 injections. Only time will tell if it will last for a longer period as the Percorten does.

Initially, if you take your dog to the vet for the injection and your vet practice has more than

one dog using Zycortal and it is being stored stored correctly, it may work out cheaper to be   charged by the ml rather than by the vial, especially for owners of smaller dogs. This would

avoid wastage, so do ask your vet if this is an option. 

6) Where can I buy Zycortal myself ?

Vets will order Zycortal for you unless you have a different arrangement.  You can buy

Zycortal online from internet pharmacies such as or and this is

likely to be a cheaper option than from your vet, but you will need a prescription from your

vet to do this so make sure you figure this into your costs. At the time of writing this, Viovet

were selling a 4 ml vial for £54.21. 

7) What problems might I encounter

Zycortal is a new drug to the vets in the UK and Europe and hence the vets here are not au

fait with using it and nor will most of them be familiar with the Low Dose Protocol research

study carried out for Percorten (see Ref 5), so the first challenge will be in persuading your

vet to dose according to the lytes and not according to the weight going forwards and indeed

the product information does state clearly in cases of hypokalaemia (low potassium),

hypernatremia (high sodium) or a ratio > 32, to lower the dose of Zycortal or extend the time

between injections. However, experience of people using Percorten with their dogs, shows a

clear preference to lowering the dose rather than extending the time between doses in order

to maintain a more consistent balance of the lytes throughout the cycle and in doing so,

avoid highs and lows which is very important in order to keep a dog feeling well all of the


In a clinical trial of Zycortal, very common adverse reactions were noted as polydipsia

(excessive thirst) and polyuria (excessive urination) but these are very likely to be avoided if

the dose of both the Zycortal and the pred (or its equivalent) are optimised for your dog and

the best lowest dose of each found.

Some vets are concerned that once Zycortal is in the system, you cannot take it out so if the

wrong dose was given, what happens ? Well if a lot too much Zycortal was given, your dog

might display symptoms of hypokalaemia (low potassium) or hypernatremia (high sodium)

and if too little were given the opposite - hyperkalaemia (high potassium) and /or

hyponatremia (low sodium) could occur. If the latter were to occur it can easily be rectified by

giving the next dose earlier and adjusting the amount given and should the former occur, 

your dog should be treated symptomatically and the next dose adjusted as needs. It does

emphasise the need to make sure your vet determines the dose according to the lytes

results of your dog as each dog is different.     


  8) What should I do now ?

 Familiarise yourself with the facts about Zycortal. 

 Arrange an appointment with your vet to discuss a plan going forward, make sure

it takes place well before you finish your last Florinef. Have your questions ready!

 Go armed with knowledge, even take a copy of the Percorten low dose protocol

with you but be prepared for your vet to not feel comfortable using it at this stage.

It should however, give your vet food for thought once they have more

experience in using Zycortal.

 Ask your vet questions: 

a.    will the vet agree to dosing according to the lytes

b.   Will the vet support you giving the injections at home (if that is what you wish

to do) ? 

c.  Will the cost of giving the injection be cheaper if a vet nurse gives it instead of

the vet ?

d.  Will your vet either price match internet prices of Zycortal or give you a

prescription to buy your own ? 

e.  How will they decide what dose of pred (or its equivalent) to prescribe for your

dog ? 

For many people, this is a worrying period of travelling into the unknown, but it is also a time

for  embracing the change in the medication for your dog, comfortable in the knowledge that

this is a UK produced drug which most, if not all dogs with Typical Addison's will be changing

over to, in the coming weeks and which is essentially the same drug, Percorten (DOCP),

that has been used successfully across other parts of the world for many, many years.

Zycortal will enable your dog to continue to live a good happy life.   

Lastly, remember the adage  "There are no problems, only solutions".     


1) EMA CVMP Assessment report for Zycortal -

2) Chart comparing the relative activity of steroids - prednisone equivalent 0.25 mg steroid activity in each 0.1 mg Florinef - also showing other alternatives to prednisone

3) Noah's Compendium - a valuable resource of drugs in the UK including data sheets

4) Zycortal Freedom of Information Summary Feb 2016

5) Percorten Low dose protocol  abstract from Wiley

6) Everything you need to know about Zycortal including the Summary for the public

7) Summary of Zycortal product information  for vets which includes the information found on the product insert

8) Viovet - Zycortal product information and where to buy Zycortal from online     

Pam Johnson -  April 2016

Please note that I am not a vet, but I have been helping out on Addison's support groups for over 18

years, having had my own standard poodle with Addison's disease who thrived for 12 years on

Florinef and had he still been here today I would have been in the same position as yourself,

changing over to Zycortal. If you have any feedback on your experience with Zycortal, please get in

touch at