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Off-Label Medications and the veterinary Cascade
What is the Veterinary Cascade?
The cascade is a set of legislation that veterinary surgeons are legally obliged to follow. Its purpose is to ensure that vets use drugs that are licensed for the species of animal and the indication for which they are prescribed whenever possible, whilst providing the flexibility to allow use of other drugs when no licensed products are available. This is to ensure safety for both the animal and the owner or person administering the drug, whilst at the same time allowing sick animals to be treated in the most appropriate way when they become ill. Licensed drugs will have undergone rigorous tests to ensure that they are safe and effective in treating specific diseases in specific species. Unfortunately, there are relatively few drugs specifically licensed for horses, which means that we need to use other drugs authorised in other species or for humans.
How does the veterinary surgeon decide what drug to use?
Veterinary surgeons must use medication licensed for the species (e.g. horse or donkey) and indication (i.e. illness or medical condition) for which they are prescribed. If no such medication is available, the cascade is followed (this is called ‘off-label use’). In descending order of priority the vet may use:
- A veterinary medicine licensed in the UK for that indication in another species, or one that is licensed for a different indication in the same species.
- Either - i) A medicine authorised in the UK for human use, or - ii) A medicine licensed in the EU for use in any animal species.
- A medicine made up at the time on a one-off basis by a veterinary surgeon, a pharmacist or a person holding an appropriate manufacturer’s authorisation.
- In exceptional circumstances, medicines may be imported from outside of Europe via the Veterinary Medicines Directorate’s import scheme.
Use of ‘off-label’ drugs
The use of off label drugs may be necessary when authorised medicines are not available, but there are certain risks involved. Drugs can be metabolised differently in different species, so although it may be safe in one species it can be harmful in another, or the dose required may be different. The same goes for use of human drugs in animals. It is down to the prescribing veterinary surgeon to use their clinical knowledge and experience to weigh up the risk versus the benefit of the treatment in each case. RVC Equine vets will inform an owner that an off-label medication is being used and will ask the owner to sign a form agreeing to this use. In the majority of cases the drug will have been used previously and will have shown to be safe and effective in a clinical setting, even though it has not been subjected to the licensing protocols. It is very expensive and labour intensive to get a drug tested and approved for each species and indication, so unless a large market exists for the particular drug it may not become licensed. It is however, important to use the licensed drugs whenever possible, as this is not only the best way to ensure safe and effective treatment, but also provide funds to further the research and allow more drugs to become tested and licensed for animal use.
Use of the cascade in food-producing animals
Under EU law, horses are classified as food animals so any medications given must be permissible to enter the human food chain or a suitable withdrawal period before slaughter for human consumption must be observed. This applies certain restrictions on the drugs available to use. However, if a horse has been signed out of the human food chain in its passport then it can be treated as a companion animal and these restrictions no longer apply. A horse can be permanently excluded from the human food chain by signing Section IX of the passport (Section II of some newer passports).
For more information on the veterinary cascade see GOV.UK: The Cascade: Prescribing unauthorised medicines
If you have any concerns over the medication your veterinary surgeon has prescribed for your horse, please call RVC Equine on 01707 666297.
Antimicrobial resistance is an emerging clinical problem that is recognised internationally as one of the largest threats to human and animal health.
RVC Equine is joining efforts with major health and veterinary organisations to try and limit the development of resistance so that effective antimicrobials can be retained for use in clinical practice.
Antibiotic drugs are essential for the treatment of bacterial diseases in humans and animals. To ensure they remain effective all healthcare professionals are working together to limit the further spread of antibiotic resistance. This occurs when bacteria mutate their genetic code so antibiotics can no longer kill them. Some bacteria can then pass this acquired resistance to other bacteria either in the same animal, in other animals or even in humans.
- Every time an antibiotic is used there is the potential for bacteria to become resistant to that drug.
- Every time an antibiotic is used that is not essential the risk of resistance outweighs any potential benefit of the drugs.
- It is vital that antibiotics are used very carefully to ensure they are available to help our horses for as long as possible.
Why is resistance such a problem?
Once bacteria develop resistance they will no longer be controlled by that drug and all drugs in the same category will be ineffective. There have been no new types of antibiotic in decades, just a slow improvement of the existing ones. Similarly there are no new options in the pipeline to replace the existing drugs.
What are we doing about it?
RVC Equine supports the British Equine Veterinary Association’s responsible antibiotic use guidelines – “Protect ME”. This means we have identified antibiotics categorised as critically important and pledged to PROTECT them. As such we are playing an important role in the prevention of further antibiotic resistance. By targeting the use of antibiotics carefully, and particularly by not using them wherever possible, we can all help to make sure they continue to work and are effective when they are really needed.
What can I do to help?
Horses rarely carry diseases that affect humans and similarly humans rarely infect horses. However there are some important exceptions, including MRSA and Salmonella. Not only can be transferred from your horse to you, but also from you to your horse, or from one horse, via you, to another horse. Thorough handwashing is important to reduce contamination and prevent the development of diseases in your horse or yourself that will reduce the need to use antibiotics.
When can we avoid antibiotics completely?
Antibiotics do not work for the treatment of viral infections so should not be used. In many bacterial infections, otherwise healthy horses are able to mount an effective immune response and cure themselves, without the need for antibiotics. If your horse has an infection your veterinary surgeon will decide whether antibiotics are likely to be beneficial. If they are not required you should not expect your veterinary surgeon to dispense them. They are acting in the best interests of your horse to ensure that these drugs work when they are needed.
The following examples explain why antibiotics may not be needed in the treatment of some common diseases:
- Strangles: Although this is a highly emotive condition, antibiotics are rarely needed in the treatment of strangles. The abscesses represent your horse’s natural effective response to the bacteria. Antibiotics will not improve the recovery from this infection.
- Foot abscess: Again, the abscess represents your horse’s effective response to the infection. Once these are drained, and provided you follow your vet’s advice, your horse will improve without the need for antibiotics.
- Wounds: Every cut triggers a response from your horse which removes damaged tissue and infection, allowing the wound to heal. The majority of wounds heal without the need for antibiotics, although those that involve deeper structures, especially the joints, are more serious and may need intensive treatment with antibiotics.
- Diarrhoea: Most cases of diarrhoea in horses are not caused by bacteria; indeed your horse’s intestines are full of ‘friendly bacteria’ that can be killed by antibiotics, and this itself can in fact cause diarrhoea. In the majority of cases your horse will recover without antibiotics, but they may require replacement of fluids, either as drinking water, or in some cases directly into the vein.
- Foaling: Although foals are born with no natural immunity, they can acquire antibodies from the mare’s first milk (colostrum). If they are healthy there is no benefit from treating them with antibiotics.
- Viral diseases: Viral diseases, causing a temperature, coughing, and sometimes a nasal discharge, cannot be treated with antibiotics. Like the common cold, these usually improve in 1 to 2 days, and antibiotics will not speed up that recovery.
Please respect your veterinary surgeons decision to PROTECT antibiotics and only use them when they are needed.
Prescriptions are available from the RVC Equine Practice vets.
You can obtain Category V (meaning issued by a veterinarian) Prescription Only Medicines (POM-V) medicines from your veterinary surgeon OR ask for a prescription and obtain these medicines from another veterinary surgeon or pharmacy.
Your veterinary surgeon may prescribe POM-V medication only for animals under their care.
A prescription may not be appropriate if your animal is an inpatient or if immediate treatment is necessary.
You will be informed, on request, of the price of any medicine that may be dispensed for your animal.
The general policy of this practice is to re-assess an animal requiring repeat prescriptions every six months, but this may vary with individual circumstances.
Further information on the prices of medicines are available on request.