The Cascade (“Off-label drugs”)

The cascade is a set of legislation that vets are legally obliged to follow. It is made to ensure that vets use drugs that are licensed for the species of animal and the indication for which they are prescribed whenever possible, while providing the flexibility to allow use of drugs that are not licensed when no licensed drugs are available. This is to ensure safety for the animal, the owner, the vet administering the drug and for the environment, while 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 licensed in other species or people.

The cascade is as follows:

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”). There are five steps that should be followed to identify appropriate drugs that can be prescribed under the cascade if there is no licensed drug available:

1. Veterinary medicine with a Marketing Authorisation valid in GB or UK wide for indicated species and condition
2. Veterinary medicine with a Marketing Authorisation valid in NI for indicated species and condition, in accordance with a Special Import Certificate granted by the VMD
3. Veterinary medicine with a Marketing Authorisation valid in GB, NI or UK wide for a different species or condition. For products not authorised in GB or UK wide, a Special Import Certificate from the VMD is required
4. Human medicine with a Marketing Authorisation valid in GB, NI or UK wide OR an authorised veterinary medicine from outside of the UK. For products not authorised in GB or UK wide, a Special Import Certificate from the VMD is required; in the case of horses intended to enter the human food chain, the medicine must be authorised for a food-producing species
5. Extemptoraneous preparation prepared by a vet, pharmacist or person holding an appropriate Manufacturer's Authorisation, located in the UK

Exception: In exceptional circumstances, a human medicine may be imported form outside the UK. For products not authorised in GB or UK wide, a Special Import Certificate form the VMD is required

Use of “off-label” drugs:

The use of off-label drugs may be necessary when licensed 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. They must inform the owner that an off licence medication is being used and will ask the owner to sign a form agreeing to this use. Often 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.

KEY POINTS:

• Medicines prescribed under the cascade cannot be used in animals intended for human consumption - if you cannot confirm that part II of Section II (part II Section IX in pre-2016 passports) is signed to exclude the horse from the human food chain, the owner must be informed in writing that the horse cannot enter the human food chain
• Informed consent if required when using any medicine off licence / off-label under the prescribing cascade (specific consent needs to be obtained for each unorthorised medicine used)
• Although consent can be given verbally, the RCVS expect that consent is given in writing. When the client is not available to give written consent, contemporaneous records of verbal consent must be recorded
• It is the responsibility of the prescribing vet to obtain consent
• It is pracitce policy that we do not permit lifelong consent - if a specific ongoing condition requires unauthorised medince for life in a specific animal, new consent should be obtained annually