Cascade and human generics
What is it?
The Cascade is a long-standing legal flexibility providing a rational balance between the legislative requirement for veterinary surgeons to prescribe and use authorised veterinary medicines where they are available, and the need for professional freedom to prescribe other products where they are not. It is intended to increase the range of medicines available for veterinary use.
Why is it important to use authorised medicines?
Animal species may have many physiological differences from humans and from each other. As a result they each may react differently to medicines. The authorisation system for veterinary medicines requires a product to have proven quality and effectiveness and, most importantly, safety for the animal, the user (vet, farmer, pet owner etc.), the environment and, for food animals, the consumer of animal produce. This assurance has to be provided for each species and each indication on the label.
In addition, animal medicines containing the same active ingredient as human medicines may be formulated differently in terms of method of manufacture and excipients. A different formulation can have an impact on, for example, the absorption of a medicine, in that, a medicine developed to be absorbed in the human gut may behave differently in a cat due to a difference in gastric volume or emptying time, thereby affecting the amount of active substance available in solution in the gut and ultimately, the bioavailability. Further to this, the safety of the excipients may not have been established for a particular veterinary target species. Authorised veterinary 'generic' medicines will have been compared to pioneer veterinary products which have been tested in the authorised species but this is not the case for human 'generic' products. Therefore, this legal requirement to use veterinary medicines over human medicines is in the interests of animal health and welfare; using a product that is not authorised for animals may increase the risk of harm to them, and this is reflected in the order of the decision making tree when prescribing under the cascade.
As well as being in the interests of the patient, selecting veterinary products supports the veterinary pharmaceutical industry to develop more veterinary products. These are developed specifically for the named target species, ensuring appropriate dosing is established and that product literature contains relevant and up to date evidence-based information to ensure the safe and effective use of these medicines in animals.
However, there are exceptional circumstances where the use of an unauthorised (e.g. human or vet special) product may be justifiable when a veterinary product is authorised. In these instances, a patient with a chronic condition, receiving long-term or life-long treatment may have been stabilised on an unauthorised product prior to a veterinary product being authorised. If the responsible veterinary surgeon considers, on the basis of their professional clinical judgement, that changing a patient's treatment under these circumstances could destabilise them, it may be justifiable to continue with the unauthorised product in that patient. New cases would need to be treated with the veterinary alternative. Otherwise, prescribing a human product where a veterinary product is authorised and available is a criminal offence and is contrary to the RCVS Guide to Professional Conduct.
Vets remain entirely responsible for the treatment of animals under their care; use of a medicine under the cascade should be capable of being supported by clear auditable clinical evidence to justify the vet's decision.
What do vets need to do to comply with the cascade?
If there is no medicine authorised in the UK for a specific condition, the veterinary surgeon responsible for treating the animal(s) may, in order to mitigate unacceptable suffering, treat the animal(s) in accordance with the following sequence:
1a veterinary medicine authorised in the UK for use in another animal species or for a different condition in the same species; or, if there is no such product that is suitable;
ia medicine authorised in the UK for human use, or
iiin accordance with an import certificate from VMD, a veterinary medicine from another Member State; or, if there is no such product that is suitable;
3a medicine prepared extemporaneously, by a vet, pharmacist or a person holding an appropriate manufacturer’s authorisation.
For food-producing animals the following additional conditions apply:
•the treatment in any particular case is restricted to animals on a single holding
•any medicine imported from another Member State must be authorised for use in a food-producing species in that Member State
•the pharmacologically active substances contained in the medicine must have MRLs
•the prescribing vet must specify an appropriate withdrawal period – statutory minima are in the Regulations; however, some substances may require considerably longer withdrawal periods to ensure consumer safety. If you are unsure about the appropriate withdrawal period you should set, please refer to the VMD guidance (accessible via the website) or contact the VMD.
•the prescribing vet must keep specified records.
A medicine prescribed in accordance with the cascade may be administered by the prescribing vet or by a person acting under their direction. Responsibility for the prescription and use of the medicine remains with the prescribing veterinary surgeon. Where veterinary surgeons write prescription using the 'cascade', the prescription should contain a statement advising that this is the case.
The VMD supports and encourages the responsible use of antibiotics. Responsible antibiotic use under the cascade requires vets to take into consideration not only the most appropriate active substance(s) but factors such as appropriate formulation, posology, the current pattern of resistance in the locality and an awareness of how to reduce selection pressure. The VMD considers that it is justified, on a case by case basis, to prescribe an antibiotic on the cascade in the interests of minimising development of resistance, i.e. prescription of a narrow spectrum antibiotic on the cascade over a broad spectrum antibiotic that has a specific indication for that condition. More detailed guidance can be found under: Responsible antibiotic use under the prescribing cascade at www.gov.uk
For further information, please see the VMD’s veterinary medicines guidance: The Cascade: Prescribing unauthorised medicines, available from www.gov.uk
Animals need medicines to help prevent disease and to help treat them if they do fall ill. All species deserve the benefit of medicinal products which have been specifically developed and authorised for their treatment. The cascade ensures this happens wherever possible, but also gives flexibility for veterinary surgeons to use their clinical judgement to prescribe a medicine where no veterinary authorised medicine exists.