Prescribing and dispensing: The cascade

What are features of authorized veterinary medicines?

Granted by VMD

Relatively costly process

Pharmaceutical companies have a list of requirements

What do pharmaceutical need to do in order to have medicines approved as authorized veterinary medicines?

Demonstrate quality, safety, and efficacy

Consider potential risks to environment, animals, operators, and consumers

Produce a Summary of Product Characteristics (SPC)

What are potential disadvantages of unauthorized medicines?

May not be of consistent quality, may not be safe and effective in animals, may pose a threat to operator, may pose a risk to consumers, may pose a threat to the environment

In general, we as veterinarians should

Use an authorized product and use it according to the SPC

What are possible exemptions to the guidance of “use approved medications?”

Medicinal products used in scientific research, exceptional circumstances, immunological products in imported/exported animals, “the Cascade”

Define the cascade

A mechanism to allow us to prescribe unauthorized medicines to our patients

What must you keep in mind when using the cascade?

Balance benefit: risk

Ensure decisions are evidence-based

Comply with routine veterinary practice

What are examples of situations where the cascade might be applied?

Authorized medicine is contraindicated

Authorized medicine has proven ineffective, Authorized medicine is not available due to supply issue

An owner would have difficulty administering the authorized product

There is no authorized medicine

What can the cascade NOT be justified for?

Economic grounds

How informed do owners need to be if you are using drugs via the cascade?

Fully informed consent should be provided, clients should be made aware of the intended use of unauthorized medicines and given a clear indication of potential side effects (their consent should be obtained in writing).

Who can prescribe a medicine for an animal using the cascade?

Only a veterinary surgeon

Who can authorize vet medicine for use under the cascade, human medicines, or extemporaneously prepared medicines against a prescription from a vet?

A pharmacist or veterinary surgeon

Who can dispense an authorized vet medicine for use under the cascade against a prescription from a vet?

Any Suitably Qualified Person, provided they have the relevant qualification for that species

What is the logic behind the cascade for vets in GB?

Proceed stepwise, progress to the next step if there is no suitable vet medicine in your country

Cascade for vets in GB: Step 1

Vet medicine authorized in NI for use in the same species and condition

Cascade for vets in GB: Step 2

Vet medicine authorized in GB, NI, or UK for use in a different species (if a food-producing animal must be another food-producing species) for the same condition

OR

Vet medicine authorized in GB, NI, or UK for use in same species with a different condition

Cascade for vets in GB: Step 3

Human medicine authorized in GB, NI, or UK

OR

Vet medicine authorized outside the UK for use in same species and condition

Cascade for vets in GB: Step 4

An extemporaneous preparation prepared by a vet, pharmacist, or person holding a Manufacturer’s authorization in the UK

What additional requirements exist when considering the cascade in food producing animals?

Extra regulations to protect consumer, active substance must have an MRL (Maximum Residue Limit) in a food producing species, vet must specify withdrawal periods, vet must keep additional records

What is the maximum residue limit (MRL)?

Safe concentration of medicines in animal-derived food product, typically expressed in microgram/kg, can be established or provisional

When is a maximum residue limit not needed?

Active principles of biological origin intended to produce active or passive immunity

GB MRL Register: Allowed substances contain

Lists of substances with an MRL either has been established, is being established, or does not need to be established

GB MRL Register: Prohibited Substances contain

Lists of substances in which an MRL cannot be established or any residue, at any level, is hazardous to human health

What is a withdrawal period?

The time during which an animal food product cannot enter the food chain

What is the aim of a withdarawl period?

Allow for residue level in product to fall below MRL

Minimum statutory withdrawal period: In GB, Eggs …

1.5x longest Withdrawal period for eggs in SPC for any species

14 days if not authorized in animal producing eggs for human consumption

Minimum statutory withdrawal period: In GB, Milk…

1.5x longest withdrawal period in SPC for any species

1 day if the product has zero hour withdrawal period

7 days if not authorized in animals producing milk for human consumption

Minimum statutory withdrawal period: In GB, meat and offal from poultry and farmed game birds…

1.5 x longest withdrawal Period in SPC for meat and offal

1 day if zero hour withdrawal period

28 days if not authorized for meat-producing species

Minimum statutory withdrawal period: In GB, fish…

1.5x longest withdrawal period in SPC for any aquatic species

25 degree days if highest WP for any species is zero

50x longest WP in SPC for food producing terrestrial animal

Withdrawal periods for imported products, you must consider

SPC in the country of origin, then apply the specified WP

If you use the product in a different way (species, route, dose, etc) then apply the minimum statutory WP or the product wp, whichever is longer

When handling unauthorized medicines in food animals, vets must 

Keep records of the following for a minimum of 5 years:

Date of exam, name and address of owner, Animal id and number treated, result of clinical assessment, trade name of product, batch number, name and quantity of active substance, dose administered and/or supplied, duration of treatment, withdrawal period

Horses as food animals features

EU legislation classifies the horse as a food animal

UK almost all are signed out of the food chain

Small minority are not and for these the food animal cascade must be applied

Equine passports features

It is an offence to keep a horse without a passport (applicable for all equidae

Passport must remian with the horse at all times!

Before prescribing for a horse, the first time the horse is seen be sure to

Check microchip and cross check with passport , ask owner to sign horse out of food chain, record status in clinical records

If a horse is declared “not for human consumption” then you should

Treat as for any companion, non-food animal

Follow the normal always use a licensed product first, justify off-label or unlicensed use

If a horse is declared “for human consumption” then you should

Follow food animal cascade, medicines which cannot be administered, record medicines given in passport

What are the essential substances list?

Additional substances that can be used in horses intended for human consumption

BUT a minimum of 6 month withdrawal period must be applied

What treatment considerations are there if there is no passport for the horse?

Is it necessary to treat immediately? Treat the horse as ‘intended for human consumption’

In an emergency, if health/welfare of horse is at risk treatment with a substance not allowed in food animals is permitted

Features of phenylbutazone for treatment in horses

Cannot be used in a horse intended for human consumption, no MRL set, not on the allowed list in GB MRL register, not on the essential list

What must you consider when treating competition horses?

Substances may be prohibited from use in horses competing (seek guidance from the affiliation website