Principles of Drug Use in Animals

Use of Drugs in Animals

• Basic principles for animal health products were discussed on November 4, 6, and 8, 2024.
• Topics covered included:
  • Overview and broad types of drugs
  • Context for drug use in animals
  • Differences between companion and food animals
  • Drug selection considerations
  • Improper use and treatment failure
  • Adverse reactions
  • Laws and regulations
  • VCPR (Veterinarian-Client-Patient Relationship)
  • Extra-label use

Issues with respect to drugs

• Desire for healthy pets and livestock with good welfare
• Demand for healthy, safe food and environment
• Need to ensure drugs used in people remain effective
• Concerns about drugs in food or environment
• Concerns about bacteria developing resistance to antibiotics
• Loss of effective antibiotics
• Consideration of the effect of drug use on the welfare of animals
• Following existing laws and regulations

Why Study Principles of Drug Use in Animals?

• Drugs can improve animal health and welfare
• Reduce disease in animal populations
• Treat individual animals (pets, food animals)
• Reduce animal distress, pain, and losses
• Provide economic benefit through reduced treatment costs

What is a "Drug"?

• Substance recognized by official pharmacopoeia or formulary
• Intended for use in diagnosis, cure, mitigation, treatment, or prevention of disease
• A substance intended to affect the structure or function of the body
• Includes biological products.

Examples of Categories of Drugs

• Biologicals
• Antimicrobials (e.g., antibiotics)
• Other pharmaceuticals

Biologicals

• Products derived from living organisms, including vaccines, antibody preparations, and hormones.

Antimicrobials

• Broad term for natural or synthetic compounds that kill microorganisms or suppress their growth, including antibiotics, ionophores, antiseptics, and disinfectants

Other Types of Pharmaceuticals used in Animals

• Parasiticides
• Fungicides
• Tranquilizers and anesthetics
• Analgesics (pain medications)
• Hormones
• Cardiovascular drugs
• Chemotherapy drugs
• Vitamins
• Minerals

When We Use Drugs in Animals

• Use drugs in the correct context, considering:
  • Animal's basic preventive care (herd health)
  • Competent diagnosis before prescribing
  • Considering all benefits and risks (animal/disease, human safety, environmental safety)

Treatment and Control of Disease

• Proper treatment requires accurate diagnosis
• Appropriate treatment and changes to management practices, including herd health programs and biosecurity measures.

Food Safety – Balancing Act

• HACCP (Hazard Analysis Critical Control Point) programs for food safety
• Categories of hazards include biological (pathogenic bacteria, viruses, parasites), chemical (drug residues, pesticides), and physical (needles, flies).

Reasons for Drug Use in Livestock (Examples)

• Therapeutic treatment of infections, parasites, pain, inflammation, or deficiencies.
• Preventive measures such as vaccinations to prevent infection
• Treatment or prevention of malnutrition, promotion of growth.
• Use of antibiotics, hormones, and nutrients.

Companion Animals

• Use in human medicine
• Diseases in many organ systems (cardiac, kidney, liver, gastrointestinal, endocrine, behavioral, degenerative)
• Cancers, immune diseases

Livestock

• Economic value of the animal
• Trade domestically and internationally
• Treated as herd or flock
• Consumption as food
• Withdrawal or withholding times

Rational Use of Drugs in Animals

• Improper drug use and failures of therapy
• Adverse effects and toxicity

Considerations When Evaluating a Proposed Course of Treatment

• Minimum information needed for a rational treatment decision
• Explanation to the owner/caretaker of the animal

Therapeutic Goal

• Alter specific pathologic process
• Determine if the drug is absolutely necessary
• Bacterial Infection - use antibiotic to kill bacteria
• Heart Disease - use a drug to decrease or increase heart rate/contraction

Routes of Administration

• Routes available for the drug (IV, IM, subcutaneous, oral, topical)
• Decision basis for the chosen route

Dose, Frequency, Duration

• Dose (mg/kg) within the range of the drug
• Frequency (once/twice/three times daily)
• Duration (how long)

Is this a food animal?

• Drug approval for food animals
• Consideration of withdrawal times

Cost

• Per treatment, considering expected duration of therapy
• Cost compared to animal’s value
• Cost appropriate to seriousness of disease
• Include related clinic costs

Special Precautions

• Considerations based on animal, age, conditions, use, strain, and species
• Contraindications for the drug
• Expected adverse reactions; monitoring and response

Evaluating Results

• Evaluate if the drug is working (physical response, blood tests)
• Determine follow-up procedures (re-examination, diagnostics)

Improper Drug Use

• Consequences such as:
  • Delay of diagnosis
  • Failure to treat a life-threatening but curable disease
  • Prolonged illness
  • Toxicity
  • Development of other disorders
  • Drug residues in food or antibiotic resistance
  • Increased costs

Possible Causes of Treatment Failure

• Wrong diagnosis
• Viral infection misdiagnosed as bacterial
• Multiple problems not recognized
• Right diagnosis with highly virulent pathogen
• Late treatment initiation
• Inaccessible infection
• Resistant bacteria

Possible Causes of Treatment Failure

• Ineffective medicine
• Inaccurate dose
• Other concurrent drugs interfering
• Expired or degraded product
• Resistant bacteria

Adverse Effects and Toxicity

• Many years ago, drug therapies often used ineffective drugs and placebos
• Serious side effects or toxicity still occur in some patients.

Adverse Drug Reactions

• Any adverse change in condition caused by a drug
• Steps to take:
  • Alter or cease treatment
  • Treat symptoms
  • Suggest future treatment with increased risk

Drug Reactions and Toxicities

• Intrinsic drug reactions (dose-related and predictable)
• Idiosyncratic drug reactions (not dose related)
• Allergic responses

Idiosyncratic Reactions

• Not dose-related
• Not predictable, peculiar to the individual
• Associated with drug-specific or patient-specific characteristics or environmental factors

Allergic Reactions

• Not dose-related
• Unrelated to pharmacological effects, but can be severe.

Clinical Case: Bella

• 6-year-old Pomeranian-Chihuahua mix
• Experiencing facial swelling after vaccination
• Treatment with antihistamines, corticosteroids

Use of Drugs in Animals

• Laws, regulations, VCPR
• Extra-label use

General Drug Laws and Regulations

• Federal laws, provincial laws/regulations, veterinary profession bylaws
• Distinguishing between OTC and prescription drugs
• Vet-client-patient relationship (VCPR)

Definitions

• Prescription: Written instructions in accordance with Health Canada
• Generic name: Chemical or common name
• Brand/trade name: E.g., Tylenol (brand name) vs. acetaminophen (generic name).

Federal Legislation for Drugs

• Health Canada regulates the sale of drugs in Canada
• Veterinary Drugs Directorate (VDD)

Health Canada's Veterinary Drug Directorate

• Responsible for licensing veterinary drugs
• Protecting both human and animal health
• Sets standards for human food safety
• Promoting responsible use of drugs for pets and livestock

Federal Legislation regarding Drugs

• Food and Drugs Act
• Licensing, testing, safety
• Includes food, drugs, contraceptives, devices, and cosmetics
• Regulates import, export and transport across provinces
• Requirements related to labeling, sale, and distribution
• Categories (OTC, veterinary prescription, non-prescription).

Controlled Drugs and Substances Act

• Narcotics and other drugs
• Regulations for prescriptions, warnings, documentation.

Non-scheduled (OTC) Drugs

• Low risk, can be bought without a prescription
• Includes pain meds, cold medications, and antihistamines

Since 2018 in Canada

• Antimicrobials medically important for humans are on the prescription list.
• Prescription from a veterinarian needed for important antimicrobials

Provincial Laws (Alberta)

• Pharmacy and drug act, veterinary profession act, animal health act
• Authorized medicine sales regulation

Pharmacy and Drug Act

• Regulates Alberta pharmacist profession, pharmacies, and drug sales

Veterinary Profession Act

• Regulates the veterinary profession.
• Defines qualifications, scopes of practice, registration requirement
• Gives authority to prescribe and dispense animal drugs

Prescription drugs for Veterinary Use

• Available only under a veterinarian's prescription.
• Must adhere to manufacturer's labels
• Subject to withdrawal conditions

Requirements of a Veterinarian-Client-Patient Relationship (VCPR)

• Veterinarian's responsibility for clinical judgment
• Knowledge of animal's health, diagnosis, treatment.
• Sufficient knowledge means vet is acquainted with animal's care
• Client agrees to follow vet's recommendations.
• Vet availability for follow-up and emergencies.

Producers

• Biosecurity, herd-health program, on-farm safety
• Works with vet to ensure VCPR
• Record keeping and animal identification
• Proper disposal of products

Veterinarians

• Diagnosis and treatment planning
• Establish VCPR and may not dispense outside of relationship
• Prescription for drugs and medicated feeds
• Educating producers on relevant information
• Reporting adverse reactions
• Continuing education

Extra-Label Drug Use (ELU)

• Using a pharmaceutical product not in accordance with the label instructions.
• Approved use in other countries does not affect appropriateness for the species or use.
• Use of a drug approved for human's use instead of veterinary use
• Administering the drug in a manner not explicitly stated on the label

CVMA Position Statement

• Extra-Label Drug Use (ELDU) as a strategy for treatment only by licensed veterinarians
• Application under VCPR
• Use in circumstances where an approved product isn't available or suitable.

Examples of ELUs

• Administering drugs to a species with no pre-approved product
• Administering drugs by an unapproved route

Admin of a non-approved dose/frequency

• Common situation due to a single dose/frequency on drug labels.
• Veterinarians may choose different doses/frequencies
• Need additional use in clinical settings.

Admin of a drug for disease not on label

• Common practice, veterinarians with background knowledge may administer drugs for diseases not listed on the label.
• Pharma companies may not test all possible diseases.
• Producers may use this without realizing it as practice.

Why not ban ELU completely?

• Important for state-of-the-art vet medicine
• Significant suffering for animals
• Increased costs for vets
• Limited research on smaller species
• Limited clinical data
• Lack of economic incentive for research

Is there any drug safely usable in all species?

• No single drug is suitable for all species or applications.

Explore the essential principles of drug use in animals, focusing on their health and welfare. This quiz discusses the types of drugs, selection considerations, and applicable laws and regulations. Learn about the differences between companion and food animals while considering the implications of drug use on animal well-being.