Unit 1

Question 1

Four rules to live by for safe drug usage

Answer 1

Rule #1: all drugs are poisons
Rule #2: no drug is a silver bullet
Rule #3: all doses are guesses
Rule #4: complacency kills

Question 2

Chemical name of a drug is

Answer 2

Gives the molecular formula of the drug: never changes
Already listed on the drug label

Question 3

Generic or non-proprietary name is

Answer 3

Common name
Refers to the active pharmaceutical ingredient
Generic name never changes
Human, veterinary, different countries
Does not indicate the dose formate or formulation
Starts with “small case”

Question 4

Trade name (proprietary) is

Answer 4

Capitalized followed by a @ (registered) or ™ (trademarked) symbol
Proprietary names that are licensed by a specific drug manufacturer
Refers to a specific drug that has been formulated in a specific manner
Names will change by country

Question 5

Generic equivalents is

Answer 5

Aka “generics”
Do not appear until the original patent on the licensed trade name drug has expired
Contains the same active drug as the original licensed drug (same as the original tradename product)
But may not work exactly the same due non-medical components that may affect the kinetics/dynamics of the drug in the body

Question 6

Sources of drug info

Answer 6

Label/package insert
Compendium
Veterinary drug formularies

Question 7

On label drug use is and advantages

Answer 7

Using a drug according to the directions on the drug label without deviation
Advantages
Drug is more likely to be effective: known outcome
Decreases risk of side effects
In the event of adverse effects, the manufacturer will stand behind the product
Professional safety net in the event of adverse effects occurring
Known withdrawal time (WT) for food animals
Always the preferred method of using a drug

Question 8

Extra label drug use is

Answer 8

(ELDU)
Aka “Off-label” drug use
“The use of a drug product in a manner that is not consistent with what is indicated on the label, package insert or product monograph of any drug product approved by health canada”

Question 9

What is ELDU

Answer 9

Alteration of any of the following form what is described and approved on the drug label is considered extra-label use
Use in a species not listed
Use for an indication (disease or condition) not listed
Use of a different dosage
Use of different frequency of administration
Use of different route of administration
Eg. giving injectable brute orally to a horse. Most drugs in cats or exotics!

Question 10

Responsibilities of EDLU

Answer 10

Always requires a prescription and valid VCPR
Responsibility for all aspects, including safety, adverse reactions, withdrawal times lie with the prescribing vet
Applies to all prescription drugs and OTC medications used off-label
Not permitted for insecticides, pesticides, biologicals (including vaccines)
Best to Avoid ELDU in ALL food producing animals due to questionable WT

Question 11

Compounding is

Answer 11

Is considered ELDU
“Animal drug compounding is the process of combining, mixing, or altering ingredients to create a medication tailored to the needs of an individual animal or a small group of animals, and these drugs can play a critical role in veterinary medicine” FDA May 1, 2023
E.g. Having a pharmacist compound a drug into a dosage from to ease administration e.g. methimazole topical gel for cats
Mixing penicillin with dexamethasone into ointment in your clinic to make “scratches ointment” for a horse

Question 12

Dosage def is

Answer 12

The mass of drug needed per unit of weight of the animal (10mg/kg)
Refers to any animal

Question 13

Dosage form is

Answer 13

Physical form of the drug - tablet, liquid, suspensions, ointment etc.

Question 14

Tablet dosage form

Answer 14

Only break if scored
Considered ELDU is split more than intended

Question 15

Capsule/gel-caps dosage form

Answer 15

Powdered drugs placed in a gelatin
capsule
Opening capsules or dividing capsules is considered ELDU

Question 16

Substained-release dosage form is

Answer 16

Tablets or capsules with a special exterior coating that decreases the rate of dissolution
Disrupting the coating is considered ELDU

Question 17

Suspension dosage form

Answer 17

Particles of drug in a liquid; shake before EACH use
Never give suspensions by IV route

Question 18

Ointments/creams dosage form

Answer 18

Includes drugs with lots of systemic side effects or those that do not have good oral absorption

Question 19

Dosage regimen is

Answer 19

Refers to the complete information needed
Specific amount of drug: number and frequency of administration over a certain amount of time
Mass of drug (most commonly expressed as mg)
Route of dosing
Frequency (aka dose interval)
Duration

Question 20

Therapeutic range and drug toxicity is determined by

Answer 20

Remember= all drugs are poisons!
Selection, amount or method of administration are all involved in determining whether a drug cures or kills.
Once a drug is selected
The concentration of drug inside the animal is what determines whether a drug will be beneficial or toxic

Question 21

Drug toxicity is

Answer 21

All drugs have the potential to eb toxins
Outright overdose, relative overdose, side effects, accidental exposure, drug interactions, incorrect treatment

Question 22

Acute adverse effects of drug toxicity is

Answer 22

Show up immediately; often no further damage once drug is removed
Effects on the CV/ respiratory system/ muscles/ GI/ nervous/ endocrine/ reproductive systems

Question 23

Chronic adverse effects of drug toxicity

Answer 23

May not be revealed for years or generations
Decreased reproduction, teratogenicity, cancer
Long-term liver damage

Question 24

Lethal dose is

Answer 24

*every drug has the ability to cause death
LD50 (Median lethal dose)
Measure of toxicity
Definition: dose of a drug that kills 50% of the animals that receive it
Drugs with a high LD50 are safer than drugs with a low LD50
Chemicals with LD50 values less than 300 mg/kg are considered moderately toxic and
Those with LD50 values between 1 000 and 5 000mg’kg are considered slightly toxic
Alters with species, age, health status of patient

Question 25

Effective dose is

Answer 25

The purpose of giving a drug is to produce a therapeutic effect. The amount of drug required to reach this therapeutic effect is called an effective dose
ED50 (Median effective dose)
Amount of drug (mg/kg) required to produce a desired effect in 50% of animals that receive it

Question 26

ED50 is

Answer 26

May be different for each indication
Ex
ED50 is higher for septic peritonitis than for skin infection
Lower doses of pred are used to decrease inflammation; at higher dose, it is immunosuppressive
A low dose of pentobarbital can be used as anticonvulsant; a higher dose and produce unconsciousness; twice that dose will produce euthanasia
Individual patients may require a slightly higher or lower dose

Question 27

Therapeutic index is

Answer 27

A measure of drug safety
Is the difference between the effective dose and the lethal dose
TI =LD50/ED50

Question 28

Examples of TI

Answer 28

If TI is high (»1), the drug is safe to use
If TI is low (>1) the drug is less safe to use
If TI is 1, treatment or death are equally likely to occur
If TI is <1, the indication for the drug is death

Question 29

Why is TI important

Answer 29

We assume that drugs with a high TI also have lower risks of other adverse side effects
Always provided on the drug label
Testing is on average, healthy patient

Question 30

LD50 and TI will be lower if:

Answer 30

Very sick
Very old
Very young
If used in combination with other drugs

Question 31

Practically speaking what does ED50, LD50, and TI do

Answer 31

ED50- tells us how much drug to use to treat
LD50- tell us how much drug is needed to kill
TI- gives an idea of how safe the drug is to use

Question 32

How are most drugs administered

Answer 32

Most drugs are administered systemically
Even those drugs that are administered locally (i.e., directly to the lesion) may eventually absorb (through at lower levels) into the bloodstream

Question 33

Why is drug in plasma important

Answer 33

For a drug to work, it must get to the target tissue via the plasma
Must me certain concentration of drug in plasma to have an effect
Once in the plasma, drugs can go to any tissue (not just the target tissue) and could possible have adverse effects

Question 34

Therapeutic range is

Answer 34

Concentration of drug in the blood that will provide a desired therapeutic effect, with the least adverse effects
Dosage goal

Question 35

Toxic range is

Answer 35

Higher than desired concentration of drug in the blood
May be therapeutic, but adverse side effects will occur

Question 36

Subtherapeutic range is

Answer 36

Lower than desired concentration of drug in blood
The drug has no beneficial effects, but potential exists for side effects
When referring to antimicrobial use, there is high risk of creating drug resistance
Words of wisdom
More is not better. Less is better

Question 37

Maximum effective concentration (MEC) is

Answer 37

Border between concentrations that are beneficial and concentration when adverse effects are first noted
Highest desired drug concentration; if higher, adverse side effects will occur

Question 38

Minimum effective concentration (MEC) is

Answer 38

Lowest drug concentration in blood to obtain the desired effect
Below the MEC, the drug has no beneficial effects (but, may still have potential side effects)

Question 39

Dosage and the therapeutic range

Answer 39

The goal of any dosage is to maintain the concentration of drug in the therapeutic range
Smaller, more frequent doses are more likely to stay in the therapeutic range
Less frequency dosing requires large doses that are more likely to exceed the maximum effective concentration; there is also a greater chance of dropping below the minimum effective concentration between doses

Question 40

Narrow Therapeutic range is

Answer 40

Narrow therapeutic range= drugs that have a maximum effective dose and the minimal effective dose very close to each other
Narrow therapeutic range = narrow therapeutic index
The dose that produces the minimal beneficial effect is not that far from the dose that produces toxicity
Should not be dosed in such a way that causes wide swings between the peak and the through concentrations

Question 41

Loading dose and maintenance dose

Answer 41

Initial larger dose “loads” the bucket (body)
Smaller “maintenance” dose matches the bodies rate of elimination to maintain body levels

Question 42

Total daily dose

Answer 42

Combined amount of drug (mass) times the number of doses administered in a given day

Question 43

Peak concntration

Answer 43

Highest drug concentration

Question 44

Trough concnetration

Answer 44

Lowest drug concnetration

Question 45

2 main categories of routes of drug delivery

Answer 45

Parateneral
-Para- beside; enteron- intestines
-Not by the intestines
Non-parenteral
-Not “not by the intestines”; aka “by the intestines”
-Includes those drugs administered topically
-Applied to a particular place on or in the body. Most often body surface of mucous membranes

Question 46

Intravenous drug administration is good for and why not put these SQ and IM

Answer 46

Safe administration site of a drug that would otherwise be irritating or painful if injected IM or SQ
Some drugs accidentally injected extravascular can cause extreme tissue inflammation, necrosis and sloughing of the skin over injection site

Question 47

Rapid IV bolus is

Answer 47

Single dose given over approx 30 sec; CPR drugs can be faster
Fastest onset of action - immediate
All the drug enters the plasma
Higher initial plasma levels of drug results in fastest therapeutic effect
Highest peak drug concentration = higher risk
Shorter duration of activity

Question 48

Slow IV bolus is

Answer 48

Single dose given 10-20 min
Onset of action not as rapid as IV bolus
Slower time to peak concentration and lower peak concentration
Still immediate
All the drug enters the plasma
Decreases peak concentration

Question 49

Constant rate infusion is

Answer 49

A very small dose of drug given at very short intervals
Can be for short or extended period (i.e., days)
Example: micrograms per sec
BEST for maintaining therapeutic range with minimal deviation in blood plasma concentration
Amount in equals the amount metabolized in the same period of time

Question 50

Intramuscular dosage is

Answer 50

Muscle has great blood supply
In general: relatively rapid onset of action
2nd fastest absorption and onset of action
Also, longer duration of effect than IV routes
Close to 100% of drug absorbed
% drug absorbed and rate of absorption can be affected by drug formulation
Repositories or depot preparations delay drug release
Some drugs should never go IM or SQ as will cause severe inflammation or tissue necrosis

Question 51

Intradermal dosage is

Answer 51

Into the dermis
Skin has excellent blood supply
Very similar curve to Im delivery
Fairly rapid absorption and onset of action; almost 100% of drug is absorbed (depending on formulation)
Limited volume of drug can be delivered and excess volumes are painful

Question 52

How does heat affect intradermal drug absorption

Answer 52

Heat → vasodilation→ speeds up absorption; increases risk of toxicity

Question 53

Subcutaneous drug administration is

Answer 53

Under the skin, including the SQ fat
Slower absorption and onset of action than IV/IM/ID routes due to lower vascularity
Even slower if injected into fat layer
Fat is not well vascularized
Also, lipophilic drugs have delayed absorption as fat will act as a sink and bind drug
Rate of absorption affected by temp similar to ID
Heat → fast
Cold→ slow
Can give larger volumes IV/ID

Question 54

Intraperitoneal drug administration is good for

Answer 54

Slower absorption than SQ
Can give very large volumes
Drug is absorbed via the mesenteric vessels and can ultimately end up in the liver (in which case, shares properties of non-parenteral routes)

Question 55

Intra-arterial and intra-cardiac drug administration is good for

Answer 55

Very rapid onset and highest peak plasma concentration in all tissues, especially the heart and brain
Very high risk of toxicity- AVOID

Question 56

Non-parenteral drug administration includes

Answer 56

Includes
Oral, sublingual and recta;
Absorption rates, onset of action and % of drug absorbed all depend on which of the above rates is used

Question 57

Advantages of non-parenteral drug administration

Answer 57

Lowest cost
Easier routes of delivery- owner can manage
Can give large volumes of PO/rectal

Question 58

PO is and how does the drug break down

Answer 58

Drugs are given by mouth and ingested. Must travel the digestive tract during which can be digested/broken down by digestive enzymes in saliva, the intestines or stomach acid
Stay in the intestines and act locally (i.e.,are not absorbed and act on the lumen of the digestive tract
Ex: ant-acids, pre/probiotics/soothers
Absorbed into the plasma

Question 59

Limitations of per os

Answer 59

Long onset of action
There is always some loss of drug
Stomach acid, digestive enzymes in saliva and intestines, microbial digestion
Must be formulated in a way to withstand digestion/degradation
Drug is absorbed may be metabolized in the liver ( aka “1st pass effect”)
Side effects: GI upset as many drugs are acids themselves or disturb GI flora
Doesn’t work well in ruminants or if GI Dz
Calves are treated more like monogastric spp

Question 60

Sublingual drug administration is good for

Answer 60

The oral mucosa in some animals is easily crossed by small molecules (esp cats and neonates)
Most permeable areas are under the tongue (sublingual) and buccal pouch (cheek pouch)
Drug is placed in these areas → rapidly crosses mucosa→ very vascular
Rate of absorption, onset of action are similar to IM/ID routes

Question 61

Disadvantages of sublingual drug administration

Answer 61

Some drug is lost to enzymes in saliva or swallowing
Any drug that is swallowed is not absorbed
Does avoid the “1st pass effect” and intestinal digestion

Question 62

Rectal drug administration is good for

Answer 62

Preferred method for unconscious or seizing patients
Bypasses all digestive functions
Drug is absorbed with the rectal mucosa

Question 63

Disadvantages of rectal drug admin

Answer 63

Inconsistent absorption

Question 64

Topical drug delivery is preferred for

Answer 64

Administration of a drug directly to the target tissue
Preferred for
Drugs with severe systemic side effects
Drugs with poor absorption and/or distribution; hard time getting to the intended target tissue
Drugs with a high cost
Target tissues that are easily accessible (skin wounds, ear canal, eyes)

Question 65

Examples of topical drug delivery

Answer 65

Topicals: ointments, creams, eye and ear drops
**Just because a drug is applied to the surface of the skin, does not mean it is a local delivery. Many anti-parasitics are applied to the skin and absorbed into the bloodstream in order to have an effect
Aerosols
Nebulizers, metered dose inhalers (puffers)

Question 66

Advantages of topical drug administration

Answer 66

Faster onset of action
Peak concentration of drug in the target tissue is reached much faster
Increases concentration of drug at the target tissue
Specifically decreases systemic side effects
There is still some risk of systemic toxicity as drug could be absorbed- less is absorbed
Depends on the drug and the patient
Can use a lower dose of drug, thus lowering cost

Question 67

What to do for drug toxicity

Answer 67

Veterinary staff must act quickly to counteract any problems caused by drug treatment
Tell someone!
Remove drug if possible- may induce vomiting
Get antidote/reversal
Enhance elimination (diuresis, ventilate)
Dilute/constrict; cool/heat
Treat symptomatically, nursing care
Know your drugs, always have drug labels available
Report adverse reactions!