Transcript Principles and Methods of Drug Administration

CHAPTER 3
L. VanValkenburg, RVT, BAS
Safe Drug Use
 All drugs are
.
 Veterinarian and RVT are accountable for safe drug
administration
 Know components of drug order and question anything
that is not complete, is unclear, or does not make sense.
 Verbal drug orders should be documented ASAP.
 When preparing and administering meds:
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Gather supplies first! 
Clean hands, clean supplies, etc.
Well-lit work area with minimal distractions
The Six “Rights” of Proper Drug
Administration
Right Drug
Right Dose
Right Time
Right Route & Technique
Right Patient
Right Documentation
The Right Drug
 “The right drug” means the patient
received the drug that was
prescribed.
 When filling a prescription or
preparing to administer a drug, read
label on the container 3 times!
 Never give a medication from a
container that is unlabeled
 It is important to understand why
the patient is receiving the drug
 Convenia vs. Cerenia
 Prednisone vs. Prednisolone
The Right Dose
 The right dose is the dose
prescribed for a particular patient
 DVMs and RVTs must calculate each
drug dose accurately.
 Before calculating a drug dose, an
estimate of the answer based on
prior knowledge should
be predicted.
 When in doubt, have the dose
recalculated by another DVM or
RVT.
The Right Time
 The right time is the time at which the prescribed
dose should be administered
 Daily drug doses are given at specific times during
the day to keep plasma levels within desirable
concentrations.
 Do you know what SID, BID, TID, and QID mean?
 What about q24H, q12H, q8H, and q6H?
 PRN?
The Right Route and Technique
 The right route is the
proper route of
administration, so that the
patient takes the whole
dose at one time
 Drugs should also be
administered at the
appropriate site in order
to obtain the desired
effect.
 Some routes of
administration are not
feasible for some animals.
The Right Patient
 The right patient means the RVT or DVM
makes certain that the medication is given
to the proper patient
 If patient is in a cage check the cage card
and ID band.
 If the patient is in the exam room, identify
the patient by name.
 When dispensing medication, read the
patient’s name to the owner to ensure the
right animal gets the right medication.
The Right Documentation
 The right documentation requires the person
administering the drugs must immediately
record the appropriate information about the
drug given
• Name of drug
• Dosage administered
• Time and date administered
• The route and site of
administration
• Patient response
• DVM signature or initials
The Right Documentation
 The right documentation is a legal and safety
obligation
 “If it was not documented, it was not done.”
 Legally, controlled substances must also be recorded
in a drug log.
 It should also be documented if an owner refuses
drug treatment for his/her animal including the
reason for refusal
Informed Consent
 Without the client’s consent, the
medication cannot be given!
 Clients refuse because of:
 Lack of knowledge
 Misconceptions
 Past problems with drug
 Inability to ‘cure’ patient
 Inability to medicate pet
themselves
 Financial limitations
Our Therapeutic Goal is to:
Achieve drug concentrations at the site of action (target tissue)…
that are sufficiently high enough to produce the intended effect…
without producing adverse drug reactions.
Too little
Just right
Too much
Drug Concentrations in the Plasma
50
40
Drug
Concentration in 30
Plasma (Cp)
But what’s missing here
that is needed for this
info to be of any use?
20
mcg/mL
10
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Time since administration of drug
(hours)
Drug Concentrations in the Plasma
50
Toxic
Concentrations
40
Drug
Concentration in 30
Plasma (Cp)
Therapeutic Concentrations
(Therapeutic Range)
20
mcg/mL
10
Subtherapeutic
Concentrations
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
Time since administration of drug
(hours)
Therapeutic Range
 The therapeutic range of a drug is the drug concentration
in the body that produces the desired effect in the animal
with minimal or no signs of toxicity.
 Three major drug factors keep drugs in their therapeutic
range:
 Route of administration
 Drug dose
 Dosage interval
Therapeutic Range
 Other factors that play a role in getting and keeping drugs
within the therapeutic range include:
 Drug properties
 Health and physiology of the animal
 Maintaining drugs within range involves maintaining a balance
among:
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Rate of drug entry into body
Absorption of drug
Distribution of drug
Metabolism of drug
Excretion of drug
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YOU WILL LEARN MORE ABOUT THESE THINGS IN THE NEXT CHAPTER 
Routes of Administration
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Oral (PO) (Non-parenteral)
Sublingual
Via feeding tube
Topical
Transdermal
Intranasal
Inhalation
 Nebulized or volatilized
 Rectal (PR)
 Aural
 Topical ophthalmic
 Parenteral routes:
 Intradermal (ID)
 Subcutaneous (SC or SQ)
 Intramuscular (IM)
 Intravascular/intravenous (IV)
 Intraosseous/Intramedullary
 Intraperitoneal (IP)
 Intra-arterial (IA)***
 Intra-articular
 Epidural/subdural/intrathecal
 Intracardiac (IC)
 Intramammary
Routes of Administration
 Parenteral drugs are given by a route other than the
GI tract
 Nonparenteral drugs are given through the GI tract
(orally)
 Factors that affect the route of drug administration
include:
 Drug factors
 Patient factors
Drug Factors
 Some drugs cause one effect when given parenterally and
another effect when given non-parenterally.
 magnesium sulfate causes muscle relaxation when given IV and
diarrhea when given orally
 Some drugs are insoluble in water and can be given IM but
cannot be injected IV – Always be aware of label!
 Some drugs are destroyed by stomach acid and cannot be
given orally.
 Some injectable drugs must be given very slowly; while others
must be given in a bolus.
 Cost and availability of drug must also be considered.
Patient Factors
 Animals that are actively
cannot absorb drugs given orally.
 Critically patients need to get
therapeutic levels of drug into their
bodies
.
 The animal’s temperament
must be considered.
 Can/will the owner medicate their
animal at
properly with the
medication as prescribed?
Other Factors to Consider
 Is restraint going to be an issue?
 Are systemic effects expected or is just a
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local effect preferred?
What is your time frame?
Does this medication require that special
precautions be followed during
administration (i.e. gloves, mask)?
Potential side effects?
What is the most convenient route of
administration for the owner?
Parenteral Administration
Designed by Francis Rynd (1801-1861), this instrument was used for deep injections.
It is made of steel with an ivory handle, and was manufactured by Weiss.
Rynd, an Irish physician, invented the hollow needle in 1844.
Dr Wood first injected a patient
with morphine in 1853.
His wife became the first IV
morphine addict.
The first recorded fatality
from a
hypodermic-syringe
induced overdose was
Dr Wood's wife.
History: Lagniappe
Bevel
Anatomy of a
Syringe
Needle
Cap
Needle
hub
Luer-lock
tip
Barrel
Rubber
stopper
Scale
Plunger
Flange
Thumb rest
Comparison of Common Parenteral
Routes of Drug Administration
Intramuscular
90°
Subcutaneous
45°
Intravenous
25°
Intradermal
10°–15°
Epidermis
Dermis
Subcutaneous tissue
Muscle
Parenteral Drug Forms
 Sterilized solutions
 Prepackaged syringes with needles
 Powders that must be reconstituted with a sterile diluent
 Vials (single or multi-dose)
 Ampules
Intravenous (IV)
onset of action,
initial body levels of
drug, and
duration of activity
 Drug concentration is predictable.
 Injection techniques include: BOLUS administration,
INTERMITTENT therapy, and INFUSION of fluid
 In most cases, IV drugs should be given slowly
 Remove air bubbles!
 Usually water soluble drugs; rarely emulsions
 Avoid perivascular injection of IV drugs.
Intramuscular (IM)
 RELATIVELY
onset of action and
duration of
activity than IV drugs
 Blood levels reliable and typically significant in ~30 minutes.
 Absorption rate depends on drug formulation
 Repository or depot preparations delay absorption
 Ex: Procaine penicillin G and Depo-Medrol (methylprednisolone)
 IM drugs can be in aqueous solutions or suspensions.
 Solutions are clear liquids that contain one or more solvents and one or
more solutes.
 Suspensions are liquid preparations that contain solid drug particles
suspended in a suitable medium.
Subcutaneous (SC)
onset of action and
duration of
activity than IV and IM drugs;
onset than
PO admin.
 Blood levels LESS RELIABLE than IV or IM
 Absorption rate affected by the vehicle in the
preparation and temperature.
 Larger amounts of solutions can be given SQ
 Cannot use irritating solutions!
 Pellets can also be implanted into the
subcutaneous space
Intramammary
 Typically have
and
distribution and a
degree of binding to
udder tissue.
 Results in lower
concentrations of drug
residues in the milk
 In what instance do you
think would we use this
route of administration?
 Other parenteral administration routes are listed in Table 3-1
in your textbook. READ IT…IT IS TESTABLE MATERIAL!!!
Local Routes of Administration
 Inhalation administration
introduces drug to the
animal by having it
breathe the drug into the
lungs
 RAPID ABSORPTION;
particles diffuse across the
alveolar membrane and
enter blood capillaries.
 Must be AEROSOLIZED,
VOLATILIZED, or NEBULIZED
 Topical medication goes
on the surface of skin or
mucous membrane
systemic
absorption rate
 Used for
 GELS
treatment
 Fur and feathers inhibit
good skin contact.
 Includes OPHTHALMIC
and OTIC medications.
 LINIMENTS
 TINCTURES
 OINTMENTS LOTIONS
 CREAMS
 POWDERS
 PASTES
 AEROSOLS
Rectal
 ALTERNATIVE for delivering drugs
to animals that present dangers to
the vet staff or animals in very poor
condition where other methods of
admin. are not practical.
 Anticonvulsants, analgesics,
antiemetics
 Local irritation is a potential side
effect of rectal drug therapy.
 Suppositories are designed for
PR admin., however, other drug
forms can be successfully admin.
PR.
Transdermal
 Delivered SYSTEMICALLY through a patch on the skin
 Through the patch, drug passes from skin to bloodstream
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allowing it to be delivered slowly and continuously (hours,
days, or longer)
Plasma levels = relatively CONSTANT
Skin irritation is one side effect
Useful for drugs that are normally eliminated rapidly from the
body
Only drugs needed in relatively small daily doses can be given
through patches
Typically mixed with chemical to enhance skin penetration
Ex: Fentanyl and Niroglycerin
Enteral Administration:
Oral Route (PO)
 Delivers drug directly to the GI tract
 Most
route of admin.; LEAST LIKELY to
cause adverse reactions
onset of action;
duration of activity
 Absorption is not always predictable.
 Affected by GI disease, A&P of digestive tract
 Before entering the bloodstream, an oral drug must be:
released from the dose form
2. transported across the GI tract
3. passed through the liver
1.
Solid Dose Forms
 TABLETS
 Enteric-coated
 Sustained-release (SR)
 Scored
 MOLDED TABLETS
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CAPLETS
CAPSULES
LOZENGES
BOLUSES
 Via “balling gun”
 POWDERS
Liquid Dose Forms
 Given via dropper, syringe, or
drench or mixed with food.
 SOLUTIONS
 Syrups (85% sucrose)
 Elixirs (sweetened alcohol)
 Tinctures (alcohol)
 SUSPENSIONS
 EMULSIONS
 Can you think of any
contraindications here?
 Advantages/disadvantages of
giving with food?
Absorption of Oral Drug Forms
 Transport across the GI tract determines how long it takes
for a drug to enter the bloodstream.
length of time in ruminants and herbivores
(horses, rabbits, etc.)
 The more
the digestive tract, the
it
takes to attain therapeutic blood levels.
 Drug passage through liver affects drug concentration in
the blood.
 “First-Pass Effect”
 Liver alters drug and makes it less (or more) active
Drug Dose
 The dose of a drug is the amount of drug administered at one
time to achieve the desired effect (can be in mL, cc, mg, g,
tablets, etc.)
 Loading dose: initial dose of drug given to get the drug
concentration up to the therapeutic range in a very short
period of time
 Maintenance dose: dose of drug that maintains or keeps the
drug in the therapeutic range
 Total daily dose: total amount of drug delivered in 24 hours
Drug Dosage
 The dosage of a drug is the amount of drug per
animal species’ body weight or measure
 Examples include mg/kg or g/lb
 Dosage interval: how frequently the dosage is given
 Examples include BID or TID
 Dosage regimen: dosage interval and the dosage
together
 Examples include 30 mg/kg TID and 5 g/lb BID
Drug Toxicity
 Drug toxicity may be due to human error or be
related to side effects of the drug
 Examples of drug toxicities:
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Outright overdose
Relative overdose
Side effects
Accidental exposure
Interaction with other drugs
Incorrect treatment
Counteracting Drug Toxicity
 Veterinary staff must act quickly to counteract any
problems caused by drug treatment.
 Some ways to treat drug toxicities:
 Removal of the offending drug
 Enhancing drug removal by the animal (inducing emesis,
administering fluids, etc.)
 Counteracting with an antidote
 Providing symptomatic care or nursing care until the
toxicity signs have diminished