Principles and Methods of Drug Administration

CHAPTER 3 -3CHAPTER 3 -3

Dr. Dipa Brahmbhatt VMD MpHDr. Dipa Brahmbhatt VMD MpH

dbrahmbhatt@vettechinstitute.edudbrahmbhatt@vettechinstitute.edu

Parenteral vs. Non-Parenteral Administration Routes

Parenteral Administration

• Literally means “administered in the space between the enteric canal (the GI tract) and the surface of the body”

Non-Parenteral Routes

• Drugs given by mouth = Oral administration (PO)

• Rectally

• Sublingual

Other Parenteral Administration Routes

• Inhalation administration introduces drug to the animal by having it breathe the drug into the lungs– Particles diffuse across the alveolar membrane

• Topical medication goes on the surface of skin or mucous membrane– Forms of topical medication are summarized in Table 3-2

in your textbook

• Other parenteral administration routes are listed in Table 3-1 in your textbook

Route of Administration

• Injectable / Parenteral

• Local Routes– ‘Applied or given directly where the action of the

drug is desired’– Inhalation, topical (skin, eye, ear), other routes

(rectal, vaginal, transdermal patches)

• Oral Route

Inhalation

• Drugs are administered in the form of a gas/spray and are rapidly absorbed into the bloodstream.

• An animal breathes in the drug > the lungs > alveoli where the particles diffuse into the bloodstream > distributed throughout the body

Drugs inhaled are rapidly absorbed in

the bloodstream

Inhalation

• Gas Anesthesia (most common)– Drugs are volatilized (turned into gases)

from liquids using a vaporizer

• Treat respiratory conditions – Bronchodilators (anticholinergics),

mucolytic enzymes, antibiotics, steroids– Drugs are nebulized (turned into a fine spray)

Topical

• Dermatology (ear: drops, ointments and cream) and and ophthalmology (liquid drops and ophthalmic ointment)

• Applied to the skin surface or mucous membranes• Forms: gel, ointment, cream, paste, liniment, lotion,

powder, aerosol, or liquid drops• First dissolved and then diffused into the skin• Slowest route of absorption in the body as a whole• High concentration of drug locally,

may be absorbed systemically

Topical

• Localized skin infections/ allergies, abrasions

• May be irritating, animal may chew/lick it off

• Easy to administer

• Can use drugs that otherwise

would be toxic if injected

• Have to shave fur for good

contact

• Other topical routes: nasal, rectal, vaginal

Topical• Solution: Clear liquid preparation, 1/more solutes and

1/more solvents

– Solvent: the dissolving substance of a solution

– Solute: the dissolved substance of a solution

• Emulsion: A mixture of 2 immiscible liquids, one dispersed throughout the other in small droplets

– Water – oil emulsion

• Suspension: A finely divided, undissolved substance dispersed in water/oil. Liquid preparation that contains solid drug particles suspended in a suitable medium

FORMS OF TOPICALSDrug suspended in….

• Aerosols – solvent packaged under pressure

• CREAM – water-oil emulsion

• GEL – semisolid or jelly-like substance

• Liniments – oily, soapy, or alcohol-based substance. Applied with friction

• Lotions – liquid for dabbing, brushing, or dripping on skin without friction

• OINTMENT – semisolid, lipid - based preparation that melts at body temp

• PASTE – semisolid that retains its state at body temp

• Powder – powder for external lubrication or absorption

Rectal Drug Administration• Alternative for delivering drugs: dangers presented

to the vet staff / inability to administer the drug because of the animal’s condition

• Usually much slower than oral

drug absorption

• Local irritation is a side effect

of rectal drug therapy

• Suppositories: melt/dissolve when inserted in body orifice

Vaginal Drug Administration

• Therapeutic macromolecules• The rate and extent of absorption depends on

– Drug formulation factors

– Vaginal physiology

– Age of the patient

– Phase of the estrous cycle of the patient

• Vaginal drug delivery systems include– Controlled internal drug release devices

– Progesterone-releasing intravaginal devices

– Vaginal sponges

Transdermal Drug Administration

• Delivered through a patch on the skin

• It passes from skin to

bloodstream :drug to be

delivered slowly and

continuously (hrs/ days/ longer)

• Skin irritation is one side effect

• Only drugs needed in relatively small daily doses can be given through patches

Inhalation Topical Rectal Vaginal Transdermal

Field •Anesthesia •Dermatology/ Opthamology

•General •Reproductive •Orthopaedics

Example •Gas masking•Endotracheal gas anesthesia•Nebulization

•Skin•Conunctiva•Subconjunctival•Eye/ Ear

•Anticonvulsants•Analgesics•Antiemetics

•CIDR, PRID •Nitroglycerin •Fentanyl

Functions •Rapid blood levels •+/- systemically •Absorbed lower than oral (small SA or formulation: solid, liq., semi-solid)

• Variable •Constant plasma levels: delivered slowly and continuously over an extended period of time

Pros •Anesthesia•Emergency procedures•Respiratory disease

•Good local effect•Easy to administer•If toxic IV

•Fractious animals•Poor condition of patient

•Quickly eliminated from body

Cons •First dissolve than penetrate•May be irritating•Chew/ lick/ rub•Clip for good skin contact

•Local irritation

•Depends on formulation, physiology, age, phase of estrous cycle•Retention of unit

•Mixed with chemicals to enhance skin penetration (blood)•Skin irritation

Nonparenteral Administration Routes

• Delivered directly to the GI tract

• Most convenient (owner can do)

• Before entering the bloodstream: oral drug must

be released from the dose form, transported across the GI tract, and passed through the liver (reduces amount)

• Long duration of activity, slow onset of action

• Relatively safe (less likely for adverse effects)

• No need for sterility

• Gastric acid and disease may affect absorption rate

• Ruminants have questionable absorption

• Must get through GI mucosa

Oral Meds

• Orally administered drug gets into bloodstream– Dissolving the drug form (solid / liquid)

• Solid: tablet (sustained released, molded), capsule, powder, bolus, lozenges

• Liquid: Solution, suspension, emulsion

– Transport across GI tract– Drug passage through the liver

Oral Meds• Released from its form (tablet, capsule, liquid,

powder, bolus, lozenges) after the animal swallows it

• Tablets – Disintegrate in stomach liquid– Some tablets have an enteric

coating (don’t break), meaning the drug does not dissolve (neutral/ alkaline pH) until it reaches the SI

– They cause less stomach irritation

Oral Meds

• Sustained released tablets– Coated so released in controlled fashion– Crystal of KCL on wax,

microencapsulated drug (small drug particles with polymer coating)

• Molded tablets– Soft, chewable – Mixed with lactose, sucrose, or dextrose and frequently a

flavoring (Heartguard)

Oral Meds

• Capsules – Gelatin shell (dissolves in stomach liquids)– Holds in the powdered or liquid medication

• Boluses are large rectangular tablets used in large animals

• Lozenges are in a hard, slow-release form. Not practical in animals (they will chew it)

• Powders are dry and granulated and mixed with inert bulking and flavoring agents for dilution. These are easily mixed with food

Liquid Oral Drug

• SOLUTIONS- drug is dissolved in liquid. Will not settle out if left standing (syrups, elixirs)

• SUSPENSIONS- finely divided undissolved substance dispersed in water (shake the container to distribute)

• EMULSION – fine droplets of oil in water or vice versa. Separate if standing for long periods of time. Must shake vigorously

• All 3 can be mixed with food. Liquids don’t irritate the stomach as much as solid meds because they don’t settle out in a focal spot.

Liquid Oral Drug

• Solutions, Suspensions and Emulsions– Mixed with food– Don’t irritate the stomach as much as solid meds

because they don’t settle out in a focal spot– Not as accurate dose in food– Option for aggressive patient

Transport Across GI

• Species anatomy can affect drug absorption – Ruminants

• Longer to respond ( 3days)• Can be ineffective• Longer to reach therapeutic

levels in blood

– Horses: modified mono

gastic, continuous grazers so

some drugs absorbed rapidly

others slowly

– Monogastric

Liver

After the drug is absorbed by the GI tract, it must pass through the liver. The liver affects blood levels because it can alter a drug. BE CAREFUL with drug choices when the liver is not functioning properly.

General Guidelines

• Table 3-5: Pharmacological Aspects of Nursing Care

Therapeutic Range

• Drug Factors

–Route of administration

–Drug dosage

–Dosage interval

Dose

DOSE = the amount of drug administered at one time to achieve the desired effect

mL, cc, mg, Tablets

Drug Dose

– LOADING DOSE – • the initial dose of a drug given to achieve drug levels in

the therapeutic range in a short period of time

• Large amount of drug initially / normal amount more often

– MAINTENANCE DOSE – dose maintains drug in the therapeutic range

– TOTAL DAILY DOSE – amount of drug given in 24 hours (ex: 1200 mg per day)

Drug Dosage

– DOSAGE – amount of drug per animal’s body weight (ex: 5 mg/kg, 1g/lb, 60 mEq/kg )

– DOSAGE INTERVAL – how frequently the dosage is given (SID, BID, TID, Q24H, Q12H, Q8H, Q6H, QD, Q2D, PRN, etc)

– DOSAGE REGIMEN (30mg/kg tid, po X 7 days)

• Dosage

• Dosage interval

• Administration route

• Duration of treatment

Drug Toxicity

• Drug toxicity may be due to human error and/or accident

• Drug toxicity may be related to side effects of the drug

• Examples of drug toxicities:– Outright overdose– Relative overdose– Side effects– Accidental exposure– Interaction with other drugs– Incorrect treatment

Your patient is reacting to the medication, now what?

• Directly remove the drug– Wash off the topicals, induce emesis for those

ingested

• Activated charcoal to bind what cannot be vomited

• IV fluids to support the kidneys• Give an antidote if there is one• Provide care until the animal is through the

toxicity

KEEP YOUR PATIENTS SAFE!