Drug Administration Routes Slides- 2 Flashcards
Why does the route matter?
The route by which a drug is administered can affect markedly one or more aspects of a drug’s action. Administration routes are often limited by the properties of a drug.
Ex: Lidocaine 2% HCl
Local anesthetic- subQ or transdermal administration, accompanied by epinephrine to combat vaso dilation.
Anti-arrhythmic agent- IV given without epinephrine.
Colic treatment and pre-anesthetic agent- IV.
Enteral
From Greek work enteron (gut). Refers to any route which place the drug directly into the GI tract. Most commonly means oral medication. Other routes: rectal, sublingual.
Parenteral
From Greek work para (beside). Refers to any route which places the drug outside the GI tract.
IM, IV, SC, transdermal.
More invasive than oral route and requires aseptic technique. Improved tissue targeting, and control of systemic drug levels.
Risk from injection: irritation, inflammation, allergic reactions and nerve damage.
Oral drug administration
Abbrevaited as PO meaning per os “by mouth”. Most drug absorption occurs in the lower GI tract rather than the stomach or rumen.
Dangers of enteric coated pills
If you break them in half it can effect how quickly the drug is processed.
Factors that effect the absorption of oral drugs
Physicochemical interactions- food, GI tract acidity.
GI motility- Drugs, diseases.
GI microflora- Great species variation.
Mucosal Dysfunction- Disease, Drugs.
What drugs are suitable for oral administration?
Low molecular weight, lipid soluble, acid-resistant, partially resistant to liver metabolism.
Advantages of oral administration
“Relatively” easy.
Non-invasive.
May be reversible.
Limitations of Oral drug administration
Delayed onset, variability, influenced by GI motility.
GI irritation as side effect.
Vomiting, diarrhea, fractious animals.
The relationship between oral dose and absorption is NOT directly proportional for most drugs.
Noteworthy species differences for oral drugs
Monogastrics- high acidity, small volume.
Ruminants- lower acidity, large volume, diverse microflora.
Safety considerations of parenteral drug administration
Have to maintain sterility. Follow manufacturer’s guidelines for storage. Protecting yourself and others by wearing personal protection equipment, washing hands, don’t recap needles, disposing sharps.
Things to consider: single verse multi use vials, proper storage, reconstitution instructions, expiration date.
Choosing the right needle & syringe
Influenced by several factors: solution or suspension, chemical nature of drug, viscosity, size of patient and skin thickness.
Subcutaneous
A drug injection into the loose connective tissue under the dermis. Suitable for solutions, suspensions or solid formulations. Provides good albeit relatively slow absorption, because tissue is not richly supplied with vessels. Duration of drug action can be formulation dependent. Loose skin over the shoulders/neck is an ideal injection site.
Better absorption for subcutaneous
Small, lipophilic, uncharged. Increased local blood flow makes for better absorption.
Major limitations of subcutaneous injections
Unsuitable for irritants. No drugs in oily vehicles. Slow and variable absorption.
Transdermal drug delivery
Formulation in which a drug is combined with a vehicle (penetration enhancer) that promotes drug passage through intact skin.
Potential advantages: constant rate of drug delivery, simple and convenient, ease for owners, less side effects than oral meds.
Has many unknowns- unproven efficacy, risk of other animals/children being exposed.
Intramuscular
A drug injection into a large mass of skeletal muscle. Rich blood supply so absorption is faster. Fewer pain receptors than skin. Better than SC for mild irritants. Can be used for oily solutions.
Intramuscular injection sites
Goal is to target a large muscle mass but avoid nerves, ligaments, and bones.
Dogs: thigh m or hamstring m avoid sciatic.
Cats: quadriceps m or dorsal lumbar m.
Horse: base of neck or semitendinosus m.
Intravenous
Injection of a drug solution into a major vein. Rapid effect. Preferred route for irritants and large volume infusions. Involves no absorption- drug has 100% bioavailability. Allows precise control of plasma drug level- dose to effect. Considered irreversible. No oily vechicles. Sterile particulate free solutions only. Shorter more intense actions.
