Chapter 1

Technician’s role with medication

• giving the right med at the right time through right route

• educating clients

• accurately recording information and labeling

• monitoring patient’s response to drug

• question unclear orders

Where do drugs come from

• plants,

• minerals

• animals

• bacteria and mold

• labs

Inactive ingredients

• binders

• fillers

• flavor and coloring agents

• sweetening agents

• thickening agents

how we choose drugs for patients: Diagnostic

using PE, labs, other dx tests to determine cause of illness

how we choose drugs for patients: Empirical

• based on experience

how we choose drugs for patients: Symptomatic

• cause unknown , treating signs only

Regimen

• A plan for drug administration

• Regimen must consider:

  • Route, dose, frequency, duration

Prescription/ legend drugs

• FDA determined drug to have potential toxic effects and must be administered in a way that requires a trained personnel

• Must have statement saying the use of the drug is restricted to use by or on order of a licensed veterinarian

OTC drugs

• FDA determined drug does not have enough potential to be toxic or need to be used under veterinarian supervision

controlled drugs

• drugs that have abuse potential

Pharmacokinetics

• complex sequence of events after drug is administered into a patient

Biotransformation

• Also called metabolism.

• Body’s ability to change a drug from the form it was ingested in, into a form in which it can be excreted from the body

How drugs travel in the body

• Drug is administered > absorbed (in the intestines (if orally or rectally given), liver, and blood plasma) (equilibrium is reached between the drug amount in the blood plasma and amount at the cellular receptor sites) > drug distributes through the body’s tissues and to the site of action (where it can attach to cellular receptors in order to give desired effect) > biotransformation occurs (primarily liver but also other parts of body) which converts the drug into a form that can be excreted from the body

Oral administration

• Absorbed more slowly than injections but also lasts longer

• given by PO, nasogastric, or orogastric

• affected by pH, size of molecule, solubility, food in the GI tract, species differences, motility

• Should not be used in patients with diarrhea or emesis

Parenteral administration: IV

• Most rapid onset but shortest duration

• used if the drug is irritating to tissues

• Should reinsert if the vein is blown

• give slowly to lessen chance of reaction

Parenteral administration: IM

• slower onset than IV but longest duration

• affected by form (water fastest vs lipid soluble or microfine crystals)

• always pull back on syringe

Parenteral administration: SQ

• slower onset than IM but slightly longer duration than IM

• amount that can be given depends on loose skin available

• giving 5% dextrose this way can cause skin to slough

Parenteral administration: ID

• Usually for allergy and TB testing

• shallowest angle of needle insertion

Parenteral administration: IP (Intraperitoneal)

• Directly into the abdominal cavity

• onset and duration variable

• used when other routes unavailable

• may cause adhesions or organ puncture

Parenteral administration: IA (Intraarterial)

• Accidental in most veterinary settings (artery right next to vein)

• caution in large animal- high concentration of drug to brain can cause seizures or death

Parenteral administration: intraarticular

• directly into a joint, usually for inflammation

• must be sterile technique

• usually done by DVM

Parenteral administration: IC (intracardiac)

• through the chest wall into heart chambers

• drug delivered quickly to all tissues

• CPR or euthanasia

Parenteral administration: Intramedullary

• directly into bone marrow (typically femur, humerus, tibia)

• used in animals with very small veins or low blood pressure

• to deliver blood or fluids

• not commonly used

Parenteral administration: epidural/subdural

• epidural- outside the dura mater (meninges- layers of the spine)

• subdural- inside meninges (location of CSF), also called intrathecal

• used for spinal anesthesia or contrast agents

• usually done by DVM

drug administration by Inhalation

• liquid converted to gas form

• vaporizer or nebulizer

topical drug administration

• place on skin or mucous membranes

• transdermal drugs

bioavailability

• degree to which a drug is absorbed and reaches general circulation

Factors affecting bioavailability

• mechanism of absorption

• pH and ionization status of the drug

• absorptive surface area

• solubility of the drug

• status of GI tract

• interactions with other medications

• dosage form

Passive transport

• no energy expended

• goes from area of high concentration to low concentration

• may or may not use carrier

Active transport

• cell expends energy

• go from low to high concentrations n

Drug transporter

• P-glycoprotein (is made by MDR1 gene)

• uses energy to pump drug away from protected sites ( some breeds lack this which can cause toxicity when taking certain medications)

Factors affecting absorption

• ionization

• surface area

• blood supply

• solubility

• formulation of drugs

• drugs given orally

• 
  

Fat soluble, non ionized drugs absorb the best because cells have a lipid layer and fat more easily dissolves in fat

How ionization affect absorption

• nonionized (drugs without a charge) absorb better and can undergo passive transport

how surface area affect absorption

• greater surface area = greater absorption

How blood supply affect absorption

• greater blood supply, greater absorption

First pass effect

• drugs in GI tract absorb into portal vein and passes into liver first before general circulation

• Liver metabolizes drug into other forms (0ften inactive or less active), these enter general circulation

Drug distribution