Unit 1- Routes of Administration Flashcards
Enteral
Oral, intrarumenal, rectal
Parenteral
Intravenous, intramuscular, subutaneous
Common Parenteral
Epidural, intradermal, intratracheal, intraperitoneal,
Rare Parenteral
Intraarterial, intramedullary, intracardiac, intrathecal, intrathoracic, subarachnoid
Other routes of administration
Inhalation, topical, oral transmucosal
Choice of route of administration
Physiochemical properties, formulation, therapeutic indications, pathophysiology of disease, targe species
Purpose of drug therapy
To induce a desired pharmacologic response
Plasma Drug Concentrations
Used to approximate drug concentrations at the tissue site
Determinants of PDC
Drug must be absorbed, free drug is distributed to tissues, hepatic metabolism or biliary excretion eliminates drug from the body
Most important site of metabolism
Liver
Absorption
Movement of the drug from site of administration into the blood, drugs must cross one or more lipid membranes
Gastrointestinal Absorption
Heterogeneity causes regional variation in absorption, most drugs absorbed through small intestine
Obstacle to GI Absorbtion
Interspecies diversity in comparative GI anatomy and physiology
Factors affecting GI absorption
GI Ph, surface area, motility, concentration of drug, permeability of mucosa, intestinal blood flow
First Pass Metabolism
After GI absorption, drugs enter portal vein and then the liber, and are metabolized
Sublingual Drug Absorption
Systemic drugs
Buccal mucosal Absorption
Polymer patches and feline oral sprays
Esophagus Absorption
Cornified epithelium decreases absorption
Stomach Absorption
Simple mucosa allows absorption, mucus may be a barrier, acidity and motility provides harsh environment
Small Intestine Absorption
Primary site for drug absorption, blood flow greater than stomach, microvilli increase surface area
Presystemic Metabolism
Epithelial and bacterial biotransformation in small intestine
Second First-Pass Effect
Epithelial cells of the intestine are endowed with necessary enzymes for drug metabolism
Third First-Pass Effect
Resident microbes are capable of metabolizing specific drugs
Disintegration
Solid dosages physically disperse so particles can be exposed to GI fluid
Dissolution
Pharmaceutical phase, drug molecules enter into solution
GI Absorption
Drugs must be dissolved in aqueous intestinal fluid to be absorbed across the intestinal mucosa
Parenteral Manufacturing
Strict guidelines to eliminate contamination, sterile preparation
Primary Parenteral Routes
Subcutaneous and intramuscular
Parenteral Injection
Injected into well perfused tissue, systemic capillaries drain into venous circulation, bypassing all defensive mechanisms
Irritating Injections
Can be done IM but may cause reaction and necrosis
IM action duration
Longer than IV but shorter than SC
Intraperitoneal Administration
Large volumes can be administered, good mixing with peritoneal fluid, majority of drug enters portal vein and undergoes first-pass metabolism
Intravenous Administration
No absorption process, rapid onset of action, large volume possible, irritating solutions can be injected slowly
Inhalation
Gases are absorbed into pulmonary circulation
Inhalation of 2 μm particles
Nebulized particles inspired into alveoli
Inhalation of 5 μm particles
Reach the respiratory bronchioles
Inhalation of 5-10 μm particles
May reach the upper respiratory tract and large airways
Inhalation Response
Rapidly absorbed and highly perfused, enter pulmonary veins draining to systemic circulation
Topical Administration
Can be applied to skin or mucous membranes for desired local response
Topical Routes
Sublingual, intravaginal, intranasal, intrauterine, rectal, preputial, ocular, aural
Oral Transmucosal Administration
Drugs given into buccal cavity to be absorbed through mucosa to avoid GI and first-pass metabolism
Bioavailability
Percentage of an administered dose that reaches systemic circulation
Determining Bioavailability
Comparing plasma levels after administration with plasma levels from IV administration, will be less than 1 (100%)
Predicting Drug Efficacy
Using bioavailability of different routes of administration
