Pharm2 Flashcards
Therapeutic range
concentration of the drug you need to get in circulation to see the therapeutic effect being manifest
Dosage Regimen
• The amount, route, frequency, and duration of drug administration
• Determines the amount of drug being administered to an animal, based on:
1. Dose
2. Dosage interval
Route of Administration
• Drugs must be administered in a form and by a route that will allow them to reach their target site in the body
o Topical
o Oral
o Inhalation
Dose
Amount of drug given at one time (dry weight measure)
Dosage interval
length of time between administration of separate doses (e.g. 6,8, 12, 24 hrs.)
Topical
Local effect
Oral
by mouth
Slow systemic effect, less absorption vs. IV routes
Parenteral
drugs administered by injection
Route of systemic effect vs local effect
IV, IM, SC (systemic effect)
Intraarticular, Intraocular, Intradermal, Intraperitoneal, Intramedullary (local effect)
Pharmacokinetics- steps
- Drug Absorption
- Drug Distribution
- Drug Metabolism
- Drug Elimination
Pharmacokinetics
Sequence of events that occur once a drug is administered
Drug Absorption
• Movement of drug from administration site into systemic circulation
What can affect drug absorbtion
route of administration drug’s hydrophilic/lipophilic nature drug form GI tract condition Liver metabolism after GI absorption Blood perfusion at administration site
Bioavailability
the proportion of drugs administered that makes into the systemic circulation.
Hydrophilic molecules
(ionized)
diffuse through fluid between cells
Lipophilic molecules
(non-ionized)
diffuse across cellular membranes
Drug Distributions
- Once in the systemic circulation drug must be distributed to target tissues
- By passive diffusion
- Initial distribution is to highly perfused tissueàbrain/vital organs
- Drugs enter target tissue at capillary level – capillary wall is thin
The concentration reached by a drug in the blood stream is affected by:
o the fluid volume into which it will be distributed
o The extent to which it will be distributed throughout the body
Drug Metabolism
Biotransformation
• Enzymes in the body transform drugs into secondary compounds (i.e. metabolites)
Step 1 Original drug->Metabolite 1
Step 2 Metabolite 1->Metabolite 2 (
Combine Metabolite 1 with glucuronic acid, sulfate, glycine
• Metabolites are hydrophilic and easily excreted in urine
• Metabolism occurs chiefly in the liver
• Drug interactions can occur during metabolism
• Drug metabolism differs between species and even between individuals of the same species
Drug interactions can occur during metabolism
- Competitive inhibition
* Enzyme induction
Drug Elimination
• Removal of a drug from the body occurs at the kidney and at the liver
• Renal excretion is the most important route
*Poor renal blood flow can lead to toxicity
• Drug elimination rates are dependent on a drug’s half-life
• Drug’s half-life is used to determine dosage interval and withdrawal time
