Routes of administration of drugs and Posology (Exam 1) Flashcards
2 factors affecting selection of the route of administration
- therapeutic factors
2. drug factors
therapeutic factors
- onset and duration of action
- site of action
- adverse reactions
drug factors
- irritation
- solubility
- pH
routes of administration
- local
2. systemic
local routes of administration
site of administration is where action is
skin, nasal, conjunctival, urethral and bladder, vaginal, rectal, mammary, sublingual, GI tract, otic, epidural, intraspinal, intrasynovial (intra-articular), intramedullary (into bone marrow)
systemic routes of administration
distributed all over the body to reach site of action
- oral (per os, enteral)
- paternal or by injection (IV, SQ, IM, IP)
- inhalation (gases, vapors, aerosols)
What does IP stand for?
Intraperitoneal
advantages of oral administration
- safe
- convenient in some animals
- economical
- no problem of infection
disadvantages of oral administration
- inactivation of some drugs by gastric acidity, digestive enzymes or rumen microflora
- the presence of food may affect absorption
- the presence of drugs may affect absorption
- activity of the GI tract affects absorption
- irritant drugs may cause vomiting and diarrhea
- onset of action is slow
- unpalpability of some drugs
advantages of intravenous
- accurate
- fast onset of action
- irritating, hypertonic, acidic or basic drugs can be given
- large volumes can be given
disadvantages of intravenous
dangerous (leak, overdose, can’t find vein, costly)
advantages of intramuscular (IM)
- rapid absorption
- Duration of action is longer than intravenous
- suspensions can be injected
disadvantages of IM
irritant, hypertonic, acidic or basic drugs may cause tissue damage
advantages of subcutaneous (SQ)
- slow absorption but constant
2. longer duration of action
disadvantages of SQ
- slow onset
2. irritating drugs can not be used
What is posology?
the study of doses
What is the difference between dose and dosage?
dose is the amount of drug given to an animal and dosage is the amount of drug per unit body weight
What are the 3 types of doses?
therapeutic (effective) dose
toxic dose
lethal dose
minimal therapeutic dose
smallest amount that has a therapeutic effect
maximal therapeutic dose
largest amount that can be tolerated without producing toxic effect
therapeutic dose
optimal dosage which lies some place between the minimal and maximal therapeutic doses
What is ED50?
the effective dose in 50% of animals
aka median effective dose
True/False LD0 is nontoxic
False. it doesn’t kill, but it is toxic
lethal dose
dose that causes death
toxic dose
amount that produces undesirable effects
What are the two ways relative safety is evaluated?
the therapeutic index and the standard safety margin
what is the therapeutic index?
the ratio between the LD50/ED50. the larger the therapeutic index, the wider the margin of safety of a drug
what is the standard safety margin and how do you measure it?
expresses the percentage dose increase between ED99 and LD1
(LD1/ED99 - 1) x 100
the wider the margin between ED99 and LD0 for a drug the _____ the drug
safer
which is more accurate- the therapeutic index or the SSM?
standard safety margin
what is the therapeutic window?
difference b/w minimal and maximal effective dose
