Pharmacokinetics - LADMER Flashcards
definition of pharmacokinetics
describes the relationship between dose and unbound drug concentration at the site of action and the time course of drug concentration in the body
L.A.D.M.E.R
Liberation
Absorption
Distribution
Metabolism
Elimination
Response
types of liberation (Administration options)
Topical
injection
oral
inhalation
rectal
vaginal
how to choose your administration route
drug design - chemical and physical properties
need for local or systemic effects
patient compliance
bioavailability
duration of action
cost
side-effects
Topical
includes creams , ointments , eye ear and nasal drops , patches
advantages of topical
local site of action
limited side effects usually to site of application
known duration of action
better physical tolerance compared with injections/oral - may improve compliance
patches may have prolonged effects - buprenorphine have a 7 day period
disadvantages of topical
limited choice of drugs - related to molecular size and lipid solubility
duration of action can be limited
can prove troublesome to use e.g if large areas are to be covered , drops require manual dexterity to use correctly - this may reduce compliance
shelf life may be limited so it can be relatively expensive
Injections
intravenously - Parenteral - IV
intramuscularly - IM
intrathecally - spinal
intra-particularly - joint
sub-cutaneously - below the skin
intra-dermally - skin
injections - advantages
rapid acting effects usually appear within minutes if not seconds
bioavailability - 100 percent usually
useful if systemic effects required urgently - except intra-articular
duration of action usually well known - but may be very short
useful alternative for patients who are very ill or unconscious
disadvantages of injections
expensive compared to oral and topical
invasive - risk of infection
unpleasant for patients so may reduce compliance
normally short duration of action so may require multiple dosages through the day - expensive
side effects may be more pronounced
oral
tablets , capsules and liquids
advantages of oral
convenient
usually cheap compared to injections and topical forms
easy to take
better compliance
disadvantages of oral
bioavailability - variable dependent on range of factors
duration of action may be unknown or variable between patients
slow onset of action
rectal and vaginal
suppositories , pessaries , creams , ointments and sprays
advantages of rectal and vaginal
useful for local effects
relatively cheap
can by-pass first pass metabolism