unit 2 Flashcards
bioavailability
the amount of drug in the blood that is free to bind at specific target sites to elicit drug action
bioavailability depends on:
route of administration, absorption and distribution, binding, inactivation (metabolism), excretion
oral delivery
advantages - relatively safe, convenient, economical
disadvantages - irritation, nausea, possible destruction by acid or enzymes, complexes with substances in GI tract, relatively slow onset for emergency use, cannot be used in unconscious or uncooperative patient, possible “first-pass” effect, absorption is often irregular and incomplete
sublingual delivery
advantages - eliminates “first pass” effect, polypeptides are absorbed
disadvantages - drug can be irritating or have bad taste
rectal delivery
advantages - can be used in an unconscious patient, can be used in vomiting patient, relatively rapid absorption, eliminates first pass effect, convenient for administering drugs to neonates and young children
disadvantages - lack of compliance
intravenous delivery
advantages - complete dose enters the blood, rapid onset of action, controllable rate of absorption, sterile conditions are needed
disadvantages - not easy for self medication, drug must be water soluble, can be painful
subcutaneous delivery
advantages - by altering the vehicle, the duration of action of many drugs can be prolonged, pellets can be used
disadvantages - irritating drugs cannot be used, absorption cannot usually be controlled
intramuscular delivery
advantages - rapid absorption of drugs in aqueous solutions, can use depot forms and thereby prolong the duration of action of many drugs
disadvantages - irritation is a slight problem, possible injection into blood vessel
intraperitoneal delivery
advantages - rapid absorption
disadvantages - infection and adhesions
intra-arterial delivery
advantages - high concentration in a particular organ or area
disadvantages - difficult access, danger of hemorrhage
intraspinal delivery
advantages - ensure entry into CNS
disadvantages - difficult technique
inhalation delivery
advantages - very rapid absorption
disadvantages - best for gaseous and volatile liquids, must use aerosol of very fine particle size if drug is not volatile; hard to control the amount of dose absorbed, irritation
topical delivery
advantages - usually produces a local effect without systemic effects, but can also be used for producing systemic effects
disadvantages - possibility of the absorption of a large amount of drug into blood, drug must not be irritating
intracranial delivery
advantages - primarily for experimental use, parenchymal, intraventricular
absorption of drugs
molecules cross membranes by:
- simple diffusion
- facilitated diffusion
- active transport
-gated channels
- pinocytosis/exocytosis
factors that determine the passage of molecules across membranes
solubility, size, polarization, ionization
drugs tightly bound to plasma proteins
have a limited distribution to tissues
tissues involved in metabolisms and excretion
tend to concentrate drugs and or drug metabolites
amine drugs
amphetamine, imipramine are usually found in high concentrations in tissues
acidic drugs
often highly bound to plasma proteins and are not found in very high concentration in tissues
the highest concentrations of a drug are not necessarily
found in those tissues in which it exerts its action(s)
the degree of distribution depends on
the delivery of the drug by the circulatory system, the ease of the drug crosses membrane barriers and the extent the drug is bound to plasma proteins
many drugs bind _____ to albumin and certain globulins in the plasma
reversibliy