601501
Drug Administration
- Oral
- Advantages
- easy and convenient
- no skilled personal required
- prep need not be sterile
- immune system can cope
- easy and convenient
- stomach
- pH = acidic
- Acid drugs
- mainly non-ionised
- readily absorbed
- mainly non-ionised
- Basic drugs
- mainly ionised
- poorly absorbed
- mainly ionised
- Neutral drugs
- readily absorbed
- readily absorbed
- pH = acidic
- Duodenum
- pH = alkaline
- basic drugs => mainly non
ionised, readily absorbed
- Acidic drugs => mainly
ionised, absorption
restricted
- pH = alkaline
- Disadvantages
- effects are slow
- absorption maybe incomplete
- some drugs to big to be absorbed
- some drugs destroyed by gut or liver
- effects are slow
- Advantages
- INHALATION
- Large surface area of alveoli in lungs
- good pulmonary blood supply
- can have local effect on lung
- systemic effects e.g. general anaesthetic
- Large surface area of alveoli in lungs
- INJECTION
- by-pass difficulties of absorption
- drugs must be sterile => by
passing immune system
- exact dose is known
- given by skilled staff
- by-pass difficulties of absorption
- INTRAVENOUS
- Advantages
- rapid effect
- lage volumes can be used
- Irritant solutions can be used
- rapid effect
- Disadvantages
- rapid delivery to heart, CNS => side effects
- cannot recall drug
- rapid delivery to heart, CNS => side effects
- Advantages
- INTRAMUSCULAR & SUB-CUTANEOUS
- Advantages
- controlled onset with drug vehicle
- aqueous - rapid effect
- oily -slow effect
- controlled onset with drug vehicle
- Disadvantages
- Damage at injection site
- Limited to small volumes
- Damage at injection site
- Advantages
- ROUTES determined by
- drug chemical nature
- how quickly an effect is required
- how the effect needs to be maintained
- patient condition/compliance
- Convenience
- many drugs bind to a plasma protein
- bound fraction retained in
plasma
- unbound fraction diffuses into tissues (active)
- bound fraction retained in
plasma
- drug chemical nature
- DISTRIBUTION
- out of plasma into tissues
- move easily into
interstitial fluid around
tissues, interact with
target
- Distribution AWAY from target site => terminate effect
- out of plasma into tissues
- BLOOD-BRAIN/BLOOD-PLACENTA
BARRIER
- Capillaries in CNS = no pores
- only lipophilic drugs can cross capillary membrane
- only lipophilic drugs can cross capillary membrane
- placenta good barrier
- only lipophilic drugs cross to foetus
- only lipophilic drugs cross to foetus
- Capillaries in CNS = no pores
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