Factors Affecting Bioavailability Flashcards
Name some factors affecting bioavailability
Pharmaceutical factors
GI absorption
Presystemic metabolism
Factors affecting GI absorption
GI motility
Splanchic blood flow
Particularly size & formulation
Physiochemical factors
What can cause gastric stasis
Migraine
Particle formulations that can affect absorption
Tablet/capsule
Coating
Slow/fast release
Name a drug drug interaction
Tetracycline precipitates with calcium
I’m presystemic metabolism what is inactivated in gastric acid
Insulin
I’m presystemic metabolism what is metabolised in gut wal
Monoamines by MAO
Problems with transdermal
Multiple application a day
Differences in area of skin covered
Differences in thickness applied
What drugs are given transdermally
Ones with side effects
Ones that cause gastric irritation
Ones that require frequent dosing due to half life
Fastest and most certain route
Single bolus IV injection
100% bioavailability
What is advantage of steady IV infusion
Avoids high peak plasma conc
(Diazepam)
What is intrathecal
Injection into subarachnoid space via lumbar puncture needle
-aminoglycoside antibiotics
-local anaesthetics
What is inhalation advantageous
Direct delivery to site of action
Rapid action
Minimise systemic absorption
Minimise side effects
How much inhaled drug reaches airway
10-20%
How can u make an inhaled drug slow release
Liposome encapsulation
