drug absorption Flashcards
List the 4 main absorption routes via. the GI tract
Oral (most common
Buccal
Sublingual
Rectal
List forms of oral absortption
Solutions + suspensions
Tablets + capsules
Enteric coated tablet
Describe advantages of solutions and supsensions
Useful for the elderly, young and patients with swallowing difficulties
Extremely rapid absorption (small intestine most rapid)
What is a suspension
Coarse drugs in the liquid phase - good for unpalatable drugs
Give advantages of tablets and capsules
Convenient Stable Accurate dose Reproducable Mass production
Describe enteric coated drugs
Delayed disintegration of tablet until it reaches the small intestine
Can protect drug from the stomach acid OR protect stomach from drug eg aspirin
Describe and give advantages of the buccal/ sublingual routes
Ideal for drugs with extensive first pass metabolism
Dissolve slowly under tounge or buccal cavity eg. GTN for angina
Give advantages of the rectal route (suppository)
Useful in youg, old and those with difficulties swallowing
Treat local conditions
Achieve systemic absorption
Bypass first pass metabolism
Give advantages of injection based administration (IV, IM, subcutaneous)
Provide fast, systemic effects by passing first pass metabolism
Can be administered to the unconscious
Short half life so can be infused continuously
Give advantage and disadvantages of IV routes
Rapid onset
100% absorption
Can be toxic (give slowly, monitor plasma level)
Narrow therapeutic index
Describe Intramuscular administartion
Injection is given into muscle mass
Allows more sustained duration of action
NEVER use if abnormal clotting
Give advantages of subcutaneous injections
Easy for patient to use
No need for venous access
eg. insulin, heparin
Describe transdermal routes of adminstration
Adhesive pathways allow drug to cross skin surface by diffusion and go into systemic circulation by precutaneous absorption
Give examples of precutaneous routes
creams, ointments, patches
achieve local effects
What is the main advantage of skin patches
Controlled, sustained blood levels
eg. nicotine, contraception
Give advantages of inhalation administration
Drug delivered directly to action site (lung)
Rapid effect
Reduced adverse affects
However, patients must be educated.
Define prodrugs
Synthesised inactive derivatives of an active drug which is then activated metabolically after administartion
Give advantages of prodrugs
Prolongation of duration
Avoid degradation in the gut
Unpalatable drugs are made tasteless
Discuss the use of prolonged release drugs
Most disorders require prolonged therapy
This maintains drug levels within the therapeutic range and reduces need fro frequent dosing - patients comply & save staff time
How do prolonged release drugs work
Reduce rate of absorption of the drug - slower but sustained
Can use a more active form of the drug
