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Pharmacology: Bioavailability sound on image

Introduction
 
Drug
Properties
 
Physiology
 
Medicine
Properties
 
Bioavailability
 
Activity
 
Assessment
 
Resources

Factor 2: Important physiological factors

Physiological factors that reduce the absorption of a drug include rapid intestinal transit time, reduced splanchic circulation (such as occurs in shock) and the presence of food in the stomach.

However, one of the most important factors is first pass metabolism - that is the extent to which the drug is destroyed on its first passage through the liver. If a drug is rapidly metabolised by the liver, the amount of active drug the reaches the systemic circulation will be reduced. Propranolol is one drug that is significantly transformed during a single pass through the liver whilst, if swallowed, glyceryl trinitrate (GTN) is rendered ineffective by first pass metabolism.

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Page created: 16 January, 2004
Last updated: 28 April, 2004 6:01 PM
By: Gareth Peevers, Mark Foss