Page 78 - COMMUNITY PHARMACY PRACTICE
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• PHARMACOLOGICAL OR PHARMACOKINETIC. (ADME)
• The pharmacological interactions are the easiest ones to predict and respond
to, e.g. one would expect the actions of a β2-adrenocep- tor agonist for
asthma to be opposed by the concurrent use of a β blocker.
• Absorption
Absorption reactions may result in a change in either the rate of drug absorption
or the total amount of drug absorbed. (gastric motility, acid suppression…)
• Metabolism
hepatic metabolism , Alterations in drug metabolism can occur via the induction
or inhibition of cytochrome P450-dependent enzymes **
Renal excretion
Mechanisms of interactions
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Summary of some key interactions
• NSAIDs and warfarin: leading to enhanced bleeding
NSAIDs and methotrexate: leading to metho- trexate
toxicity
• warfarin and erythromycin: leading to en- hanced bleeding
• ACE inhibitors and potassium/potassium- sparing
diuretics: risk of hyperkalaemia
• verapamil and β blockers: risk of asystole
• digoxin and amiodarone: risk of digoxin
• toxicity
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