nutrient drug interactions · 2013-09-08 · nutrient drug interactions effects of nutrition on...
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ESPEN Congress Brussels 2005
Nutrient Drug InteractionsEffects of Nutrition on Pharmacokinetics
and Pharmacodynamics of Drugs
Rebecca White
Nutrient Drug Interactions
Effects of Nutrition on Pharmacokinetics and
Pharmacodynamics of Drugs
Rebecca WhiteLead Pharmacist; Nutrition & Surgery
Oxford Radcliffe Hospitals, UK
Drug Nutrient Interaction
A pysico-chemical, physiological or pathophysiological process that alters disposition, function or toxicity of a food component or drug
• Absorption
• Distribution
• Metabolism
• Elimination
Absorption
Physiological Changes• Gut transit time• Intraluminal pH• Increased splanchnic blood flow• Decreased portal blood flow• Bile salt production• Competing or interfering with active
transport mechanisms
Absorption
Physico-chemical• Interaction affecting drug and feed physical
properties• Chelation
– Quinolones– Tetracyclines
• Binding to dietary substances– Protein– Fibre/pectin– Al & Mg salts
Distribution
• Malnutrition– Reduced plasma proteins– Increased total body water– Reduced fat stores– Reduced enzyme activity and substrate
availability
• Obesity
Metabolism
• Enzyme induction– High protein/low carbohydrate diet
• Enzyme inhibition– Grapefruit juice– MAOI’s
• Bacterial breakdown– Fibre/Protein source
• Malnutrition
Folate
• Folic acid is involved in DNA synthesis
• Deficiency causes:– Megaloblastic anaemia– Diarrhoea
• Folate metabolism
Dihydrofolate Tetrahydrofolate
Dihydrofolate reductase (DHFR)
Folic Acid
Folate Deficiency
• DHFR Inhibitors
• Methotrexate• Trimetrexate• Pentamidine• Proguanil• Pyrimethamine• Trimethoprim• Triamterene
• Impaired Absorption or Utilisation• Alcohol• Metformin• Nitrofurantoin• O.C.P• Phenobarbitone• Phenytoin (Carl, 1992)
• Primidone• Sulphasalazine (Pironi, 1988)
Thiamine (Vitamin B1)
• Deficiency causes Beri Beri– Lactic acidosis, cardiovascular, cerebral
and peripheral neurological impairment
• Drugs associated with thiamine deficiency– Frusemide (Seligmann et al, 1991)
Pyridoxine
• Co-factor for the transaminases and for decarboxylation of amino acids– Isoniazid– Phenelzine– Penicillamine– Oral contraceptive pill– Hydralazine– Phenytoin– Theophylline (Delport et al, 1988)
Elimination
• Increased clearance of electrolytes– Diuretics– Cisplatin– Amphoteracin
• Decreased clearance of electrolytes– Potassium sparing diuretics– Demeclocycline
Summary
• Complex array of interactions• Identification of high risk patients• Prevention/minimisation of interaction• Effective monitoring
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Neurology 32:570-575
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