1.5 food-drug interactions

Question 1

Please give examples of unspecific food drug-interactions

Answer 1

Unspecific: effects on absorption rate like degree of stomach filling affecting tmax and cmax, but total absoprtion is the same

• -> quick onset with empty stomach
• -> effect on enteric coating of sustained release drugs
• -> can lead to dose dumping and higher gastric ADRs

Question 2

What is the mechanistic background of dumping effect of sustained-release drugs that is caused by food drug-interactions?

Answer 2

For example when taking a retard tablet with fatty food: tmax decreased and cmax increased due to faster dissolution of the tablet. (diclofenac, ASS)

Coating that should avoid gastric damage may be damaged by pH increase due to food (PPI, digitoxin)

Drugs that contain acid-labile drug compounds loose their efficacy when the coating dissolves due to pH increase of food

Question 3

Please give some reasons why specific drug therapies should be intentionally applied together with food?

Answer 3

To reduce ADR like nausea (in allopurinol/gout therapy, iron)

To reduce ulcerogenic ADR (NSAIDs, glucocorticoids)

To minimise drug residues in oral cavity (in drug via inhaler like asthma/COPD therapy) –> oral mycosis

To increase BA of lipophilic drugs (HIV drugs, cancer therapy)

To improve digestive function(enzyme supplements like lactase..)

Question 4

Which combinations of food compounds and drugs can lead to formation of complexed, causing impaired drug bioavailability? How can you prevent such interactions in daily life?

Answer 4

Antibiotics (norfloxacin with milk), antidepressants (mapratiline with green tea), biphosphonates, iton and l-thyroxin can form complexes with ions (Ca, Mg), tannoids and casein in dairy, mineral water and tea/coffee

Take the drug 2-3h after food

Question 5

Please explain in detail the mechanistic background of drug interactions with grapefruit products. How relevant are resulting interactions, and by which means can they be prevented?

Answer 5

Grapefruit: Inhibits CYP3A4 which play a role in 30% of all drug metabolisms

• -> increased absorption and toxicity of drugs that are subject to CYP3A4 metabolism, eg suizide inhibtion of simvastatin (massive increase in cmax)
• -> as the effect persists 20-30h grapefruit products should be avoided in general

Question 6

Which drug classes are subjects to relevant interactions with alcohol. What are the pharmadynamic details?

Answer 6

Alcohol can lead to enzyme inhibition (drinking occasionally) or enzyme induction (drinking regular)
Effects on drugs due to:
-Increased perfusion of intestinal mucosa–> increased drug absorption
-Mucosa irritation –> ulcer risk increased due to eg. NSAIDs
-Hepatic damage: increased toxicity of drugs like paracetamol, MTX
-Inhibition of hepatic gluconeogenesis –> hypoglycemia, adopt diabetes medication

EtOH is a GABAa agonist and NMDA antagonist: alcohol increases drug effects like sedation, respiratory depression (from drugs like antidepressants, anticonvulsants, antihistamines, opioids)

Question 7

Which drug effects can be caused by dietary fibres?

Answer 7

Dietary fibers:

• speed of drug absorption decreased (tmax decreased), BA constant
• in certain drugs decreased BA (statins, l-thyroxin)

Question 8

Which drug effects can be caused by fatty food?

Answer 8

Fatty foods:

• Incerased BA of lipophilic drugs (beta-blockers like propranolol, antifungals),
• Reduced BA of hydrophilic drugs (beta-blockers like atenolol, celiprolol)
• Stimulation of bile production/secretion (incerased BA and solubility of hardly soluble drugs)

Question 9

Which drug effects can be caused by protein-rich food?

Answer 9

Protein-rich food:
-Interaction with levodopa (DOPA for Parkinson)
competing with AA at jejunal transporters, AA inhibit levodopa transport through BBB -> less levodapa in brain
- precautions: take drug 60 min prior to food and not togetehre with dairy products, but a low-protein diet is not necessary

Question 10

Please give examples of group-specific interactions

Answer 10

Group-specific: Effects with milk/dairy (Ca2+), mineral water (Ca2+, Mg2+) (eg antibiotics(norfloxacin), antidepressants, l-thyroxin), fatty foods, dietary fibers, proteinrich-foods

Question 11

Please give examples of specific food drug-interactions

Answer 11

Specific:

• Grapefruit products with eg simvastatin –> inhibit intestinal CYP3A4
• Tyramine-rich food with Monoaminooxidase-Inhibitors (MAOI) –> unselective, irreversible MAOI = tranycypromin
• High Vit K foods –> anticoagulants of coumarin type
• Liquorice (Glyzhrrhizin) inhibtis the reaction from cotrisol to the inactive cortison therefore leading to hyigher blood pressure
• alcohol effects liver enzymes and increrases perfusion through mucosa –> increased BV or ADRs
• red yeast rice: interaction with CPYs as it acts lika a statin

Question 12

Please explain in detail the mechanistic background of drug interactions with vitamin K-rich food. How relevant are resulting interactions, and by which means can they be prevented?

Answer 12

High Vit K: Interactions with anticoagulants of the coumarin type like Macumar (Macumar inhibits the Vit-K dependent synthesis of clotting factors 2, 7, 9, 10),
Increased Vit K in blood –> decreased anticoagulant effect (antagonism)

prevention: control Vit. K status and keep a constant diet

Question 13

Please explain in detail the mechanistic background of drug interactions with liquorice. How relevant are resulting interactions, and by which means can they be prevented?

Answer 13

Liquorice: contains glyzyrrhizin –> via hydrolysis to gyzyrrhetic acid –> inhibits 11-beta HSD (important for activation of glucocorticoids)
and important for deactivation of cortisol in body
–> leads to hypertension and therefore decreases the effect of antihypertensice medication

Question 14

Please explain in detail the mechanistic background of drug interactions with tyramine-rich food. How relevant are resulting interactions, and by which means can they be prevented?

Answer 14

Tyramine-rich food: MAOs normally degrade thyramine. If this is not the case thyramine is converted into norepinephrine which can e.g. cause high bloodpressure
Some drugs act likeMonoaminooxidase-Inhibitors (MOAI) e.g. Antidepressants–> unselective, irreversible MAOI = tranylcypromin (potentially life-threatening) compared to selcetive MAOAi (moclomebide) which are only critical and MAOBI which are less critical
–> prevention though thyamin los diet (tyrosine low)

Question 15

Please explain in detail the mechanistic background of drug interactions with red yeast rice. How relevant are resulting interactions, and by which means can they be prevented?

Answer 15

Red yeast rice: Fermented rice with monascus purpureus –> contains monacolin K (similar to lovostatin)
Subject to usual stain CYP interactions (substrate for CYP3A4) –> potent drug without control of potency, no food!