Drug-Food Interactions
How food and beverages can affect medication efficacy and safety.
Overview
Drug-food interactions can:
- Alter drug absorption
- Change drug metabolism
- Affect drug distribution
- Impact clinical outcomes
Common Interactions
Grapefruit
One of the most clinically significant food-drug interactions.
| Drug Class | Examples | Effect |
|---|---|---|
| Statins | Simvastatin, Atorvastatin | Increased levels, myopathy |
| Calcium channel blockers | Felodipine, Nifedipine | Hypotension |
| Immunosuppressants | Cyclosporine, Tacrolimus | Toxicity |
| Antihistamines | Terfenadine | QT prolongation |
Mechanism: Inhibits intestinal CYP3A4 and P-glycoprotein
Dairy Products
| Drug | Effect | Recommendation |
|---|---|---|
| Tetracyclines | Reduced absorption | Separate by 2 hours |
| Fluoroquinolones | Reduced absorption | Separate by 2 hours |
| Bisphosphonates | Reduced absorption | Take on empty stomach |
Mechanism: Calcium chelation
High-Fat Meals
| Drug | Effect | Timing |
|---|---|---|
| Isotretinoin | Enhanced absorption | Take with food |
| Griseofulvin | Enhanced absorption | Take with fatty food |
| Some HIV drugs | Altered absorption | Check specific guidance |
Vitamin K Foods
| Foods | Drugs Affected | Clinical Impact |
|---|---|---|
| Green leafy vegetables | Warfarin | Reduced anticoagulation |
| Liver | Warfarin | INR variability |
| Green tea | Warfarin | Monitor INR |
Beverages
Alcohol
| Drug Class | Interaction |
|---|---|
| Metronidazole | Disulfiram reaction |
| Metformin | Lactic acidosis risk |
| Paracetamol | Hepatotoxicity |
| CNS depressants | Enhanced sedation |
| Antihypertensives | Hypotension |
Caffeine
| Drug | Interaction |
|---|---|
| Theophylline | Both metabolised by CYP1A2 |
| Fluoroquinolones | Inhibit caffeine metabolism |
| Lithium | Caffeine withdrawal increases levels |
Milk
See Dairy Products above.
Timing Recommendations
Take on Empty Stomach
(1 hour before or 2 hours after food)
| Drug | Reason |
|---|---|
| Bisphosphonates | Avoid calcium chelation |
| Levothyroxine | Maximise absorption |
| Some antibiotics | Food reduces absorption |
Take with Food
| Drug | Reason |
|---|---|
| NSAIDs | Reduce GI irritation |
| Metformin | Reduce GI side effects |
| Griseofulvin | Enhance absorption |
Special Diets
High-Protein Diet
- May affect L-dopa absorption
- Can alter drug binding
- May induce certain CYP enzymes
High-Fibre Diet
- May reduce drug absorption
- Can bind to certain medications
- Timing separation recommended
Enteral Nutrition
| Consideration | Action |
|---|---|
| Drug-formula compatibility | Check interactions |
| Timing of administration | Separate if needed |
| Tube occlusion | Use appropriate formulations |
Patient Counselling Points
- Consistency: Maintain consistent dietary habits with drugs like warfarin
- Timing: Follow specific timing instructions
- Grapefruit: Avoid with susceptible medications
- Alcohol: Check for interactions
- Supplements: Report all supplements to healthcare providers
Information Only
This information is for educational purposes. Patients should follow specific instructions from their healthcare providers and pharmacists regarding food-drug interactions.
This information is for educational purposes. Patients should follow specific instructions from their healthcare providers and pharmacists regarding food-drug interactions.