Interactions between food and drugs are important since it may influence success of drug treatment. The bioavailability of drugs depends on acid environment. That means amount of food and stomach acid do influence drugs absorption. Also the presence of minerals might interfere with absorption since some chemical complexes can form.
Both drugs and food are metabolized. Sometimes they compete for the same system of enzymes which influences clearance and effect of the medicine.
1. Anti-histamine drugs
a. Alcohol: increases sedative effect of anti-histamine drugs
b. Fruit: decreases bioavailability of fexofenadine
2. Painkillers
a. Alcohol: increases risk of liver damage
b. Food: delays analgesic action onset
3. NSAIDs
a. Alcohol: increases risk of stomach bleeding
b. Food: decreases stomach upset
4. Corticosteroids
a. Food: decreases stomach upset
5. Bronchodilators
a. Alcohol: increases risk of nausea, headache, irritability and vomiting
b. Fat: increases theophylline concentration
c. Carbohydrates: decrease theophylline concentration
6. Antibiotics
a. To be taken on empty stomach (1 hour before or 2 hours after meal):
Levofloxacin
Ciprofloxacin
Tetracycline
Minocycline
Doxycycline
These drugs do special interfere with calcium, magnesium, iron and diary products. Caffeine may lead to excitability and nervousness.
b. To be taken on empty stomach unless it causes stomach upset:
Penicillin
Amoxicillin
Cephalosporins
c. To be taken avoiding citrus and carbonated drinks:
Azithromycin
Clarithromycin
Erythromycin
d. To be taken with food and a big glass of water:
Sulfamethoxazole + trimethoprim
e. To be taken avoiding alcohol during and for 72h after the end of treatment:
Metronidazole
Alcohol intake can cause flushing, headache, nausea, vomiting, sweating and increased heart rate.
7. Antifungals
a. To be taken with food to increase absorption:
Griseofulvin
Ketoconazole
b. To be taken with food but avoiding grapefruit and citrus:
Itraconazole
c. To be taken with food but avoiding alcohol during and for 3 days after the end of treatment:
ketoconazole
Alcohol intake can cause abdominal cramps flushing, headache, nause and vomiting.
8. Anticoagulants
a. Foods high in vitamin K: reduce effectiveness of anticoagulants
b. High doses of vitamin E: prolong clotting time
Vitamin K influences coagulation process. Unbalanced diets might therefore interfere with anticoagulants.
Foods high in vitamin K like leafy green vegetables, some legumes and vegetable oils might reduce effectiveness of anticoagulants.
9. MAO inhibitors (isocarboxazid, phenelzine, tranylcypromine)
a. Foods high in tyramine: can cause a rapid, potentially fatal increase in blood pressure. To be avoided during and for 2 weeks after discontinuation of treatment
Alcoholic beverages high in tyramine - beer, ale, wine, vermouth
Legumes - bean curd, soya, broad beans
Diary products - aged cheeses
Smoked, fermented and pickled products like fish, liver, anchovies, sausages, pepperoni and salami
Sauerkraut
10. Antihypertensive drugs
a. Sodium intake: to be reduced since it increases blood pressure
b. Alcohol: to moderate since it may decrease blood pressure too much
10.1 Potassium sparing diuretics
a. High potassium foods: moderate consumption of bananas, oranges, green leafy and salt substitutes.
10.2 Beta-blockers
a. Food: increases bioavailability
b. Citrus: avoid with atenolol
c. Licorice: avoid with atenolol
10.3 Nitrates
a. Food: decreases absorption.
10.4 ACE inhibitors
a. Fat: decreases absorption of quinapril
10.5 Diuretics
a. Licorice: reduces diuretic effect
11. Antidislipidemia drugs
a. Grapefruit and citrus: reduce effect of statins
b. Alcohol: increases risk of liver damage
12. Levothyroxine
a. Food: decreases absorption
b. Iron: decreases absorption
13. Biphosphonates (alendronate, risedronate)
a. Food: decreases absorption
To be taken in the morning with a full glass of distilled water (not other drinks). Do not lie down. Wait at least 30 min before first meal and 1 or 2 hours before diary products intake.
14. Iron
a. Vitamin C: increases iron absorption
b. Calcium, zinc and copper: Decrease iron absorption
Absorption increased when taken on a empty stomach. If stomach upset is present recommend to take it after meal but avoiding cereals, fiber, diary products, coffee and tea.
15. Anti-Malaria drugs
a. Grapefruit juice: risk of toxicity due to blood level concentration increase
Lotus Pharmacy Education System Website
FDA poster
January 2019
Sara Silva
- Course creator: Lurdes Pastor
- Course creator: Eliana Sequeira
- Course creator: Molly WONG