Grapefruit can cause drug reactions. But grapefruit is not the only fruit that reacts with drugs… other fruits with digestive enzymes also cause drug reactions:

pineapple-papaya-mango-mange-strawberries-kiwi-grapes-ginger-mustard-coriander-aloe vera-etc and citrus fruits: oranges lemons limes and grapefruit

Chemical additives can also cause drug reactions:
Meat tenderizers (sodium phosphates)… found in processed meat and fish… and in processed foods and snacks.
Bread tenderizers… in commercial bread (soft breads)
Lact-Aid… lactase
Lactase lipase invertase etc… and digestive enzyme supplements

Digestive enzymes and chemical tenderizers cause drug reactions… ADR Adverse Drug Reactions… strong chemical reactions that cause tissue and organ damage.
Can cause severe heart damage… and also liver and kidney damage (chemical burn).

The above foods and chemical additives can cause ADR adverse drug reactions… with Rx drugs and antibiotics (except penicillin and amoxicillin)… and ibuprofen.

When you have a severe drug reaction, you need to see a medical doctor.
Because it makes you sick… very sick.

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Example 1: quinlones react with pineapple, and possibly other foods with DE digestive enzymes. Causes inflamed enlarged heart (severe heart damage).
Example 2: ibuprofen + meat tenderizer (sodium phosphate) in tuna, French Fries and potato chips etc = causes heart damage… severe chemical burn… the heart feels like it has been fried in a frying pan

Treatment:
Can use Apple Juice to stop drug reactions… or vitamin C ascorbic acid

Treatment for inflammation (chemical burn):
For severe inflammation… use honey oatmeal slippery-elm and tea… twice daily
To repair organ damage… use extra protein and ice-cream (contains carrageenan).

After meals and before bed… use oat milk… and cocoa or chocolate
And you start to feel better within 1 month.

When using antibiotics and ibuprofen, you need to follow a bland diet to prevent drug reactions.

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For more information about treatment see the following articles:
Natural Heart Care
Medicinal Uses of Seaweed gelatin: agar and carrageenan
Ice-cream is good for cancer patients…
Medicinal Uses of Honey
Health Benefits of Oats
Medicinal Uses of Cocoa
Coffee and Cocoa