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Toxic Drug Interactions You Need To Know About

Updated on February 26, 2020
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Healthy Living Since entering recovery from substance abuse in 2009, Cindy has been on a mission to live healthy & Holistically

From over-the-counter drugs, to drugs prescribed by a doctor, medications can help you live a happier, healthier life. However, all medications come with precautions. One precaution that is not often found on the label or package inserts is the food and beverages the drug may not be compatible with.

How Drugs Work In Your Body

Sometimes, the things we eat and drink everyday can interact with the medications we take. This can cause adverse reactions or simply prevent the medication from doing its job properly. The food itself or the nutrients in the food can cause an interaction. Either of these can prevent the medicine you take from working properly. At best, you may not get all the benefits the drug could provide, and at worst, it could prove to be harmful.

Once ingested, medications must go through four basic steps in order to be of any benefit to you. If any part of that process is interrupted, the drug can no longer do what it is supposed to do. This can render the drug totally ineffective or cause it to build up to toxic levels in your body. These four steps are:

  1. Oral medications must dissolve into a form the stomach can utilize.
  2. The stomach can then prepare the drug to be absorbed over time into the bloodstream and dispersed to the site in the body where it’s needed.
  3. The drug must be able to perform its intended function, once at the site
  4. Last, the unused portion of the drug must be expelled from the body

Each of the foods listed below interferes with some part of this process.

1) Milk

You should not drink milk while taking antibiotics. While milk is a rich source of Vitamin D, the calcium in dairy products makes it extremely difficult for your body to absorb antibiotics like those in the "cillin" family. Here are some to be aware of:

  • cephalexin (Keflex)
  • amoxicillin (Amoxil)
  • ciprofloxacin (Cipro)
  • clindamycin (Cleocin)
  • metronidazole (Flagyl)
  • levofloxacin (Levaquin)
  • amoxicillin potassium clavulanate (Augmentin)


Perhaps the most common food to watch out for is grapefruit juice. If you drink a lot of grapefruit juice, it might be a good idea to check each medication you take. This list is constantly being updated and revised, so if you find adverse interactions, your doctor may simply be able to switch you to a different drug that will treat the same thing.

Grapefruit juice contains something called furanocoumarin. This is an acid in the fruit that can react with liver enzymes and cause interference with the proper absorption of many drugs. If the enzyme is blocked, the drug can quickly reach toxic levels in the blood stream.

Seville oranges (often used to make orange marmalade) and Tangelos (a cross between tangerines and grapefruit) affect the same enzyme as grapefruit juice, so avoid these fruits as well if your medicine interacts with grapefruit juice. Any of these fruits or juices should be taken sparingly, 2-3 hours before or after your medication. Better yet, avoid them altogether with the following medications:


Statins are a class of drugs that are used to help treat high cholesterol. Many people with cardiovascular (heart) diseases may take statins, since high cholesterol is known to cause heart disease. If the statins can’t work properly, you may be at risk. Avoid grapefruit juice if you take any of the following:

  • atorvastatin (Lipitor)
  • lovastatin (Mevacor)
  • simvastatin (Zocor, Simlup, Simcor, Simvacor)

These statins are NOT affected by grapefruit juice:

  • Pravastatin (Pravachol)
  • fluvastatin (Lescol)
  • rosuvastatin (Crestor)


Benzodiazepines are commonly prescribed for anxiety, muscle spasms, insomnia, and agitation. They produce a sedating effect when used, and can be short-term or long acting. If they are not properly absorbed, they can build up to toxic levels causing heavy sedation and can be fatal. Avoid grapefruit juice if you take any of the following:

  • triazolam (Halcion)
  • midazolam (Versed) orally administered
  • triazepam (Mogodon) orally administered
  • diazepam (Valium)
  • alprazolam (Xanax)
  • quazepam[4]


Dihydropyridines may be taken to help control high blood pressure. Avoid grapefruit juice if you take any of the following:

  • felodipine (Plendil)
  • nicardipine (Cardene)
  • nifedipine
  • nisoldipine (Sular)
  • nitrendipine (Bayotensin)
  • Other drug that cannot be taken with grapefruit juice are:

The anti-anxiety drug

  • Buspirone (Buspar)

The anti-malaria drug

  • Quinine (Quinerva or Quinite)


Caffeine is a well known ingredient in coffee. But did you know that chocolate also contains high levels of caffeine? Many drugs will affect how the body is able to break down and process caffeine. This can cause a build-up of caffeine in the system causing nervousness, jitters, racing heart, headache and dizziness. Chocolate may also prevent some medications from working properly. It’s best to avoid chocolate if you take any of the following medications:


  • Precautions should be taken whenever a stimulant medication is taken, including
  • methylphenidate (Ritalin)
  • Provogil
  • amphetamine and dextroamphetamine (Adderall)

Diabetes medications including:

  • glimepiride (Amaryl)
  • glyburide (DiaBeta, Glynase)
  • insulin
  • pioglitazone (Actos)
  • rosiglitazone (Avandia)
  • chlorpropamide (Diabinese)
  • glipizide (Glucotrol)
  • tolbutamide (Orinase)

Asthma medications including:

  • albuterol (Proventil, Ventolin, Volmax)
  • metaproterenol (Alupent)
  • terbutaline (Bricanyl, Brethine)
  • isoproterenol (Isuprel)

Anti-anxiety medications and drugs to help you sleep better, such as:

  • Benzodiazapines prescribed for insomnia such as:
  • estazolam (brand name ProSom)
  • flurazepam (Dalmane)
  • quazepam (Doral)
  • temazepam (Restoril)
  • triazolam (Halcion)

Chocolate can also cause adverse reactions when taken with these drugs:

Estrogens can affect how the body breaks down and absorbs the caffeine in chocolate causing the jitters as well as a racing heartbeat and headache. The following are brand names of estrogen or estrogen combination drugs (Conjugated Estrogens, Meprobamate)

  • Premarin
  • Estratab
  • Enjuvia
  • CovaryxEssian
  • Estratest
  • Syntest
  • Femtest
  • Menogen
  • PMB
  • Premarin

Heart medications such as the following, which are prescribed when a cardiac stress test is needed. Chocolate can increase the heart rate and interfere with proper results

  • Adenosine (Adenocard)
  • Dipyridamole (Persantine)

Some anti-depressants can stimulate the body. Combined with the caffeine in chocolate, this could cause serious side effects including fast heartbeat, high blood pressure, nervousness, and others.

MAOI’s such as:

  • socarboxazid (Marplan)
  • Selegiline (Emsam, Eldepryl, Zelapar)
  • phenelzine (Nardil)
  • tranylcypromine (Parnate)
  • Iproniazid (Marsilid, Iprozid, Ipronid, Rivivol, Propilniazida)
  • Octamoxin (Ximaol, Nimaol)
  • Procarbazine (Matulane, Natulan, Indicarb)

Antibiotics, including the following, when taken with chocolate can also cause nervousness, anxiety, and nausea:

  • ciprofloxacin (Cipro)
  • enoxacin (Penetrex)
  • norfloxacin (Chibroxin, Noroxin)
  • sparfloxacin (Zagam)
  • trovafloxacin (Trovan)
  • grepafloxacin (Raxar)


Green leafy vegetables contain vitamin K, which is used to help clot blood. People who are on blood thinners should avoid eating too much of these vegetables. Green leafy vegetables, as well as bananas are high in potassium. Some medications can also increase the amount of potassium in your system. Too much potassium can be harmful and cause heart palpitations and rapid heartbeat. Talk with your doctor to decide how much, if any, is an acceptable amount if you take any of the following:

  • Warfarin (Coumadin)
  • Dicumarol
  • Anisinidione (miradon)
  • Heparin (Hep-Lock, Hep-Pak)
  • Enoxaparin (Clexane, Lovenox )
  • Dalteparin ( Fragmin )
  • Acetylsalicylic acid (Aspirin)
  • Bivalirudin (Angiomax, Angiox)
  • Clopidogrel bisulphate (Plavix)
  • Dipyramidole Aspirin dipyramidole (plavix)

ACE inhibitors-used in treating high blood pressure and heart failure-such as:

  • captopril (Capoten, Capozide)
  • enalapril (Vasotec)
  • lisinopril (Zestril, Prinvil, Zestoretic, Prinzide)
  • moexipril (Univasc)
  • quinapril (Accupril)
  • ramipril (Altace)

5) Aged Cheese

Aged cheeses such as parmesan, swiss, mozzarella, blue cheese, muenster, and gorgonzola contain tryramine which can cause high blood pressure when taken with the following:

MAOI’s(see partial list above)

  • Quinolones

Synthetic antibiotics-such as:

  • Ciprofloxacin (Cipro)
  • ofloxacin (Floxin, Oxaldin, Tarivid)
  • gatifloxacin (Zigat, Zymar-opth)


Some heart medications, including Diuretics which may be prescribed to reduce excess fluid caused by congestive heart failure, may also be affected and should not be taken if you eat licorice.

  • Digoxin (Lanoxin)
  • Hydrodiuril (hydrochlorothiazide)
  • Aldactone (spironolactone)


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