Doctors discover 58 new drug and supplement combinations you must NEVER take together – they could have deadly consequences for millions of Americans

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Written By Rivera Claudia

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Doctors have discovered nearly 60 common drug combinations that could be putting millions of Americans at risk of deadly complications. 

Taking popular medicines like the blood thinner warfarin with some antibiotics, or pairing blood pressure pills with turmeric supplements, could render life-saving drugs ineffective or result in a dangerous unintentional overdose.

It means at least 20 million Americans who rely on these heart disease meds could  be unwittingly putting themselves at risk of a deadly heart attack, stroke or major bleed.

The study, by researchers at the Massachusetts Institute of Technology, discovered a striking 2 million potentially-harmful interactions — 58 of which had not previously been documented.

Scientists warned that the antibiotic doxycycline, available on prescription, could interact with the drugs warfarin – a blood thinner – and tacrolimus – an immune system suppressor (stock)

Interactions detected included the antibiotic doxycycline, or Periostat, used to treat pneumonia and sexually transmitted diseases (STDs), and warfarin – prescribed to around 14million Americans with heart disease every year.

Avoid mixing these drugs, researchers say:

Avoid taking these drugs at the same time, the researchers say:

  • Ibuprofen (painkiller)
  • Warfarin (prevent blood clots, for heart disease patients)
  • Verelan, drug name Verapamil (for high blood pressure) 
  • Quinine (malaria medication)
  • Ergomar or Cafergot (Ergotamine D-tartrate, used for migraines)
  • Ranitidine (to reduce stomach acid)
  • Carbamazepine (epilepsy patients)
  • Atorvastatin (lower cholesterol)
  • Levetiracetam (antiseizure drug)
  • Tacrolimus (immunosuppressant)
  • Doxycycline (antibiotic) 

And these:

  • Turmeric supplements
  • Warfarin (prevent blood clots, for heart disease patients)
  • Quinine (malaria medication)
  • Doxycycline (antibiotic) 
  • Ergomar or Cafergot (Ergotamine D-tartrate, used for migraines)
  • Ranitide (to reduce stomach acid)
  • Curatil, Tegretol or Carbamazepine (epilepsy treatment)
  • Nadolol (high blood pressure drug)

…And these:

  • Atrovastatin (to lower cholesterol) 
  • Lasix or Furosemide (treat high blood pressure)
  • Ergomar or Cafergot (Ergotamine D-tartrate, used for migraines)
  • Ranitidine (to reduce stomach acid)
  • Migranal, DHE or Di-hydroergotamine (for migraines)
  • Doxycycline (antibiotic) 
  • Digoxin (a heart failure medication)

The drugs have been split by which transporter protein in the gut that they use to enter the body. 


Combinations of the heart failure medication digoxin, the anti-seizure drug levetiracetam and immunosuppresant tacrolimus were also found to be risky.

Specifically, either a drug is super-metabolized, meaning patients receive a higher dose than they need, or it is under-metabolized, meaning they get too little.

The researchers explained that the problem lies wih the way in which the drugs are processed by the body.

All oral medication is metabolized via one of just a few specialist transporter proteins in the intestines.

Sometimes, medications compete for the same transporter proteins — so patients receive too little of a drug. In some cases, this means patients receive too high a dose.

For the study, published in the journal Nature Biomedical Engineering, researchers looked at 23 commonly used prescription and over-the-counter drugs, as well as 28 drugs less commonly used medicines – and more than a thousand experimental drugs.

They exposed each of the drugs to cells from a pig’s intestine, to simulate how the medicine would be metabolized in the human body.

They blocked one of three transporter proteins in the cells,  and monitored how much of the drug remained in the tissue.

If very little of the drug was detected, this revealed the transporter protein that it used.

The researchers fed the data into a machine-learning model to compute which drugs would likely be using the same transporter.

It predicted nearly 2 million interactions, including 58 that were previously unknown.

In a second part of the study, researchers examined blood test data from 50 patients who were prescribed doxycycline.

Each had previously been taking warfarin, digoxin, levetiracetam or tacrolimus.

The results showed that patients on warfarin got a ‘super dose’ of the drug when it was given alongside doxycycline.

Too much warfarin can stop the blood being able to clot, raising the risk of gastrointestinal bleeds, nosebleeds and bleeds under the skin.

Dr Traverso added: ‘These are drugs that are commonly used, and we are the first to predict this interaction using this accelerated in silico and in vitro model.

‘This kind of approach gives you the ability to understand the potential safety implications of giving these drugs together.’

Dr Giovanni Traverso, a gastroenterologist who was involved in the study, said: ‘One of the challenges in modeling absorption is that drugs are subject to different transporters.

‘This study is all about how we can model those interactions, which could help us make drugs safer and more efficacious [work better].

‘[It could also help us to] predict potential toxicities that may have been difficult to predict until now.’

Experts suggest that patients should wait several hours — typically four to six hours —  between taking the above medications to reduce the risk of interactions.



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