Are your drugs compatible?


Levothyroxine (Eltroxin and Synthroid) is used by people who have low thyroid hormone levels. Certain minerals can prevent levothyroxine from being absorbed and working properly in the body. So if you take a calcium or iron supplement, a multiple vitamin that contains calcium and iron or a stomach remedy that contains magnesium and aluminum (such as Maalox and Mylanta), wait four hours before taking levothyroxine.


If you are on an antidepressant such as paroxetine (Paxil) or sertraline (or Zoloft), it is important not to use St. John’s wort. A serious condition called serotonin-like syndrome may occur, which includes side effects such as dizziness, nausea, headache, tremors, anxiety, fever and confusion.

St. John’s wort can also decrease the effectiveness of the heart medication digoxin. Talk to your pharmacist to see if St. John’s wort is compatible with your present medications.


If you take medications to lower your blood pressure such as ramipril (Altace) or hydrochlorothiazide (Apo-Hydro), you need to be careful when using cough and cold preparations and some allergy medications.

These preparations may contain a decongestant (such as phenylephrine or pseudoephedrine), which elevates blood pressure. Talk to your pharmacist about what medication is right for you.


Many people are on alendronate (Fosamax) and risedronate (Actonel) to help strengthen their bones. Don’t consume food or take calcium or iron supplements or stomach remedies within two hours of these medications to allow ample time for the bone strengthener to be absorbed by the body.

The bottom line is that if you are on any prescription or non-prescription medication, consult with your physician or pharmacist before you add anything new. Make sure your physician and pharmacist know all the nonprescription medications you are on, including vitamins, minerals, herbal remedies, antihistamines and painkillers.

Report anything that is unusual to your pharmacist or physician when you start a new therapy. It could be the “new” medication is interacting with your present therapies.

Colleen Brady is a pharmacist in Vancouver and a lecturer in the faculty of pharmaceutical sciences at the University of British Columbia.

© May 2007 CARP magazine