Do You Know How To Take Your Prescriptions?

A Q&A with George Zahalan, pharmacist/owner of CentreTown Pharmacy

Prescription symbol RxPharmacists

Can you explain the role of a pharmacist in health care?

Pharmacists are drug therapy experts in the health care team, including a heavy focus on reviewing prescriptions for therapeutic appropriateness, medication reconciliation, medication reviews, developing care plans, and monitoring health endpoints (cardiac, neurological, etc.) with medications prescribed.  We also identify drug therapy problems like drug interactions, contraindications (when you cannot take a medication), etc.  Recently we have also had our scope of practice expanded so it includes administering vaccines and, in some provinces (not Ontario sadly), prescribing medication for minor ailments (cold sores, etc.) that you would normally see a doctor for and ordering lab tests.

As a pharmacist, what do you wish people know about taking prescription medications?

I wish they knew how much work goes into what pharmacists do.  People think it’s as simple as getting the prescription from the doctor/prescriber and putting them in bottles and packages.  It is not that, whatsoever.  As a pharmacist, we first need to ensure that the we get the medication order and that we interpret it correctly.  The next step is to make sure that the medication is going to be safe and effective for the patient.  This is the hardest step because it is based on so many factors like other medications that patient is taking (i.e. drug interactions), what age they are, what allergies they have, what diet they have, what exercise they do, if they smoke or drink alcohol, how their metabolism is (i.e. kidney and liver function) etc.   The next step is actually providing that medication and giving as much instruction to the patient as possible in an easy-to-understand format without forgetting anything… Oh, and we need to do this is 15 minutes or less because of how impatient some people are!

[There may be errors] made by the doctor/prescriber as well so we need to clarify those before we give something wrong or harmful to the patient.

There is definitely a lot that goes into being a pharmacist and at Centretown Pharmacy, we pride ourselves on doing it in the best and most compassionate ways possible!


Common food/drug interactionsInteractions

Can you explain to us what drug interactions are? 

A drug interaction is a change in the action or side effects of a drug caused by [taking prescriptions at the same time (or close to)] a food, beverage, supplement, or another drug. There are many causes of drug interactions and many outcomes.  A drug-drug interaction can delay, decrease, or enhance absorption of either drug. This can decrease or increase the action of either of both drugs, or cause adverse effects.

Can you give some examples of over-the-counter drugs and supplements which can negatively interact with prescription medications?

There are some big culprits here, even ones that you may use on an often-enough basis!  Any cough syrup or medication containing dextromethorphan (DM) which is basically almost all of them (Benylin, Dimetapp, Tylenol Cold and Sinus, Tylenol Flu, etc.) interacts with several HIV medications, anti-depressants/mood stabilizer medication, anti-anxiety agents, insomnia drugs…

Anti-inflammatories such as Advil, Aleve, Motrin, etc. may interact with your heart medication.  So if you’re taking anything for heart disease (atrial fibrillation, hypertension, stroke prevention, etc.) you really have to try and avoid anti-inflammatories at all cost.

Tylenol (acetaminophen) – this common one can interact with blood thinners like Warfarin which could put you at risk of heart attacks and strokes.  It also is quite taxing on the liver so anyone who has Hepatitis C (liver disease), Hepatitis A or B (different liver diseases), alcohol-induced Hepatitis, or has a chronic history of alcohol use should avoid Tylenol at all costs.

St. John’s Wort – this is an herbal anti-depressant that has become popular in the last 20 years.  It is a terrible drug in that it can negatively affect many medications.  It speeds up your body’s liver metabolism so other medication you take may not have any effect at all or may have too powerful an effect.  Stay away from St. John’s wort!

There are many [over-the-counter drugs] and supplements that can interact with food – as always please consult your pharmacist and doctor before taking anything.

Can certain foods/beverages impact the effectiveness of certain medications?

Absolutely!  A common food/beverage that interacts is grapefruits and grapefruit juice!  They act on the liver and can slow down the metabolism of some drugs.  That makes the medication you take stay in your system for much longer than it should, which in turn gives you more side effects!

There are also certain [minerals] such as calcium, iron and magnesium that can affect how a medication (ex: HIV medication, thyroid medication and others) gets absorbed into a person’s body.  This can decrease how much of the medication actually makes it into your system leading to treatment failure.

Make sure to ask these questions to your pharmacist – they should have already notified you but if not, you need to seek this information out.

What are possible signs/symptoms that a food or drug is interacting negatively with one’s medications?

Generally, the way someone will know if there is an interaction taking place in their body is if they have no effect of the medication or if there is too much effect of the medication (so they are having toxicity/side effects).

What should a patient do if they experience a drug interaction?

Depending on the severity, they should either go to the hospital, call 911, call the pharmacy or their doctor.  Never use online resources or search engines to assess the severity.  Talk to a professional!

What is the best way for patients to avoid a drug interaction?

The best way is prevention – when you get a new prescription, make sure your pharmacist is giving you the information and, if not, make sure to ask for it.  At the end of the day, you must vouch for your own health and well-being.

What are some foods/beverages/supplements that someone taking HIV medications should never consume?

This is a complex question.  There are dozens and dozens of different HIV medications and combination pills so each one is different.  Some culprit foods and supplements of drug interactions with HIV medications include: Grapefruits and grapefruit juice, magnesium-containing food and supplements, calcium-containing food and supplements, iron-containing food and supplements, any acid-lowering supplements (Tums, Rolaids, Zantac, Pepcid, etc.), St. John’s wort, milk thistle, and several other foods and drinks and supplements may play a part.

Also, depending on which combo HIV pill someone is on, they need to either take it with food or not.  generally speaking:

    • Atripla – empty stomach at bedtime; avoid after high-fat meal to reduce side effects
    • Combivir (lam/zid) – with or without food
    • Descovy – with or without food
    • Eviplera – with food
    • Genvoya – with food
    • Kivexa – with or without food
    • Stribild – with food
    • Triumeq – with or without food
    • Trizivir – with or without food
    • Truvada – with food


Drug PackagePrescription Adherence

Why might someone not take their medications as prescribed?

This is a tough question.  There are so many reasons.  It could be someone’s mood, how busy they are, how forgetful they are, taking so many medication that they forget some or all, feelings of self-worthlessness or being ashamed, peer pressure to avoid the medication, not getting the medication use explained properly by their doctor and/or pharmacist, and not using compliance aids and packages from the pharmacy

Why is medication adherence important?

Medication adherence is important so that patients can get better from whatever disease or illness they have.  If they don’t take their medications as prescribed, they can get much sicker.  For people with HIV, medication adherence is especially important not only to keep your viral load down and your CD4 counts in a good range, but it is also important to avoid drug resistance.  Medication resistance is basically where the HIV virus learns how to overcome the medication you’re taking (because you’re not taking enough or properly) and more of the virus that has learned how to overcome the medication starts surviving (survival of the fittest!).

What can patients do that can help them easily adhere to a medication schedule?  What can a pharmacist offer to help?

At Centretown Pharmacy, we have several different compliance aids and we also keep people on schedule by reminding them when they’re due, automatically filling the medication and calling/reminding them, and delivering anywhere in the city!  We have dispills, med cards, and even customizable bags called sachets which has all the information on it you need (similar to those in a hospital).  Our dispill and sachet options are awesome because you can tear off the package you need for that day and bring your medication discreetly wherever you go.


  • Replies were edited for clarity.
  • CentreTown Pharmacy is a Bruce House partner and provides a counsellor for our Mental Health Program.