(Disclaimer: Content provided below is for informational purposes only and does not constitute medical advice.)

Medicine has become compartmentalized and it is not necessarily a good thing. Physicians work in silos, so do pharmacists. Things are particularly worse in urban India where even patients have started viewing healthcare in pieces. Patients with multiple medical problems (especially elderly) see multiple doctors and happen to be on multiple medications. Recently, I have come across several patients on multiple medications (polypharmacy) and with potentially dangerous interactions.

As a family physician, I am always interested in learning how I can take care of my patients with least number of medications and in best case no medications. While there are several good initiatives (generic medicines/ family physician models/ use of Health information technology- EMR/mobile apps etc) that can be of help, being insightful is the first step to preventing dangerous drug interactions.

Definition: A drug interaction is a situation in which a substance (usually another drug) affects the activity of a drug when both are administered together. This action can be synergistic (when the drug’s effect is increased) or antagonistic (when the drug’s effect is decreased) or a new effect can be produced that neither produces on its own. (wiki)

Simply put, drug interactions can make the drug less effective, increase the effect of drug and at the worst can have serious life-threatening complications.

Drug interactions fall into three broad categories:

1.      Drug-Drug Interactions

2.      Drug-Disease Interaction

3.      Drug-Nutrient Interaction

Drug-Drug Interactions (DDI)

As is evident from the name, this kind of interaction happens when two or more drugs react with each other. In two studies done in tertiary setting in India, the rates of drug-drug interactions have been reported very high.

What are the risk factors for drug-drug interactions?

Polypharmacy (>5 medications), advanced age of patients, drugs with narrow therapeutic range, decreased kidney and/or liver function, co-administration (in some cases) and poor literacy/ health literacy are the common risk factors for DDIs. The risk for DDI increases exponentially with increasing number of medications.

In India, where the rates of self-prescription are high, it poses an additional risk.

How can we minimize the risk for severe drug-drug interactions?

Drug-Disease Interactions

Interaction between drug and existing medical condition: Although these can happen to any individual, they are common in elderly. Elderly are more likely to have medical conditions, impaired kidney and liver functions and multiple medications.

These kinds of interactions are easily preventable if doctors take a detailed history and list out all the medical conditions and patients provide the information accurately to their doctors.

Examples: Use of NSAIDS and cold medicines in patients with high blood pressure,                   Use of certain cold medicines can increase the eye pressure in glaucoma etc

Drug-Nutrient Interactions

As is evident from name, this type of interaction refers to the interaction between drug and nutrients. Nutrients include food, beverages and dietary supplements. Nutrients can affect the absorption of the drug and can also give rise to serious side-effects (For e.g. interaction of metronidazole with alcohol).

Many patients consume herbal products and do not know that these products can interfere with their medicines. There is a list of herb- allopathic drug interaction available on Maharashtra State Pharmacy Council’s Drug Information Center website.

Doctors and patients both have to play an important role in preventing drug interactions. A doctor’s job does not end at handing over a prescription to patient: He should make sure patient has understood why and how the medicine needs to be taken and inform the potentially serious side-effects. On the other hand, a patient’s responsibility is to take the medicine exactly as prescribed and communicate with his doctor if he hasn’t been able to adhere and the reasons there of. In the articles following, I will discuss more on problems with medication adherence, polypharmacy, Safe medication practices etc.

Please share any practical tips you have been using in your practice to avoid drug interactions.

Resources:

Medication Safety tools and Resources: Institute of Safe Medication Practices http://www.ismp.org/tools/

Medscape: Drug Interaction checker
http://reference.medscape.com/drug-interactionchecker

Herb Allopathic drug interactions: Maharashtra State Pharmacy Council
http://www.mspcindia.org/dic/menuLinks/Drugs.aspx

Drug Interactions: http://www.merckmanuals.com/home/drugs/factors_affecting_response_to_drugs/drug_interactions.html