The staff at Vivian Pharmacy are passionate about Pharmaceutical Care. Our mission is to provide our patients with the best pharmaceutical service by ensuring they are well supported in taking their medications effectively and safely.We have a team of clinically orientated pharmacists and pharmacy technicians who are always happy, in addition to medication supply, to answer drug questions, counsel patients and provide medication education. Over the next few months we will be writing a series of articles that show you how interesting and often complex it is to ensure safe and effective pharmaceutical care. For the first article in the series we will discuss a question that we get asked very often; “Why must I avoid grapefruit with some medications?’
Words by Ger Jones, pharmacist
Combining grapefruit with some medications can be dangerous. The potential of grapefruit to interact with certain medications was accidentally discovered in the 1990’s with the blood pressure pill felodipine. This drug, which is a very useful drug for managing high blood pressure, was found to interact with grapefruit resulting in patients having severely low blood pressure. Since then more than 85 drugs have been identified to have the potential to cause serious adverse reactions when taken with grapefruit.
So what is the science behind this? Grapefruit contains chemicals called furanocoumarins, which block an enzyme that normally breaks down certain medications in the body. This can cause medication levels to increase to dangerous levels in the body (that is, more ‘active’ drug to be present in the body than was intended with the prescribed dose). One whole grapefruit or 200ml of juice can be sufficient to cause enough of an increase in the concentrations of active drugs to be unsafe.
The list of drugs affected by this phenomenon includes some essential drugs such as some statins that lower cholesterol, some antibiotics, cancer drugs, and heart drugs.
Here are two examples of how serious this interaction can be:
A form of abnormally rapid heartbeat (Torsade de pointes) has been reported when the drug amiodarone was taken with grapefruit. A breakdown of muscle fibres which leads to substances that can damage the kidney (Rhabdomyolysis) has been reported when certain statin drugs were taken with grapefruit
So how can you stay safe?
• When being prescribed a new medication, discuss with your doctor or pharmacist whether there are any foods or drinks you should avoid with your medication.
• Read the patient information leaflet that comes with your medicine, and follow the instructions for how it should be taken and what foods should be avoided.
• Never stop taking prescription medication without first talking to your doctor.
Your Doctor should be consulted before taking any drug, changing any diet or commencing or discontinuing any course of treatment.