Grapefruit & Singulair Interaction

It is unsafe to take certain medications with grapefruit or grapefruit juice as it can increase the potency of some drugs, sometimes to dangerously high levels. Unless otherwise advised by your doctor, however, there is no need to make dietary changes when you take the prescription medication Singulair to treat your asthma symptoms.

Identification

Singulair is a brand name for the drug montelukast. This drug is classified as a leukotriene receptor antagonist, or LTRA. It is used to treat asthma, seasonal allergies and exercise-induced bronchospasm. Leukotrienes are part of an inflammatory response by your body. Singulair inhibits the action of these compounds, which cause reactions in your body such as constricted airways and increased mucus secretion. It is not used to treat sudden attacks, however.

Grapefruit Factor

Interactions between grapefruit juice and drugs are of concern when the cytochrome p450 metabolic system is needed for the drug in your body. Also referred to as CYP3A, this system partially breaks drugs down in your intestines before the drugs are absorbed. Grapefruit interferes with this process, potentially causing higher drug concentrations to be released to your bloodstream. Despite the fact that it is an oral medication, no studies document an interaction between Singulair and grapefruit, according to the University of Florida. Other anti-asthma drugs do affect the CYP3A4 pathway, so check with your doctor for this interaction if you take a different type of LTRA.

Considerations

Singulair may be prescribed as an alternative to antihistamines in the case of seasonal allergies or year-round allergies. Some antihistamines, such as fexofenadine, have a strong interaction with grapefruit juice, notes MayoClinic.com. Like antihistamines, Singulair helps control allergy symptoms but does not cure them.

Warning

Singulair does not have any documented interactions with food, according to the American Academy of Family Physicians. Nonetheless, possible drug interactions need to be taken seriously. Make sure to inform your pharmacist and doctor of any vitamins, herbal products, nutritional supplements, nonprescription medications or prescription medicines you take. Be extra sure to inform your doctor if you take phenobarbital or rifampin because your may need to alter the dosage of your medication or more carefully monitor you for side effects.