Drug Interaction Report

Zafirlukast may increase the blood levels of halofantrine. High blood levels of halofantrine can increase the risk of an irregular heart rhythm that may be serious and potentially life-threatening, although it is a relatively rare side effect. You may be more susceptible if you have a heart condition called congenital long QT syndrome, other cardiac diseases, conduction abnormalities, or electrolyte disturbances (for example, magnesium or potassium loss due to severe or prolonged diarrhea or vomiting). Talk to your doctor if you have any questions or concerns. Your doctor may be able to prescribe alternatives that do not interact. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or heart palpitations during treatment with halofantrine. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

You may experience reduced absorption of halofantrine in the presence of food. Halofantrine should be taken on an empty stomach at least 1 hour before or 2 hours after food. This will make it easier for your body to absorb the medication. Also, while taking halofantrine, you should avoid grapefruits and grapefruit juice. Grapefruit can raise the levels of halofantrine in your body and lead to increased adverse effects. Do not increase or decrease the amount of grapefruit products in your diet without first talking to your doctor.

Zafirlukast should be taken on an empty stomach 1 hour before or 2 hours after a meal unless otherwise directed by your doctor. You may experience reduced absorption of zafirlukast in the presence of food. This will make it easier for your body to absorb the medication.