Drug Interaction Report

Using lefamulin together with toremifene is not recommended. Combining these medications 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). In addition, if you are using oral forms of these medications, an interaction could occur that results in increased blood levels of toremifene. You may experience increased side effects as a result. 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 either of these medications. 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 should avoid drinking grapefruit juice during treatment with toremifene. Grapefruit juice may increase the blood levels of toremifene. This can make you more likely to develop side effects such as vaginal bleeding, blood clots, or an irregular heart rhythm that may be serious or life-threatening. Contact your doctor if you experience potential signs and symptoms of blood clots such as chest pain, shortness of breath, sudden loss of vision, and pain, redness or swelling your arms or legs. You should also seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, or fast or pounding heartbeats during treatment with toremifene.

Talk to your doctor before using toremifene with soy products. There is some evidence that substances present in soy may stimulate breast tumor growth and interfere with the action of toremifene, although this has not been proven. Whether soy products are effective for hot flashes is also uncertain. 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.

The following interaction applies only if you are taking lefamulin (Xenleta) orally:

Food may interfere with the absorption of lefamulin, which may lead to lower blood levels of the medication and possibly reduced effectiveness. You should take lefamulin at least 1 hour before or 2 hours after a meal. It is best to avoid or limit the consumption of grapefruit and grapefruit juice during treatment with lefamulin, as it may increase blood levels of the medication and increase side effects. Talk to your doctor or pharmacist if you have any questions or concerns.