Fosamprenavir and Vemurafenib

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Talk to your doctor before using fosamprenavir together with vemurafenib. Combining these medications may decrease the blood levels of fosamprenavir, which may reduce its effectiveness in treating your condition. At the same time, fosamprenavir may cause the blood levels of vemurafenib to rise. This may increase the risk of an irregular heart rhythm that may be serious, as well as other side effects of vemurafenib. You may need a dose adjustment or more frequent monitoring by your doctor to safely use both medications. You should seek immediate medical attention if you develop sudden dizziness, lightheadedness, fainting, shortness of breath, or fast or pounding heartbeats during treatment with 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.

MONITOR: Coadministration with potent inhibitors of CYP450 3A4 may increase the plasma concentrations of vemurafenib, which has been shown in vitro to be a substrate of the isoenzyme. Because vemurafenib is associated with concentration-dependent prolongation of the QT interval, increased levels may potentiate the risk of ventricular arrhythmias such as torsade de pointes and sudden death. However, clinical and pharmacokinetic data are currently lacking. A reverse interaction may also occur, since many CYP450 3A4 inhibitors are also substrates of the isoenzyme and vemurafenib is an inducer. The possibility of diminished pharmacologic effects of these agents should be considered during coadministration with vemurafenib.

MANAGEMENT: Caution is advised if vemurafenib is prescribed in combination with potent CYP450 3A4 inhibitors such as itraconazole, ketoconazole, voriconazole, nefazodone, delavirdine, protease inhibitors, and ketolide and certain macrolide antibiotics. ECG and serum electrolytes, including potassium, magnesium and calcium, should be monitored regularly, and treatment interrupted if QTc exceeds 500 ms. Any electrolyte abnormalities must then be corrected and cardiac risk factors for QT prolongation (e.g., congestive heart failure, bradyarrhythmias) under control prior to resuming treatment. Vemurafenib may be restarted once QTc decreases below 500 ms, but at a reduced dosage as described in the product labeling. Permanent discontinuation of treatment is recommended if, after correction of associated risk factors, both the QTc is greater than 500 ms and the QTc increase is greater than 60 ms from pretreatment values. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, irregular heartbeat, shortness of breath, or syncope. In addition, many CYP450 3A4 inhibitors are also substrates of the isoenzyme, thus pharmacologic response to these agents should be monitored during coadministration with vemurafenib.

Fosamprenavir

Generic Name: fosamprenavir

Brand name: Lexiva, Telzir

Synonyms: n.a.

What is Fosamprenavir?

Vemurafenib

Generic Name: vemurafenib

Brand name: Zelboraf

Synonyms: n.a.

What is Vemurafenib?