Symfi and Vfend

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.

Using voriconazole together with efavirenz can alter the blood levels and effects of both medications. Specifically, voriconazole levels may decrease, which may make the medication less effective in treating your fungal infection. At the same time, efavirenz levels may increase, and you may experience more frequent and/or severe side effects. Talk to your doctor if you have any questions or concerns. Your doctor may already be aware of the interaction, but has determined that this is the best course of treatment for you and has taken appropriate precautions and is monitoring you closely for any potential complications. Contact your doctor if your conditions worsen or you have increased side effects of efavirenz such as nausea, vomiting, diarrhea, dizziness, insomnia, difficulty concentrating, abnormal dreams, depression, suicidal thoughts, and hallucinations. 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.

CONTRAINDICATED: Coadministration of efavirenz and voriconazole may significantly reduce the plasma concentrations of voriconazole and increase the plasma concentrations of efavirenz. The mechanism involves efavirenz induction of voriconazole metabolism via CYP450 2C19, 2C9 and 3A4, and voriconazole inhibition of efavirenz metabolism via CYP450 3A4. In healthy male subjects, administration of voriconazole (400 mg orally every 12 hours for 1 day, then 200 mg every 12 hours) with efavirenz (400 mg orally once a day) for 9 days decreased the steady-state voriconazole peak plasma concentration (Cmax) and systemic exposure (AUC) by an average of 61% and 77%, respectively. Conversely, voriconazole increased the steady-state Cmax and AUC of efavirenz by an average of 38% and 44%, respectively. When adjusted dosages of voriconazole (300 mg orally every 12 hours) and efavirenz (300 mg orally once a day) were coadministered for 7 days, mean voriconazole Cmax was reduced by 36% and AUC by 55%, while mean efavirenz Cmax was reduced by 14% and AUC not significantly affected. In contrast, when voriconazole dosage was increased to 400 mg orally every 12 hours and coadministered with efavirenz (300 mg orally once a day) for 7 days, the changes in Cmax and AUC of each drug were not considered clinically significant relative to steady-state administration of voriconazole or efavirenz alone at their normally recommended dosages. Clinically, the interaction may result in voriconazole treatment failure. In one case report, a 50-year-old HIV-infected male developed breakthrough Candida esophagitis during treatment with an antiretroviral regimen that contained efavirenz 600 mg/day and voriconazole 200 mg orally twice a day for invasive pulmonary aspergillosis. A dosage increase of voriconazole to 350 mg twice daily was required. The concomitant use of intravenous voriconazole and oral efavirenz has not been studied.

MANAGEMENT: Concomitant use of standard dosages of voriconazole with efavirenz dosages of 400 mg every 24 hours or higher is considered contraindicated. If concurrent administration is necessary, the manufacturer recommends that maintenance dosage of voriconazole be increased from 200 mg to 400 mg orally every 12 hours and that of efavirenz be reduced from 600 mg to 300 mg orally once daily. When treatment with voriconazole is stopped, the initial dosage of efavirenz should be restored (and vice versa). No dosage recommendations are available for the concomitant use of intravenous voriconazole and oral efavirenz.

Symfi

Generic Name: efavirenz / lamivudine / tenofovir

Brand name: Symfi, Symfi Lo

Synonyms: n.a.

What is Symfi?

Vfend

Generic Name: voriconazole

Brand name: Vfend, Vfend

Synonyms: Vfend Injection

What is Vfend?