Toremifene citrate (Fareston)

An estrogen agonist/antagonist indicated for the treatment of metastatic breast cancer in postmenopausal women with estrogen receptor positive or unknown tumors.

In clinical trials comparing this agent with tamoxifen: Response rates and median overall survival are similar,and they have similar efficacy in delaying time to progression of disease.

Response rates in trials range from 20-31%, median overall survivaltime 25-33 months, and median time to progression 4.9-7.3 months for postmenopausal women with metastatic breast cancer (North American trial, Eastern European trial, Nordic trial).

Activity not affected by CYP2D6 inhibition by co-administered drugs.

CYP2D6 variations a genetic status does not affect activity of the drugs.

Strong CYP3A4 inducers can lower the steady state concentration and include dexamethasone, phenytoin, carbamazine, rifampin, and phenobarbital.

Strong CYP3A4 inducers such as: Ketoconazole, itraconazole, clarithromycin,indinavir, nefazodone, nelfinavir, telithromycn, voriconazole, and grapefruit juice can increase the steady state concentration and should be avoided.

An effective alternative for patients who have had to discontinue endocrine therapy due to arthralgia.

Only 1 percent of patients discontinue toremifene because of adverse events.

Can prolonged QTc interval in a dose and concentration related manner, resulting in Torsade de pointes.

Should not be prescribed to patients with congenital or acquired QT prolongation, uncorrected hypokalemia or uncorrected hypomagnesemia.

Can cause fetal harm.

Most common adverse reactions are: Hot flashes, sweating, nausea, and vaginal discharge.

Dose: 60 mg tablets p.o. daily

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