Patients with brain metastases who require corticosteroids or non-enzyme inducing anticonvulsants must be on a stable dose of corticosteroids and seizure free for 1 month prior to enrollment; patients with known brain metastases should have completed brain irradiation (whole brain or gamma knife) more than 4 weeks before starting the protocol; patients on enzyme inducing anticonvulsants are not eligible; note that patients should have had their steroids tapered to low dose (i.e. < 1.5 mg of dexamethasone/day) due to the potential for higher dexamethasone doses to induce CYP3A4 Patients with gliomas or brain metastases who require corticosteroids or anticonvulsants must be on a stable dose of corticosteroids and seizure free for 1 month prior to enrollment; patients with known brain metastases should have had brain irradiation (whole brain or gamma knife) more than 4 weeks before starting the protocol; note that patients should have had their steroids tapered to low dose (i.e., < 1.5 mg of dexamethasone/day) Brain metastases that are symptomatic or requiring corticosteroids (except inhaled); subjects must also be off of enzyme-inducing anticonvulsants for > 4 weeks Patients must have no clinical evidence of leptomeningeal or brain metastasis causing spinal cord compression that are symptomatic or untreated or not stable for >= 3 months (must be documented by imaging) or requiring corticosteroids; subjects on a stable dose of corticosteroids > 1 month or who have been off of corticosteroids for at least 2 weeks can be enrolled with approval of the Cancer Therapy Evaluation Program (CTEP) medical monitor; subjects must also be off of enzyme-inducing anticonvulsants for > 4 weeks Patients must have no clinical evidence of leptomeningeal or brain metastasis causing spinal cord compression that are symptomatic or untreated or not stable for >= 4 weeks (must be documented by imaging) or requiring corticosteroids; subjects on a stable dose of corticosteroids > 1 month or who have been off of corticosteroids for at least 2 weeks can be enrolled with approval of the Cancer Therapy Evaluation Program (CTEP) medical monitor; subjects must also be off of enzyme-inducing anticonvulsants for > 4 weeks Leptomeningeal or brain metastases or metastases causing spinal cord compression that are symptomatic or untreated or not stable for >= 3 months (must be documented by imaging) or requiring corticosteroids; subjects on a stable dose of corticosteroids > 1 month or who have been off of corticosteroids for at least 2 weeks can be enrolled with approval of the Cancer Therapy Evaluation Program (CTEP) medical monitor; subjects must also be off of enzyme-inducing anticonvulsants for > 4 weeks