Inclusion Criteria:

• Histologically confirmed diagnosis of a primary malignant brain tumor or, if metastatic, documentation and histology (if available) of primary source of cancer.
• Patient must have 1 or more qualifying steroid-associated side effect(s) at Baseline.
• Patient has required administration of dexamethasone to control symptoms of peritumoral edema for at least 30 days.
• Stable dexamethasone dose of 4-24 mg/day for at least 14 days prior to Baseline.
• Need for administration of dexamethasone to treat peritumoral brain edema (referenced above) has been documented by MRI or comparable diagnostic technology within 21 days of Baseline.
• Karnofsky score of > 50 at Screening and Baseline.
• Capable of self-administration of subcutaneous injections twice daily for 12 weeks, or availability of assistance from caregiver.
• Ability to provide written informed consent or, if unable to provide, have a legal guardian or representative provide written informed consent.
• For women of childbearing potential: a negative serum pregnancy test at Screening.
• Must be 18 years of age or older

Exclusion Criteria:

• Ongoing or anticipated need for surgery, radiosurgery or radiation therapy or the introduction of new chemotherapeutic regime within the first 5 weeks of study enrollment. Treatment with pre-study chemotherapy may continue.
• Concurrent enrollment in any other investigational drug or device study, or plan to enroll in such a study during the first 5 weeks of treatment.
• Systemic steroid use for any indication other than peritumoral brain edema.
• Use or intended use of dexamethasone as an anti-emetic during Screening or Study
• Non-compliance with dexamethasone or anticonvulsant therapy.
• Clinical signs and symptoms of cerebral herniation.
• Serious concomitant cardiovascular, pulmonary, renal, gastrointestinal or endocrine metabolic disease which could put the patient at unusual risk for study participation.
• Confounding previous or concurrent neurological disorders that would interfere with adequate clinical evaluation.
• Clinically significant head injury or chronic seizure disorder, if the condition results in functional impairment or is likely to interfere with evaluations. (Maintenance anticonvulsant therapy is allowed.)
• Central nervous system infection.
• Pregnancy, breastfeeding and/or refusal to practice birth control while in study, for women of childbearing potential.
• Any conditions that are considered contraindications for patients to receive niacin, e.g. liver disease (with LFTs > 3 times the upper limit of the norm),active peptic ulcer, arterial hemorrhage, asthma and known hypersensitivity to niacin.