Safety and Tolerability of Phenylbutyrate in Inclusion Body Myositis

Inclusion Criteria: * Fulfill ENMC 2011 diagnostic criteria for IBM * Age \> 18 years * Women must be post-menopausal (no menses in \>12 months) or status post hysterectomy * Able to give informed consent Exclusion Criteria: * Presence of any one of the following medical conditions: chronic infection; chronic renal insufficiency; cancer other than skin cancer less than five years prior; multiple sclerosis or prior episode of central nervous system demyelination; or other chronic serious medical illnesses * Presence of any of the following on routine blood screening: WBC\<3000; Platelets \< 100,000; hematocrit \< 30%; BUN \> 30 mg %; creatine \> 1.5 mg%; liver disease with serum albumin \< 3 G/DL * Women who are pregnant or lactating * History of non-compliance with other therapies * Coexistence of other muscular disease * Drug or alcohol abuse within past three months * Known bleeding disorder * Known liver disease * Known congestive heart failure * Known hypernatremia * Inability to give informed consent