The purpose of this study is to determine if implitapide is effective in lowering triglyceride (TG) levels in patients with Fredrickson Type I or V hypertriglyceridemia where the maximum tolerable medication and diet were not sufficient.
Inclusion Criteria: In order to participate in this study, patients must meet all of the following inclusion criteria: * be between 8 and 70 years old with diagnosis of Fredrickson Type I or V HTG * be stable on current maximum tolerated triglyceride lowering therapy * have a fasting TG level of at least 880 mg/dL (10 mmol/L) * be male or nonpregnant, nonbreastfeeding female. The women in the study must be surgically sterile, postmenopausal or must practice an effective method of birth control * must be able to give informed consent or if under the age of 18, parents or legal guardians must give their informed consent * meet body weight requirements Exclusion Criteria: * Recent heart attack, coronary artery intervention, coronary bypass surgery, or stroke. * Patients with class 3 or 4 heart failure * Uncontrolled hypothyroidism or other uncontrolled endocrine disease * Known, clinically significant eye abnormalities, such as cataracts * History of hepatic disease or AST or ALT levels greater than 1.5 x ULN at Visit 1 * Alkaline phosphatase greater than 2 times ULN * Serum creatinine greater than 2.0 mg/dL * Liver cirrhosis and severe liver steatosis * Clinically significant infection, malignancy, or psychosis * Use of oral anticoagulants or digoxin unless the dose is stable and is regularly monitored * Participation in any other investigational study within the last 30 days * Breastfeeding or pregnant * Current drug or alcohol abuse * Serious or unstable medical conditions that would compromise the patient's safety or successful participation in the study * Unwillingness to comply with study procedures or unwillingness to cooperate fully