Study of SSP-004184 (SPD602) in Healthy Adults and Subjects With Impaired Liver Function

Inclusion Criteria: * Age 18-65 years inclusive at the time of consent. * Willingness to comply with any applicable contraceptive requirements of the protocol and is: * Male, or * Non pregnant, non lactating female * Females must be at least 90 days post partum or nulliparous. Subjects who do not have hepatic impairment (healthy subjects) * Normal renal function. Subjects with hepatic impairment * Subjects must provide a letter of evaluation from a hepatologist or copy of supporting documents confirming the subject's hepatic impairment (a liver biopsy is preferable but not mandatory). * Hepatic impairment should be primary and must not be a complication of an underlying primary systemic disease (eg, patients with metastatic cancer and cancer cachexia) * Documented chronic stable liver impairment Exclusion Criteria Subjects who do not have hepatic impairment (healthy subjects) * A positive HIV antibody screen, Hepatitis B surface antigen, or Hepatitis C virus antibody screen. Subjects with hepatic impairment * Presence of a hepatocellular carcinoma, or an acute hepatic disease caused by an infection or drug toxicity. * Presence of surgically created or transjugular intrahepatic portal systemic shunts. * A positive HIV antibody screen. * Renal insufficiency. All subjects * Subject has a history of thyroid disorder. * History of nephrotic syndrome. * History of alcohol or other substance abuse within the last year. * A positive screen for alcohol or drugs of abuse. * Male subjects who consume more than 3 units of alcohol per day. Female subjects who consume more than 2 units of alcohol per day. (1 alcohol unit = 1 beer \[12 oz/355 mL\] = 1 wine \[5 oz/150 mL\] = 1 liquor \[1.5 oz/40 mL\] = 0.75 oz/20 mL alcohol.) * Caffeine consumption: For healthy subjects: Routine consumption of more than 2 units of caffeine per day or subjects who experience caffeine withdrawal headaches or have a history of caffeine withdrawal headaches. (One caffeine unit is contained in the following items: one 6 oz/180 mL cup of coffee, two 12 oz/355 mL (ie, 24 oz/710 mL cola) cans of cola, one 12 oz/355 mL cup of tea, three 1 oz/28 g chocolate bars (ie, 3 oz/85 g chocolate). Decaffeinated coffee, tea, or cola are not considered to contain caffeine.) * Donation of blood or blood products within 60 days. * Substantial changes in eating habits within 30 days.