Study of the Pharmacokinetics of Intravenous Administered 14C-MNTX

An Open-Label, Phase I, Single Dose Study of the Pharmacokinetics, Mass Balance and Disposition of Intravenously Administered 14C-Methylnaltrexone in Normal, Healthy Volunteers

This is an open-label, radiotracer study, to be conducted in healthy, normal, male volunteers. It will entail intravenous administration of a single dose of 14C-MNTX, collection of excretions, and periodic drawing of blood samples. Exhaled 14CO2 will also be sampled as a measure of the extent of possible metabolic MNTX demethylation.

Inclusion Criteria:

1. Males between 18-45
2. Subject weight between 70 and 90 kg
3. In good physical health, with no evidence at screening of acute or chronic disease likely to affect the investigation

Exclusion Criteria:

1. History or evidence of cardiovascular, gastrointestinal, hepatic, neurological, pulmonary, renal, or other significant chronic condition.
2. Consumption of barbiturates or other inducers or inhibitors of CYP450 isoforms
3. History of or predisposition to erratic or abnormal bowel function.