Formulation and administration of triclocarban.

All dose formulations contained [¹⁴C]triclocarban and unlabeled triclocarban to achieve the final desired triclocarban concentration and specific activity. The target radioactivity per animal was ~ 50 μCi/rat and 10 μCi/mouse. Oral formulations were prepared by first dissolving both [¹⁴C]triclocarban and unlabeled triclocarban in acetone. The acetone was removed by rotary evaporation in a tare-weighed round bottom flask. The flask was reweighed to ensure that all the acetone was removed. An appropriate amount of the resulting [¹⁴C]triclocarban was weighed and dissolved in corn oil to prepare gavage formulations or in acetone to prepare dermal formulations. A single oral dose was administered in a volume of 5 mL/kg for rat and 10 mL/kg for mouse by intragastric gavage. Dermal dose formulations were prepared similarly in acetone. A single dermal dose was applied at 0.5 mL/kg for rat and 1.25 mL/kg for mouse. The dermal doses were applied onto a 4 cm² (2 cm x 2 cm) for rats (1 cm² for mice) area of skin on the animals’ backs. Approximately 24 h prior to dosing, animals were anesthetized with isoflurane by inhalation. Fur was clipped from the animals’ backs and the clipped area was wiped with a wet gauze, dried, and then examined for nicks. Any animals with nicks in the clipped area were excluded from the study. The outline of the dosing area was inscribed on the animal with a permanent-type felt tip marker. The animals were then placed in individual metabolism cages for overnight acclimation. Prior to dosing rats, a protective foam appliance was glued onto the rats’ backs using Hollister’s Medical Adhesive. The dermal doses were administered evenly to the dose area using a blunt device (Hamilton® syringe fitted with a 20-gauge ball-tipped feeding needle) and spread as evenly as possible over the dose site. A non-occlusive cloth cover was attached over the appliance prior to returning the rat to its cage. For mice, a metal mesh appliance was secured over the dose site with cyanoacrylate glue following dose administration as described for rats. For dermal dose groups designated for no protective appliance, doses were administered as described with the omission of the appliance. After dosing all animals were returned to metabolism cages.

The concentration of [¹⁴C]triclocarban in the dose formulations was determined by LSS analysis of weighed aliquots of formulations collected before, during, and after dosing for a total of five aliquots sampled on the day of dosing. Radiochemical purity of each formulation was assessed using HPLC Method 2 on the day of dosing and was ≥ 97.7%.