Background:
The use of tamoxifen in mice requires prior IACUC approval. The following protocol should be considered when applying for IACUC approval.

Procedure:
Induction of Cre-ER can be achieved by IP, oral, or topical administration of tamoxifen. For IP and oral routes, tamoxifen should be dissolved in corn oil or sunflower oil at 10 mg/ml; for topical administration, it should be dissolved in ethanol/DMSO or emollient cream. Mice should be treated with 0.1 – 10 mg per 40 g mouse (IP or oral) or 0.5 – 100 mg per 40 g mouse (topical).

All procedures involving the use and administration of tamoxifen must be performed in a class 2 BSC hood. After administration of tamoxifen, the mice should be placed in a clean cage with a full size blue cage card placed in front of the regular cage card, which clearly states 1) “CHEMICAL HAZARD’ Tamoxifen, 2) relevant lab and contact name, 3) date of drug injection/administration and 4) Special handling until date (3 days after injections). The front edge of the lid should be taped shut with “chemical hazard” tape, as an extra precaution to ensure awareness of the need for special handling 3 days post-drug administration. All such cages should then be placed at the bottom of the side of the rack closest to the clean room door. When necessary, the cages must be opened only in a class 2 BSC hood and all dirty bedding, etc. disposed of in yellow bags and discarded in fiber drums designated for incineration. All procedures must be conducted in consultation with DLAR staff.

After drug administration, lab members must observe the mice daily for 5 days for any signs of pain and discomfort (including but not limited to weight loss, reduced mobility, hunching, and respiratory distress). If signs of distress are noted, the animal should be euthanized, or an attempt must be made to alleviate pain/discomfort in a manner appropriate to the circumstances. Such cases should be discussed with DLAR staff to determine the appropriate course of action. All contaminated bedding, etc. must be disposed as described above. If the animals are removed from the facility for experiments, all handling of the open cages must be done in a class 2 BSC hood and feces disposed of in “biohazard” (yellow) bags and discarded in fiber drums designated for incineration before returning the transfer container back to the facility for washing. All procedures will be conducted in consultation with NYU DLAR and Environmental Services staff.

After administration of tamoxifen, all surfaces must be decontaminated immediately. All contaminated disposable materials, such as feeding tubes, should be disposed of in biohazard bags. For at least 3 days following administration of tamoxifen, animal caretakers should handle relevant animals and cages as described above. Once dirty bedding is removed from cages that housed mice given tamoxifen, the cages themselves do not require further special handling. Dead animals that have been administered tamoxifen should be discarded in designated drums for incineration, as are all animals in the Skirball animal facility.

Note that tamoxifen metabolism is hepatic, with excretion of metabolites largely restricted to the feces. Metabolite excretion continues for 2 days post-administration; therefore, care must be taken in the disposal of dirty bedding for 72 h after administration. Once the 3 d period after the last injection of tamoxifen has past, animals should be moved to clean cages. After this period, no special handling of the bedding, cages or animals is required