Key planning information

• Minimum order quantity is 3 kg, sufficient for feeding ~20 mice for one month.
• TD.130855-TD.130860 are available for quick shipment if irradiation is not needed. The typical lead time for other tamoxifen containing diets is two weeks (four weeks if irradiated).
• Irradiation must be requested at time of order.
• To place an order: contact Teklad Customer Service at 800.483.5523, tekladorders@inotiv.com, or initiate an order online.

Mice need time to adjust

Plan for:

• Initial weight loss of 10% is reported^1,2,3,4,5, associated with reduced food intake2 
• Daily observation of animal tolerance — consult your IACUC for monitoring metrics
• Intervene when necessary

References:

¹ Andersson KB, Winer LH, Mork HK, Molkentin JD, Jaisser F. 2010. Tamoxifen administration routes and dosage for inducible Cre-mediated gene disruption in mouse hearts. Transgenic Res 19:715-725.

² Chiang PM, Ling J, Jeong YH, Price DL, Aja SM, Wong PC. 2010. Deletion of TDP-43 down-regulates Tbc1d1, a gene linked to obesity, and alters body fat metabolism. Proc Natl Acad Sci USA 107:16320-16324.

³ Kiermayer C, Conrad M, Schneider M, Schmidt J, Brielmeier M. 2007. Optimization of spatiotemporal gene inactivation in mouse heart by oral application of tamoxifen citrate. Genesis 45:11-16.

⁴ Miro-Murillo M, Elorza A, Soro-Arnaiz I, Albacete-Albacete L, Ordonez A, Balsa E, Vara-Vega A, Vazquez S, Fuertes E, Fernandez-Criado C, Landazuri MO, Aragones J. 2011. Acute Vhl gene inactivation induces cardiac HIF-dependent erythropoietin gene expression. PLoS One 6:e22589.

⁵ Welle S, Burgess K, Thornton CA, Tawil R. 2009. Relation between extent of myostatin depletion and muscle growth in mature mice. Am J Physiol Endocrinol Metab.Oct;297(4):E935-40.

Other researchers have offered the following advice.

If intake seems to be a problem:

• Gradually acclimate mice by mixing tamoxifen-containing pellets with regular feed pellets
• Wet the food, then place in a dish inside the cage (requires daily replacement)
• Feed tamoxifen diet on weekdays, regular diet on weekends
• Alternate weeks (two weeks on tamoxifen diet, one week off) for longer treatments
• Determine if a lower dose is effective for your model

Safely managing tamoxifen diets

• Tamoxifen is a selective estrogen receptor modulator (SERM) meaning it can repress actions of estrogen or have pro-estrogen effects.
• Usual dose for therapeutic effects in humans is 20 mg/day. Tamoxifen diets for rodents typically contain ~one to two mg/pellet.
• Accidental tamoxifen exposure can be minimized by using typical lab precautions of lab coat, gloves, and mask when handling the diet.
• Your chemical safety department should be contacted for additional institution specific guidelines for handling and disposal of tamoxifen containing diets.

Key points from literature

• Tamoxifen diets are used to induce recombination in a variety of tissues and cell types for both functional gene expression modulation as well as lineage tracing experiments.
• Typical inclusion for pure tamoxifen is 250 mg or 500 mg per kg diet and for tamoxifen citrate is 400 mg per kg diet. This corresponds to ~40 and ~80 mg/kg body weight assuming 20-25 g body weight and intake of 3-4 g/day.
  • As food intake is reduced, dose will also be reduced.
  • There do not appear to be any differences in efficacy or tolerability between tamoxifen and tamoxifen citrate when absolute tamoxifen concentration is equal.
• The reported length of feeding varies from 1 day to up to 18 weeks 
  
  • The 500 mg tamoxifen/kg diet dose is typically used for 4 weeks or less.
• The age at which dietary tamoxifen has been initiated varies from as soon as weaning has occurred to well into the adult stage.
• Most of the references utilize one of the one of the stocked tamoxifen diets (TD.130855-TD.130860). However, TD.170935 is a modification of the 60% kcal from fat diet TD.06414 to include 400 ppm tamoxifen citrate. Tamoxifen can be included in virtually any diet; consult a nutritionist about inclusion in other custom diets.