Tamoxifen free base seems most frequently to be given in corn oil i.p. in, for example, CreER conditional KO mice. We have routinely used tamoxifen citrate which can be formulated in aqueous vehicles for i.p. injections (such as 0.5% methycellulose). In our experience this protocol is much more humane for the mice, and the citrate salt can be dosed at between 5 and 20mg/kg, rather than the 100mg/kg or more frequently used for the free base. Oral dosing leads to lower bioavailability, and mice don't like tamoxifen food pellets and in some cases will refuse to eat them at all.

Is the use of tamoxifen citrate just not well known as an alternative protocol?