Tabex is NOT recommended while breastfeeding. We are copying here part of the manufacturer's warning:
Pregnancy and lactation: The intraovular application of Cytisine substance to hen embryos induced no embriotoxic and teratogenic effect within the limits of the single therapeutic doses. Higher doses of the drug lead to embryotoxic action. On the base of the experimental data obtained, Tabex is recommended (with Cytisine as the basic component) not to be taken by pregnant women, due to the potential risk of embryotoxic action in case of uncontrolled administration. The drug should not be administered during breast feeding.