An ideal anaesthetic should not possess hormonal activity nor should it interfere with the processes of reproduction. Althesin, a new intravenous anaesthetic, contains two steroids, alphaxalone (3α-hydroxy-5α-pregnane-11,20-dione) and alphadolone acetate (21-acetoxy-3α-hydroxy-5α-pregnane-11,20-dione) in 20% aqueous Cremophor EL (Badische Anilin und Soda Fabrik). Cremophor EL is polyoxyethylated castor oil, a non-ionic surface active agent. Althesin contains 9 mg alphaxalone and 3 mg alphadolone acetate/ml. The only endocrinological activity noted for Althesin has been a weak anti-oestrogenic effect in mice (Child, English, Gilbert & Woollett, 1972). Experiments have been undertaken to investigate whether the anaesthetic has any adverse effects on reproduction in rabbits. The results of similar studies on mice and rats have already been described (Child et al., 1972).
Rabbits of the Dutch breed were used. Each doe was mated two or three times in the course of a few hours