Thalidomide in Rabbit Semen

Abstract

IT was found in an earlier study that when thalidomide is ingested by male rabbits over a period of weeks, the entire experimental dose not exceeding 2.5 g per animal, it exerts an unfavourable influence on their subsequent reproductive performance (refs. 1 and 2 and unpublished observations). Experiments comprising ten males and ninety females of proved high fertility indicated that while the breeding capacity in some of the treated males was much less seriously affected than in others, the overall untoward effect of prolonged intake of thalidomide expressed itself in seventy-two of 103 experimental matings as follows: in eighteen pregnancy failed to ensue, in twelve the number of young born was low, in twenty-five more than half the litter was lost by 14 days after birth, in eleven the young were grossly underweight at birth, and in six the young were malformed (spina bifida, absence of tail, cranial blister, absence of both kidneys, paralysis of hind limbs with lack of centres of ossification, and symmetrical haemangioma of the fore-limbs). To be seen in their proper light, these results must be set against the consistently high incidence of pregnancy in the rabbit colony, the excellent litter size and survival, and an incidence of spontaneous gross malformation of less than 1 per cent.