Thalidomide, semen distribution, teratogenicity… and cost: reply from authors

Conflicts of interest none declared. Sir, Unfortunately, due to space limitations we could not address all possible issues concerning thalidomide use.1 However, we agree about the two concerns of the potential risk of thalidomide in male patients and of cost. It was demonstrated that thalidomide causes loss of elongating and round spermatids and degeneration of testicular germinal epithelium in the rabbit model.2 Further, thalidomide has been shown to be distributed into rabbit semen3 and human semen.4 Although one study showed congenital defects in newborn rabbits whose fathers were treated with thalidomide,3 a more recent study showed that males treated with thalidomide which were bred with untreated females resulted in no significant fetal alterations attributable to thalidomide.2 Thus, there is conflicting evidence in the rabbit model. There is no reported literature that human males treated with thalidomide may cause teratogenicity in an untreated female. However, as the threshold dose of thalidomide exposure causing birth defects is not known, it may be wise to err on the safe side and encourage males who are on thalidomide to use barrier contraception during and after 3 months of thalidomide therapy and to avoid sperm donation.