Avoiding Toxins Including Spermatotoxic Medications

Gillian Stearns, MD; Paul J. Turek, MD


Semin Reprod Med. 2013;31(4):286-292. 

In This Article



Nitrofurantoin was first shown to suppress spermatogenesis in animal models 60 years ago. Further studies linked its effect to the alteration of metabolism at the primary spermatocyte stage of spermatogenesis.[42] The most commonly cited work in men exposed to this drug showed temporary spermatogenic arrest in 7 of 30 patients and decreased sperm counts with no biopsy changes in another 6 patients.[42,43] Notably, the doses used in this study were higher than that currently recommended for effective antibiosis. At this time, no studies have examined for spermatogenic arrest at either 5 to 7 mg/kg/day dose or at suppressive dose of 1 to 2 mg/kg/day.[43] Men requiring antibiotic prophylaxis and desiring to conceive should be placed on alternative agents, if possible.


The effects of macrolides such as erythromycin on spermatogenesis and motility have been documented in animal and human studies. Studies of exposed rat testes showed decreased frequency of mitotic division that was reversible after stopping treatment. Short-term, high-dose exposure in humans was found to impair sperm motility or to be spermicidal. Long-term exposure to therapeutic doses of macrolides has not demonstrated pathological effects outside of animal models.[43] Currently, further research is needed to accurately determine the effects of macrolides on fertility.

Sulfa Antibiotics

Most sulfa drugs appear to have no negative effect on fertility. Studies examining sulfadiazine and sulfanilamide showed no alterations to the semen analysis after administration in humans.[43] However, sulfamethoxazole/trimethoprim was observed to decrease sperm counts in a study of 40 patients, but another study showed that sperm concentrations increased by 42%.[18,43,44] Yet another study indicated a possible effect on semen parameters among urologic and dermatologic patients, but the effects that were observed, including lower sperm count, motility, and abnormal morphology, were only noted 4 weeks after discontinuing the medication.[43] Further studies are needed to confirm any effects of sulfa antibiotics on human fertility.